Maharashtra Board Class 10 Science Chapter 8 Metallurgy Solutions

Std 10 Science Part 1 Chapter 8 Metallurgy Question Answer Maharashtra Board

Class 10 Science Part 1 Chapter 8 Metallurgy Question Answer Maharashtra Board

Question 1. a. Alloy of sodium with mercury.
Answer: Silver amalgam.
In simple words: Silver amalgam is an alloy formed by mixing sodium with mercury. It is typically a liquid at room temperature.

🎯 Exam Tip: Remember common alloys and their constituent metals, as they are frequently asked in exams.

Question 1. b. Molecular formula of common ore of aluminium.
Answer: Al2O3.nH2O
In simple words: The most common ore of aluminum is bauxite, which is a hydrated aluminum oxide. Its formula indicates aluminum oxide combined with water molecules.

🎯 Exam Tip: Knowing the chemical formulas of important ores is crucial for scoring well in chemistry sections.

Question 1. c. The oxide that forms salt and water by reacting with both acid and base.
Answer: Aluminium oxide (Al2O3).
In simple words: Aluminum oxide is an amphoteric oxide, meaning it can act as both an acid and a base, reacting with strong acids to form salt and water, and similarly with strong bases.

🎯 Exam Tip: Amphoteric oxides like aluminum oxide and zinc oxide are important concepts to understand for their dual reactivity.

Question 1. d. device used for grinding an ore.
Answer: The device used for grinding an ore is grinding mill.
In simple words: A grinding mill is a machine specifically designed to crush and pulverize ores into fine particles, which is often the first step in metal extraction processes.

🎯 Exam Tip: Understanding the basic equipment used in the initial stages of metallurgy helps in grasping the overall process.

Question 1. e. The nonmetal having electrical conductivity.
Answer: Graphite having electrical conductivity.
In simple words: Graphite, an allotrope of carbon, is unique among nonmetals for its ability to conduct electricity due to the presence of delocalized electrons within its layered structure.

🎯 Exam Tip: Exceptions to general rules, like graphite's conductivity among nonmetals, are common exam questions.

Question 1. f. The reagent that dissolves noble metals.
Answer: Aqua regia is the reagent that dissolves noble metals like gold and platinum.
In simple words: Aqua regia is a highly corrosive mixture of concentrated nitric acid and hydrochloric acid, famous for its ability to dissolve noble metals that single acids cannot.

🎯 Exam Tip: Learn the composition and unique property of aqua regia, as it's a key concept related to noble metals.

Question 2. Make pairs of substances and their properties.

Column I	Column II
Substance	Property
(1) Potassium bromide	(a) Combustible
(2) Gold	(b) Soluble in water
(3) Sulphur	(c) No chemical reaction
(4) Neon	(d) High ductility
	(e) Magnetic ingredient

Answer:
(1) Potassium bromide - Soluble in water
(2) Gold - High ductility
(3) Sulphur - Combustible
(4) Neon - No chemical reaction
In simple words: This question tests your knowledge of the characteristic properties of different substances like ionic compounds (Potassium bromide), metals (Gold), nonmetals (Sulphur), and noble gases (Neon). Matching each substance to its correct property is key.

🎯 Exam Tip: Understand the fundamental properties of different types of elements and compounds to accurately match them in such questions.

Question 3. Identify the pairs of metals and their ores from the following.

Column I (ores)	Column II (metals)
(1) Bauxite	(a) Mercury
(2) Cassiterite	(b) Aluminium
(3) Cinnabar	(c) Tin
	(d) Copper

Answer:
(1) Bauxite - Aluminium
(2) Cassiterite - Tin
(3) Cinnabar - Mercury
In simple words: This matching exercise connects specific ores with the metals that are primarily extracted from them, illustrating common natural sources of different metals.

🎯 Exam Tip: Memorizing the names of important ores and their corresponding metals is essential for metallurgy questions.

Question 4. Explain the terms. a. Metallurgy
Answer: Metallurgy: The process used for extraction of metals in their pure form from their ores, then metals are further purified by different methods of purification. All the process is called metallurgy.
In simple words: Metallurgy is the science and technology involved in extracting metals from their natural ores and then refining them into usable forms. It covers everything from mining to purification.

🎯 Exam Tip: A clear, concise definition of key terms like 'metallurgy' is important for foundational understanding.

Question 4. b. Ores.
Answer: Ores: The minerals from which metals are extracted profitably and conveniently are called ores.
Examples: Bauxite (Al2O3.H2O), Cinnabar (HgS).
In simple words: Ores are naturally occurring rocks or minerals that contain a valuable metal or element that can be extracted economically. They are the primary source for industrial metal production.

🎯 Exam Tip: Differentiate clearly between minerals and ores, and be ready to provide examples of common ores.

Question 4. c. Minerals.
Answer: Minerals: The naturally occurring compounds of metals along with other impurities are known as minerals.
Examples: Rocks are composed of mixtures of minerals. Talc and granite are minerals.
In simple words: Minerals are naturally occurring solid substances with a definite chemical composition and a characteristic crystal structure, often containing metals along with various impurities.

🎯 Exam Tip: Understand that all ores are minerals, but not all minerals are ores (only those from which metal can be profitably extracted).

Question 4. d. Gangue.
Answer: Gangue: Ores contain metal compounds with some of the impurities like soil, sand, rocky material, etc. These impurities are called gangue.
In simple words: Gangue refers to the unwanted earthy or rocky impurities found naturally mixed with the valuable mineral in an ore. It must be removed before metal extraction.

🎯 Exam Tip: Knowing the term 'gangue' and its significance in the ore concentration process is fundamental to metallurgy.

Question 5. Write scientific reasons. a. Lemon or tamarind is used for cleaning copper vessels turned greenish.
Answer:
- Copper undergoes oxidation in air to form black copper oxide. Copper oxide reacts slowly with carbon dioxide in air and gains a green coat. This green substance is copper carbonate.
- Lemon and tamarind contain acid. The acid dissolves the green coating of basic copper carbonate present on the surface of a tarnished copper utensil and makes it shiny again.
In simple words: Copper vessels turn green due to the formation of basic copper carbonate from reaction with moist air. Lemon or tamarind, being acidic, react with and dissolve this green layer, cleaning the vessel.

🎯 Exam Tip: This illustrates a practical application of acid-base reactions in daily life, often tested in context of corrosion.

Question 5. b. Generally the ionic compounds have high melting points.
Answer:
- The ionic compounds exist in solid state and are hard due to strong electrostatic force of attraction between oppositely charged ions.
- The intermolecular force of attraction is high in ionic compounds and large energy is required to overcome it. Therefore, ionic compounds have high melting points.
In simple words: Ionic compounds are held together by strong electrostatic forces between positively and negatively charged ions. A large amount of energy is needed to break these strong bonds, resulting in high melting points.

🎯 Exam Tip: Connect high melting points of ionic compounds to the strength of their electrostatic forces of attraction between ions.

Question 5. c. Sodium is always kept in kerosene. (OR) Why is sodium stored in kerosene?
Answer:
- Sodium reacts so vigorously with atmospheric oxygen that it catches fire if kept in the open.
- It does not react with kerosene and sinks in it. Hence, to protect sodium and to prevent accidental fires it is always kept in kerosene.
In simple words: Sodium is a highly reactive metal that reacts explosively with oxygen and moisture in the air. Kerosene, being non-reactive and less dense than sodium, provides a protective layer, preventing contact with air and water.

🎯 Exam Tip: This is a classic example of a reactive metal's storage, emphasizing its chemical properties and safety measures.

Question 5. d. Pine oil is used in the froth floatation process.
Answer:
- In the concentration of an ore by froth floatation process, the ore is mixed with water and pine oil. When air is bubbled through the mixture a froth is formed.
- The mineral particles in the ore are preferentially wetted by the oil and float on the top in the froth.
- The gangue particles are wetted by water and settle down. Thus the mineral can be separated from the gangue and the ore is concentrated.
In simple words: Pine oil is used in froth floatation because it selectively wets the desired mineral particles, making them hydrophobic. This allows them to attach to air bubbles and float as froth, separating them from water-wetted gangue.

🎯 Exam Tip: Focus on the selective wetting property of pine oil and its role in separating hydrophobic mineral particles from hydrophilic gangue.

Question 5. e. Anodes need to be replaced from time to time during the electrolysis of alumina.
Answer:
- During electrolysis of alumina, the oxygen liberated at the carbon anode reacts with graphite rods (carbon anode) and forms carbon dioxide.
- As the anodes get oxidised during electrolysis of alumina, they are continuously eroded. Hence, it is necessary to replace anodes from time to time.
In simple words: In alumina electrolysis, oxygen gas is produced at the carbon anodes, which then reacts with the carbon to form carbon dioxide. This continuous reaction consumes and erodes the anodes, necessitating their regular replacement.

🎯 Exam Tip: This question highlights a practical challenge and its chemical explanation in the industrial extraction of aluminum.

Question 6. When a copper coin is dipped in silver nitrate solution, a glitter appears on the coin after some time. Why does this happen? Write the chemical equation.
Answer: When a copper coin is dipped in a silver nitrate solution, more reactive copper displaces silver from silver nitrate solution. The silver so liberated deposits on the copper coin. As a result, a shiny coat of silver is formed on the coin.
\( \text{Cu(s) + 2AgNO}_3\text{(aq)} \rightarrow \text{Cu(NO}_3\text{)}_2\text{(aq)} + \text{2Ag(s)} \)
In simple words: Copper is more reactive than silver, so it displaces silver from silver nitrate solution. The displaced silver then deposits as a shiny coating on the copper coin, causing it to glitter.

🎯 Exam Tip: This is an excellent example of a displacement reaction based on the reactivity series of metals. Remember to write balanced chemical equations.

Question 7. The electronic configuration of metal 'A' is 2, 8, 1 and that of metal 'B' is 2, 8, 2. Which of the two metals is more reactive? Identify these metals. Write their reaction with dilute hydrochloric acid. (Practice Activity Sheet – 1)
Answer: If the number of electrons in the outermost orbit is less, then the metal is more reactive. Metal A contains one electron in the outermost shell, while metal B contains two electrons. Hence, metal A is more reactive than metal B.
Metal A is sodium and metal B is magnesium. Reactions of Na and Mg with dil. HCI are,
\( \text{2Na}_{\text{(Sodium)}} + \text{2HCl}_{\text{(dil. HCl)}} \rightarrow \text{2NaCl}_{\text{(aq)}} + \text{H}_2\text{(g)}_{\text{(Hydrogen)}} \)
\( \text{Mg}_{\text{(Magnesium)}} + \text{2HCl}_{\text{(dil. HCl)}} \rightarrow \text{MgCl}_2 + \text{H}_2\text{(g)}_{\text{(Hydrogen)}} \)
In simple words: Metal A (Sodium) is more reactive than Metal B (Magnesium) because it has fewer valence electrons, making it easier to lose electrons and react. Both metals react with dilute hydrochloric acid to produce hydrogen gas and their respective chloride salts.

🎯 Exam Tip: Reactivity of metals is often correlated with their electronic configuration (ease of losing electrons). Practice writing balanced equations for metal-acid reactions.

Question 8. Draw a neat labelled diagram. a. Magnetic separation method.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र चुंबकीय पृथक्करण विधि को दर्शाता है। इसमें एक कन्वेयर बेल्ट होता है जो दो रोलर्स (एक चुंबकीय और एक गैर-चुंबकीय) के चारों ओर घूमता है। पिसा हुआ अयस्क बेल्ट पर डाला जाता है, और चुंबकीय सामग्री चुंबकीय रोलर के पास गिर जाती है जबकि गैर-चुंबकीय सामग्री दूर गिरती है, जिससे अयस्क से अशुद्धियों को अलग किया जाता है।
In simple words: The magnetic separation method uses a magnetic roller to separate magnetic ore particles from non-magnetic impurities. As powdered ore moves over the belt, magnetic components are attracted and fall closer to the roller, while non-magnetic parts are flung further away.

🎯 Exam Tip: For diagrams, focus on clear labels and understanding the principle of separation (e.g., magnetic property) rather than artistic drawing skill.

Question 8. b. Forth floatation.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख झाग प्लवन विधि को दर्शाता है, जिसका उपयोग सल्फाइड अयस्कों के सांद्रण के लिए किया जाता है। पिसे हुए अयस्क, पानी और पाइन तेल के मिश्रण में हवा डाली जाती है, जिससे अयस्क कण झाग के साथ ऊपर तैरते हैं जबकि अशुद्धियाँ नीचे बैठ जाती हैं, जिससे अयस्क का सांद्रण होता है।
In simple words: Froth floatation is a process for concentrating sulfide ores where powdered ore is mixed with water and pine oil. Air is bubbled through, creating froth where mineral particles, preferentially wetted by oil, float to the surface and are collected.

🎯 Exam Tip: Key components to label and understand in froth floatation are the air supply, agitator, froth, concentrated ore, and gangue, along with the role of pine oil.

Question 8. c. Electrolytic reduction of alumina.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एल्यूमिना के विद्युत अपघटनी अपचयन को दर्शाता है, जो एल्यूमीनियम के निष्कर्षण की एक विधि है। इसमें ग्रेफाइट लाइनों वाला एक स्टील टैंक होता है जो कैथोड के रूप में कार्य करता है, और ग्रेफाइट रॉड एनोड के रूप में कार्य करती हैं। पिघला हुआ एल्यूमिना, क्रायोलाइट और फ्लूओर्सपार का मिश्रण इलेक्ट्रोलाइट के रूप में उपयोग किया जाता है, और पिघला हुआ एल्यूमीनियम टैंक के निचले हिस्से से एकत्र किया जाता है।
In simple words: The electrolytic reduction of alumina diagram shows the setup for aluminum extraction. It involves a steel tank lined with graphite (cathode) and graphite rods (anodes) immersed in molten alumina, cryolite, and fluorspar, where aluminum is deposited at the bottom.

🎯 Exam Tip: Understand the roles of the anode, cathode, electrolyte (alumina, cryolite, fluorspar mixture), and the collection of molten aluminum in this industrial process.

Question 8. d. Hydraulic separation method.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख हाइड्रोलिक पृथक्करण विधि को दर्शाता है, जिसका उपयोग अयस्क से अशुद्धियों को अलग करने के लिए किया जाता है। इसमें एक शंक्वाकार टैंक होता है जिसमें ऊपर से पिसा हुआ अयस्क डाला जाता है और नीचे से पानी का तीव्र प्रवाह प्रवेश करता है। भारी अयस्क कण नीचे बैठ जाते हैं जबकि हल्के गैंग्यू कण पानी के साथ बह जाते हैं, जिससे अयस्क का सांद्रण होता है।
In simple words: The hydraulic separation method uses a strong current of water to separate heavy ore particles from lighter gangue. Powdered ore is introduced into a tapering tank, and water flow carries away the lighter impurities while heavier ore settles.

🎯 Exam Tip: Focus on how the difference in density between ore and gangue is utilized with flowing water for separation in this method.

Question 9. Write chemical equation for the following events. a. Aluminium came in contact with air.
Answer: When aluminium is exposed to air, it develops a thin oxide layer of aluminium.
\( \text{4Al}_{\text{(Aluminium)}} + \text{3O}_2_{\text{(Oxygen)}} \xrightarrow{\text{heat}} \text{2Al}_2\text{O}_3_{\text{(Aluminium oxide)}} \)
In simple words: When aluminum is exposed to air, it reacts with oxygen to form a thin, protective layer of aluminum oxide, preventing further corrosion.

🎯 Exam Tip: This equation represents the passive nature of aluminum due to its oxide layer. Ensure balancing of the chemical equation.

Question 9. b. Iron filings are dropped in aqueous solution of copper sulphate.
Answer: When iron filings are dropped in copper sulphate solution, more reactive iron displaces copper from copper sulphate solution. The iron filings get coated with reddish brown copper metal and the blue colour of copper sulphate fades gradually and ferrous sulphate is formed.
\( \text{Fe}_{\text{(s) (Blue)}} + \text{CuSO}_4_{\text{(aq)}} \rightarrow \text{FeSO}_4_{\text{(aq) (Colourless)}} + \text{Cu}_{\text{(s) (Copper)}} \)
In simple words: Iron, being more reactive than copper, displaces copper from copper sulfate solution. This results in the formation of colorless ferrous sulfate and a reddish-brown coating of copper on the iron filings.

🎯 Exam Tip: This is a classic displacement reaction. Pay attention to the color changes and the reactivity series to predict products.

Question 9. c. A reaction was brought about between ferric oxide and aluminium.
Answer: The reaction between ferric oxide and iron produces aluminium oxide and iron. It is a thermite reaction and is highly exothermic.
It produces a large amount of heat, which is released to melt oxygen and aluminium. This reaction is used in welding of machineries. It is also used in warfare to make grenades.
The chemical reaction for the above is as follows:
\( \text{3Fe}_3\text{O}_2 + \text{4Al} \rightarrow \text{2Al}_2\text{O}_3 + \text{6Fe} \)
In simple words: The thermite reaction involves ferric oxide reacting with aluminum powder, releasing a massive amount of heat to produce molten iron and aluminum oxide. This highly exothermic reaction is used in welding and incendiary devices.

🎯 Exam Tip: The thermite reaction is important due to its industrial applications (welding) and its highly exothermic nature. Remember the reactants and products.

Question 9. d. Electrolysis of alumina is done.
Answer: During electrolysis of alumina, aluminium is deposited at the cathode. Molten aluminium being heavier than the electrolyte, is collected at the bottom of the tank. Oxygen gas is liberated at the anode.
Anode reaction: \( \text{2O}^{2-} \rightarrow \text{O}_2 + \text{4e}^- \text{ (Oxidation)} \)
Cathode reaction: \( \text{Al}^{3+} + \text{3e}^- \rightarrow \text{Al(l) (Reduction)} \)
In simple words: Electrolysis of alumina produces molten aluminum at the cathode and oxygen gas at the anode. The aluminum, being denser, settles at the bottom of the electrolytic cell.

🎯 Exam Tip: For electrolysis, correctly identifying anode/cathode reactions (oxidation/reduction) and the products formed is crucial.

Question 9. e. Zinc oxide is dissolved in dilute hydrochloric acid.
Answer: Zinc oxide is dissolved in dilute hydrochloric acid, zinc chloride and water are formed.
\( \text{ZnO}_{\text{(s) (Zinc oxide (basic oxide))}} + \text{2HCl}_{\text{(l)}} \rightarrow \text{ZnCl}_2_{\text{(aq) (Zinc chloride)}} + \text{H}_2\text{O}_{\text{(l)}} \)
In simple words: When zinc oxide, a basic oxide, reacts with dilute hydrochloric acid, it forms zinc chloride salt and water.

🎯 Exam Tip: This reaction is a neutralization reaction between a basic oxide and an acid. Understand that zinc oxide is amphoteric, meaning it can react with both acids and strong bases.

Question 10. Complete the following statement using every given options. During the extraction of aluminium a. Ingredients and gangue in bauxite. b. Use of leuching during the concentration of ore. c. Chemical reaction of transformation of bauxite into alumina by Hall's process. d. Heating the aluminium ore with concentrated caustic soda.
Answer: c. Chemical reaction of transformation of bauxite into alumina by Hall's process.
In simple words: This question asks about a specific step in aluminum extraction. The correct option identifies the chemical transformation of bauxite into alumina as part of Hall's process.

🎯 Exam Tip: Pay attention to the specific processes and their names, like Hall's process, which are critical in metallurgy.

Question 11. Divide the metals Cu, Zn, Ca, Mg, Fe, Na, Li into three groups, namely, reactive metals, moderately reactive metals and less reactive metals.
Answer: Reactive metals: Na, Li, Ca
Moderately reactive metals: Zn, Fe, Mg,
Less reactive metals: Cu
In simple words: Metals are categorized by their reactivity; Sodium, Lithium, and Calcium are highly reactive; Zinc, Iron, and Magnesium are moderately reactive; and Copper is a less reactive metal.

🎯 Exam Tip: Knowing the reactivity series of metals is fundamental. Be able to classify common metals into these categories.

Question 1. what are the physical properties of metals and nonmetals?
Answer: Properties of metals:
1. Solid state (Exception: Mercury and gallium)
2. Typical lustre
3. Malleability and ductility
4. Hardness (Exception: Lithium, sodium and potassium)
5. Good conductors of heat and electricity
6. High melting and boiling points (On the other hand, the melting and boiling points of the metals sodium, potassium, mercury and galium are very low.)
7. Sonorous and produce sound on striking a hard surface.
Properties or nonmetals:
1. Gaseous or solid state (Exception: Bromine in liquid state)
2. Lack of any typical lustre (Exception: Iodine and Diamond)
3. Brittleness in the solid state (Exception: Diamond is the hardest natural substance)
4. Bad conductors of heat and electricity (Exception: Graphite) (Diamond is good conductor of heat)
5. Low melting and boiling points.
In simple words: Metals typically are solid, lustrous, malleable, ductile, good conductors of heat and electricity, and have high melting points, with some exceptions. Nonmetals are generally gases or solids (except bromine), lack luster, are brittle, poor conductors, and have low melting points, also with exceptions like diamond and graphite.

🎯 Exam Tip: Be prepared to list and compare the physical properties of metals and nonmetals, including their common exceptions.

Question 1. What is the electronic definition of oxidation and reduction?
Answer: When a metal loses electrons the process is called an oxidation while when a nonmetal gains electrons, it is called a reduction,
\( \text{Na} \rightarrow \text{Na}^+ + \text{e}^- \text{ (oxidation)} \)
\( \text{Cl}^- + \text{e}^- \rightarrow \text{Cl (reduction)} \)
In simple words: Oxidation is defined as the loss of electrons, typically by metals, resulting in a positive charge. Reduction is the gain of electrons, often by nonmetals, leading to a more negative charge.

🎯 Exam Tip: Remember "LEO goes GER" (Loss of Electrons is Oxidation, Gain of Electrons is Reduction) as a mnemonic for these fundamental definitions.

Question 1. What is meant by corrosion?
Answer: Corrosion is degradation of a material due toreaction with its environment.
In simple words: Corrosion is the natural process where materials, typically metals, deteriorate and wear away due to chemical reactions with their surrounding environment, often involving oxygen and moisture.

🎯 Exam Tip: A clear definition of corrosion is essential. Be able to relate it to rusting of iron as a specific example.

Question 2. Have you observed the following things? (1) Old iron bars in the builthngs.
Answer: When old iron bars in the buildings are exposed to moist air for a long time, they acquire a coating of browm nlaky substance called rust. (Fe2O3.H2O)
In simple words: Old iron bars develop a reddish-brown, flaky coating called rust (hydrated iron(III) oxide) when exposed to moist air over time.

🎯 Exam Tip: Rusting is a common example of corrosion of iron; knowing its chemical formula and conditions is important.

Question 2. (2) Copper vessels not cleaned for a long time.
Answer: If copper vessels are not cleaned for a long time, they react with moist carbon dioxide in the air, lose their shine and gain a green coat of copper carbonate. (CuCO3)
In simple words: Uncleaned copper vessels react with moist carbon dioxide in the air to form a green layer of copper carbonate, causing them to lose their original shine.

🎯 Exam Tip: This illustrates a specific type of corrosion for copper, which forms a green patina (copper carbonate).

Question 3. Silver ornaments or idols exposed to air for a long time.
Answer: When silver ornaments or idols are kept exposed to air for a long time, silver reacts with sulphur in the air to form a coating of black silver sulphide. (Ag2S)
In simple words: Silver ornaments tarnish over time when exposed to air, reacting with sulfur compounds to form a black layer of silver sulfide.

🎯 Exam Tip: Know that silver tarnishes due to reaction with hydrogen sulfide (a sulfur compound) in the air, forming black silver sulfide.

Question 4. Old vehicles fit to be thrown away.
Answer: The metallic parts of the body of old cars are corroded, eaten up and sometimes become perforated. The old cars also lose the original colour due to formation of flakes of rust.
In simple words: Old vehicles often show significant corrosion on their metallic parts, leading to structural damage and loss of original paint, primarily due to rust formation.

🎯 Exam Tip: This is a real-world example of extensive corrosion, highlighting its destructive impact on metallic structures.

Question 1. In the reaction between chlorine and HBr a transformation or HBr into Br2 takes place. Can this transformation be called oxidation? What Is the oxidant that brings about this oxidation?
Answer: The conversion of HBr to Br2 is an oxidation process. In the above reaction, Cl2 in the oxidant.
In simple words: Yes, the transformation of HBr to Br2 is an oxidation because bromine's oxidation state increases from -1 to 0. Chlorine (Cl2) acts as the oxidant, causing this change.

🎯 Exam Tip: To identify oxidation/reduction, track changes in oxidation states. The oxidant is the substance that gets reduced (gains electrons).

Question 1. what are the moderately reactive metals?
Answer: In the middle of the reactivity series, metals such as iron. zinc, lead, copper are moderately reactive.
In simple words: Moderately reactive metals, like iron, zinc, lead, and copper, are found in the middle of the reactivity series, meaning they are less reactive than alkali metals but more reactive than noble metals.

🎯 Exam Tip: Familiarize yourself with the reactivity series to correctly classify metals based on their reactivity.

Question 2. In which form to the moderately reactive metals occur in nature?
Answer: The moderately reactive metals which occur in nature are in the form of their sulphide salts or carbonate salts.
In simple words: Moderately reactive metals are typically found in nature as their sulfide ores (e.g., zinc sulfide) or carbonate ores (e.g., iron carbonate).

🎯 Exam Tip: Knowing the common forms of ores for different reactivity groups of metals is important for understanding extraction processes.

Question 1. Why do silver articles turn blackish while copper vessels turn greenish on keeping in air for long time?
Answer:
1. Silver articles turn blackish on exposure to air for a long time. This is because of silver sulphide (Ag2S) layer formed on the silver articles by the reaction of silver with hydrogen sulphide.
2. Carbon dioxide in moist air reacts with copper vessel. Copper loses its lustre due to formation of greenish layer of copper carbonate (CuCO3) on its surface.
In simple words: Silver articles turn black due to reaction with hydrogen sulfide in the air forming silver sulfide, while copper vessels turn greenish from reacting with moist carbon dioxide to form copper carbonate.

🎯 Exam Tip: Be able to explain the specific chemical reactions and products responsible for tarnishing in silver and copper.

Question 2. Why do pure gold and platinum always glitter?
Answer: Gold and platinum are noble metals as they do not react with moisture, O2 and CO2 from air also acids and alkalis, therefore, pure gold and platinum always glitter.
In simple words: Pure gold and platinum are known as noble metals because they are highly unreactive and do not corrode or tarnish when exposed to air, moisture, acids, or alkalis, thus maintaining their natural luster.

🎯 Exam Tip: The unreactive nature of noble metals is key to their stability and why they retain their shine.

Question 1. Write the electrode reaction for electrolysis of molten magnesium chloride and calcium chloride.
Answer: (1) Magnesium chloride (MgCl2):
\( \text{MgCl}_2 \rightarrow \text{Mg}^{2+} + \text{2Cl}^- \)
At the cathode: \( \text{Mg}^{2+} + \text{2e}^- \rightarrow \text{Mg} \)
At the anode: \( \text{2Cl}^- \rightarrow \text{Cl}_2 + \text{2e}^- \)
(2) Calcium chloride (CaCl2):
At the cathode: \( \text{Ca}^{2+} + \text{2e}^- \rightarrow \text{Ca} \)
At the anode: \( \text{2Cl}^- \rightarrow \text{Cl}_2 + \text{2e}^- \)
In simple words: During the electrolysis of molten magnesium chloride or calcium chloride, metal ions (Mg2+ or Ca2+) gain electrons at the cathode to form pure metal, while chloride ions lose electrons at the anode to form chlorine gas.

🎯 Exam Tip: Remember that in molten salt electrolysis, cations are reduced at the cathode and anions are oxidized at the anode. Balancing charges and elements in the half-reactions is essential.

Question 1. Which measures would you suggest to stop the corrosion of metallic articles or not allow the corrosion to start?
Answer: Various types of methods are used to protect metals from corrosion. Almost in all the methods, special attention is paid so that iron does not rust. It is possible to lower the rate of the process of rusting of iron. Corrosion of metals can be stopped by detaching the air from metals.
Some methods are as follows :
1. To fix a layer of some substance on the metal surface so that the contact of the metal with moisture and oxygen in the air is prevented and no reaction would occur between them.
In simple words: To prevent corrosion, various methods aim to block the metal's contact with air and moisture. This can be achieved by applying a protective layer, such as paint, oil, or grease, or by coating it with another substance.

🎯 Exam Tip: Understand the basic principle of corrosion prevention: isolating the metal from corrosive agents like oxygen and moisture.

 

Question 2. What is done so to prevent rusting of iron windows and iron doors of your house?
Answer: To prevent rusting of iron windows and iron doors in the house, they are painted so that they do not rust.
In simple words: Painting iron windows and doors creates a barrier that prevents moisture and oxygen from reaching the metal, thus stopping rust.

🎯 Exam Tip: Focus on understanding the barrier protection principle behind painting as a corrosion prevention method.

 

Question 3. What is done so to prevent rusting or iron windows and iron doors of your house?
Answer: To prevent rusting of iron windows and iron doors in the house, they are painted so that they do not rust.
In simple words: Painting iron surfaces isolates them from air and moisture, which are necessary for the rusting process.

🎯 Exam Tip: Recognize that this question is essentially a repeat of Question 2, reinforcing the same concept.

Use Your Brain Power!

 

Question 1. Can we permanently prevent the rusting of an iron article by applying a layer of paint on its surface?
Answer: The method of painting is alright for some time. We cannot protect the articles permanently from rusting by painting them.
In simple words: Painting offers temporary protection, as the paint layer can wear off or get damaged over time, exposing the metal to corrosion.

🎯 Exam Tip: Differentiate between temporary and permanent corrosion prevention methods; painting is considered temporary.

 

Question 2. Why do new iron sheets appear shiny?
Answer: The new iron sheets appear shiny because a layer of non-corrosionable metal is fixed on the surface of corrosionable metal.
In simple words: New iron sheets often have a protective, non-corrosive metallic coating, like zinc (galvanization), that gives them a shiny appearance.

🎯 Exam Tip: Understand that the "shiny" appearance often indicates a protective coating, such as galvanization, which prevents immediate corrosion.

Collect Information.

 

Question 1. What are the various alloys used in daily life? Where are those used?
Answer:

Various alloys	Uses
1. Bronze	It is used to prepare: Coins, utensils, medals, statues
2. Brass	Pipes, condenser tubes, utensils worshipping God.
3. Stainless steel	Utensils, tools, dairy equipment, boilers.
4. Steel	Construction of bridges and buildings, cutting tools, blades.
5. Tungsten steel	High speed cutting tools
6. Amalgam	Silver amalgam used by dentists
7. Duralumin	Bodies of aircraft, buses, kitchenwares
8. Aluminium bronze	Pigment in ink and paint
9. German silver	Electrical heaters, resistors
10. Gun metal	Guns, boiler fittings
11. Magnelium	Beams of scientific balances, aircraft parts.
12. Gold with copper or nickel or silver or platinum	Jewellery

In simple words: Alloys are mixtures of metals (or metals and nonmetals) created to achieve enhanced properties for specific applications, ranging from coins and tools to aircraft parts and jewelry.

🎯 Exam Tip: Memorizing common alloys and their primary uses is crucial for application-based questions.

 

Question 2. What are the properties that the alloy used for minting coins should have?
Answer: The alloy used for minting coins should have excellent wear resistance and anti-corrosion properties.
In simple words: Coin alloys need to be durable against wear from handling and resistant to corrosion to maintain their integrity and appearance over time.

🎯 Exam Tip: Consider practical applications when thinking about material properties; for coins, durability and corrosion resistance are key.

Fill In The Blanks:

 

Question 1. ...............has the highest melting point.
Answer: Tungsten has the highest melting point.
In simple words: Tungsten is known for its extremely high melting point, making it suitable for applications requiring heat resistance.

🎯 Exam Tip: Remember specific examples of elements with extreme properties, like tungsten's high melting point.

 

Question 2. Mercury and............are two metals in the liquid state at room temperature.
Answer: Mercury and galium are two metals in the liquid state at room temperature.
In simple words: Mercury and gallium are unique metals because they are liquid at or near room temperature.

🎯 Exam Tip: Know the exceptions to general rules, such as metals that are liquid at room temperature.

 

Question 3. ............is the hardest natural substance.
Answer: Diamond is the hardest natural substance.
In simple words: Diamond, an allotrope of carbon, holds the record as the hardest known natural material.

🎯 Exam Tip: Recall diamond's exceptional hardness as a key property of nonmetals.

 

Question 4. The naturally occurring compounds of metals along with other impurities are known as..
Answer: The naturally occurring compounds of metals along with other impurities are known as minerals.
In simple words: Minerals are the naturally occurring forms of metals, often found mixed with various impurities in the Earth's crust.

🎯 Exam Tip: Understand that minerals are the raw forms of metals found in nature, containing other substances.

 

Question 5. The minerals from which metals are extracted profitably and conveniently are called.
Answer: The minerals from which metals are extracted profitably and conveniently are called ores.
In simple words: Ores are specific minerals from which a metal can be economically and easily extracted.

🎯 Exam Tip: Differentiate between minerals (general natural compounds) and ores (economically viable sources of metal).

 

Question 6. An ore contains some of the impurities like soil, sand, etc. These impurities are called............
Answer: An ore contains some of the impurities like soil, sand, etc. These impurities are called gangue.
In simple words: Gangue refers to the unwanted earthy or rocky impurities found alongside the desired mineral in an ore.

🎯 Exam Tip: Recognize gangue as the non-valuable material that needs to be removed from an ore during extraction.

 

Question 7. The process of extraction of a metal from its ore is called..........
Answer: The process of extraction of a metal from its ore is called metallurgy.
In simple words: Metallurgy is the entire science and technology involved in extracting metals from their ores and refining them for use.

🎯 Exam Tip: Define metallurgy as the overarching process of metal extraction and purification.

 

Question 8. Bauxite is a common ore of...........
Answer: Bauxite is a common ore of aluminium.
In simple words: Bauxite is the primary and most important ore from which aluminum metal is extracted.

🎯 Exam Tip: Associate bauxite as the main ore for aluminum extraction.

 

Question 9. ........... process is used for the purification of bauxite.
Answer: Bayer's process is used for the purification of bauxite.
In simple words: Bayer's process is a chemical method specifically designed to purify bauxite ore before aluminum can be extracted.

🎯 Exam Tip: Remember Bayer's process as the key method for purifying bauxite ore.

 

Question 10. During the electrolysis of alumina, ...........is liberated at the anode.
Answer: During the electrolysis of alumina, oxygen is liberated at the anode.
In simple words: In the electrolytic reduction of alumina, oxygen gas is produced at the anode as aluminum ions are reduced at the cathode.

🎯 Exam Tip: Know the products liberated at the anode and cathode during the electrolysis of alumina.

 

Question 11. The reaction of iron oxide with aluminium is known as..............reaction.
Answer: The reaction of iron oxide with aluminium is known as thermit reaction.
In simple words: The thermit reaction is a highly exothermic process where aluminum reduces iron oxide, often used in welding.

🎯 Exam Tip: Identify the thermit reaction as a powerful reduction process involving aluminum and iron oxide, known for producing intense heat.

 

Question 12. The process of coating a thin layer of zinc on iron is known as............
Answer: The process of coating a thin layer of zinc on iron is known as galvanising.
In simple words: Galvanizing applies a protective zinc layer to iron or steel to prevent rusting through cathodic protection.

🎯 Exam Tip: Understand galvanizing as a common method for protecting iron from corrosion using zinc.

 

Question 13. The metal that produces a sound on striking a hard surface is said to be.............
Answer: The metal that produces a sound on striking a hard surface is said to be sonorous.
In simple words: Sonorous materials, typically metals, produce a ringing sound when struck, a property exploited in bells.

🎯 Exam Tip: Define sonorous as the property of metals to produce a characteristic sound when hit.

 

Question 14. ........... has an oxide which is soluble in sodium hydroxide.
(a) Calcium
(b) Magnesium
(c) Iron
(d) Zinc.
Answer: (d) Zinc
In simple words: Zinc oxide is amphoteric, meaning it reacts with strong bases like sodium hydroxide to form a soluble complex.

🎯 Exam Tip: Recognize that amphoteric oxides, such as zinc oxide, are soluble in both acids and strong bases.

 

Question 15. ........... prevents the rusting of iron.
(a) Copper
(b) Zinc
(c) Aluminium
(d) Silver
Answer: (b) Zinc
In simple words: Zinc prevents iron from rusting through galvanization, acting as a sacrificial anode because it is more reactive than iron.

🎯 Exam Tip: Galvanization, which uses zinc, is a key method for protecting iron from rust, leveraging zinc's higher reactivity.

 

Question 16. ........... is obtained by the reduction of its oxide by carbon.
(a) Zinc
(b) Aluminium
(c) Sodium
(d) Potassium
Answer: (a) Zinc
In simple words: Zinc is commonly extracted from its oxide by reduction with carbon, a process suitable for moderately reactive metals.

🎯 Exam Tip: Carbon reduction is effective for extracting moderately reactive metals like zinc from their oxides.

 

Question 17. ........... is used as an anode during the electrolytic reduction of bauxite.
(a) Sulphur
(b) Graphite
(c) Platinum
(d) Aluminium
Answer: (b) Graphite
In simple words: Graphite, a form of carbon, is used as the anode in the Hall-Héroult process for aluminum extraction because it conducts electricity and reacts with oxygen produced during electrolysis.

🎯 Exam Tip: Understand the role of graphite anodes in aluminum electrolysis, including their gradual consumption due to reaction with oxygen.

 

Question 18. Silver gets corroded due to ............ in air.
(a) oxygen
(b) hydrogen sulphide
(c) carbon dioxide
(d) nitrogen
Answer: (b) hydrogen sulphide
In simple words: Silver tarnishes and turns black when exposed to hydrogen sulphide in the air, forming silver sulphide.

🎯 Exam Tip: Know that silver's tarnish is caused by its reaction with sulfur compounds in the atmosphere, not oxygen directly.

 

Question 19. ........... is the hardest substance and has the highest melting and boiling points.
(a) Iodine
(b) Sulphur
(c) Diamond
(d) Phosphorus
Answer: (c) Diamond
In simple words: Diamond is an allotrope of carbon, renowned for being the hardest natural substance with exceptionally high melting and boiling points.

🎯 Exam Tip: Diamond's extreme hardness and high melting point are due to its strong covalent network structure.

 

Question 20. Jewellery articles are gold plated ...........
(a) to prevent corrosion
(b) to prevent rusting of the base metal
(c) to make articles attractive
(d) all of these
Answer: (d) all of these
In simple words: Gold plating serves multiple purposes: it protects the underlying metal from corrosion and rust, and significantly enhances the aesthetic appeal of the jewelry.

🎯 Exam Tip: Gold plating offers both protective and decorative benefits, making "all of these" the comprehensive answer.

 

Question 21. To show that zinc is more reactive than copper, the correct procedure is to ...........
(a) prepare copper sulphate solution and dip a zinc strip in it
(b) prepare zinc sulphate solution and dip a copper strip in it
(c) heat together zinc and copper strips
(d) add dil. nitric acid to both the strips
Answer: (a) prepare copper sulphate solution and dip a zinc strip in it
In simple words: To demonstrate zinc's higher reactivity, dipping a zinc strip into copper sulphate solution will cause zinc to displace copper, indicating a more reactive metal.

🎯 Exam Tip: A displacement reaction is a direct way to compare reactivity: a more reactive metal will displace a less reactive metal from its salt solution.

 

Question 22. Iron is ...........
(a) more reactive than zinc
(b) more reactive than aluminium
(c) less reactive than copper
(d) less reactive than aluminium
Answer: (d) less reactive than aluminium
In simple words: In the reactivity series, iron is placed below aluminum but above copper and zinc, meaning it is less reactive than aluminum.

🎯 Exam Tip: Accurately recalling the reactivity series of common metals is fundamental for comparing their chemical behavior.

 

Question 23. A solution of Al2(SO4)3 in water is ...........
(a) blue
(b) pink
(c) green
(d) colourless
Answer: (d) colourless
In simple words: Aluminum sulphate forms a colourless solution in water because aluminum ions do not absorb visible light and thus do not impart any colour.

🎯 Exam Tip: Many metal salts form colourless solutions if the metal ion does not have d-block electrons capable of visible light absorption.

 

Question 24. A solution of ............ in water is blue in colour.
(a) CuSO4
(b) FeSO4
(c) ZnSO4
(d) Al2(SO4)3
Answer: (a) CuSO4
In simple words: Copper sulphate (CuSO4) solution is famously blue due to the presence of hydrated copper(II) ions.

🎯 Exam Tip: Associate the blue color of solutions with copper(II) ions, a common observation in chemistry experiments.

 

Question 25. A solution of ............ in water is green in colour.
(a) CuSO4
(b) FeSO4
(c) ZnSO4
(d) Al2(SO4)3
Answer: (b) FeSO4
In simple words: Ferrous sulphate (FeSO4) solution typically has a light green color due to the presence of hydrated iron(II) ions.

🎯 Exam Tip: Remember that iron(II) compounds often form green solutions, while iron(III) compounds tend to be yellowish-brown.

 

Question 26. What would be the correct order if Zn, Fe, Al and Cu are arranged in increasing order of reactivity?
(a) Cu, Fe, Zn, Al
(b) Al, Cu, Fe, Zn
(c) Zn, Al, Cu, Fe
(d) Fe, Zn, Al, Cu
Answer: (a) Cu, Fe, Zn, Al
In simple words: The reactivity series places copper as the least reactive, followed by iron, then zinc, and finally aluminum as the most reactive among these four metals.

🎯 Exam Tip: Accurately recalling the reactivity series is essential for answering questions about displacement reactions and metal extraction methods.

 

Question 27. During the extraction of aluminium ...........
(a) Ingredients and gangue in bauxite
(b) Use of leaching during the concentration of ore
(c) Chemical reaction of transformation of bauxite into alumina by Hall's process.
(d) Heating the aluminium ore with concentrated caustic soda.
Answer: (c) Chemical reaction of transformation of bauxite into alumina by Hall's process.
In simple words: A key step in aluminum extraction involves chemically converting bauxite ore into pure alumina, often using the Hall's process for efficiency.

🎯 Exam Tip: Focus on the specific chemical reactions and industrial processes involved in the extraction of important metals like aluminum.

 

Question 28. A solution of CuSO4 in water is ............ in colour.
(a) pink
(b) blue
(c) colourless
(d) green
Answer: (b) blue
In simple words: Copper sulphate in water creates a distinct blue solution, a common characteristic of hydrated copper(II) ions.

🎯 Exam Tip: Visually associating specific metal ion solutions with their colors, such as copper sulphate with blue, helps in quick recall for MCQs.

 

Question 29. Which of the following process is to be carried out to avoid the formation of greenish layer on brass vessels due to corrosion?
(a) Plating
(b) Anodization
(c) Tinning
(d) Alloying
Answer: (c) Tinning
In simple words: Tinning coats brass vessels with a layer of tin, preventing the formation of the greenish copper carbonate layer caused by corrosion.

🎯 Exam Tip: Tinning is a practical corrosion prevention method for brass and copper vessels, especially for culinary use, to avoid toxic copper compounds.

State Whether The Following Statements Are True Or False (If A Statement Is False, Correct It And Rewrite It.):

 

Question 1. Metals are known as sonar metals.
Answer: True.
In simple words: Metals exhibit sonorousness, meaning they produce a ringing sound when struck, which is why they are sometimes called sonar metals.

🎯 Exam Tip: Connect the term "sonar metals" to the property of sonority, which is characteristic of most metals.

 

Question 2. Diamond is the softest natural substance.
Answer: False. (Diamond is the hardest natural substance.)
In simple words: Diamond is actually the hardest natural substance known, not the softest.

🎯 Exam Tip: Remember diamond's exceptional hardness as a key physical property, often tested in contrast to its other allotropes or common materials.

 

Question 3. Electrolysis method is used to obtain pure metals from impure metals.
Answer: True.
In simple words: Electrolytic refining is a widely used and effective method for purifying crude metals to obtain very high purity metals.

🎯 Exam Tip: Electrolysis is a crucial industrial process for metal refining, especially for highly pure metals.

 

Question 4. Iodine and diamond are lustrous substances.
Answer: True.
In simple words: While most nonmetals lack lustre, iodine and diamond are exceptions, possessing a shiny appearance.

🎯 Exam Tip: Remember iodine and diamond as exceptions to the general rule that nonmetals are non-lustrous.

 

Question 5. Aqua Regia is a mixture of conc. HCl and conc. HNO3 in the ratio of 1:3.
Answer: False. (Aqua Regia is a mixture of conc. HCl and conc. HNO3 in the ratio of 3:1.)
In simple words: Aqua Regia is a potent corrosive mixture of concentrated hydrochloric acid and nitric acid, specifically in a 3:1 ratio of HCl to HNO3.

🎯 Exam Tip: Crucially, recall the correct 3:1 ratio of HCl to HNO3 for aqua regia, as this is a common point of confusion.

 

Question 6. Corrosion of metals can be stopped by detaching the air from metals.
Answer: True.
In simple words: Preventing contact between a metal and atmospheric air, which contains oxygen and moisture, effectively halts the corrosion process.

🎯 Exam Tip: Understand that removing either oxygen or moisture, or both, from the metal's environment is key to preventing corrosion.

 

Question 7. Due to corrosion a greenish layer forms on the surface of copper or brass vessel.
Answer: True.
In simple words: Copper and brass corrode to form a protective greenish layer, primarily copper carbonate, when exposed to moist air.

🎯 Exam Tip: This greenish layer, often called patina, is a common sign of copper corrosion and actually helps protect the underlying metal.

 

Question 8. Ionic compounds are soluble in kerosene.
Answer: False. (Ionic compounds are soluble in water and insoluble in kerosene.)
In simple words: Ionic compounds are typically soluble in polar solvents like water but not in non-polar organic solvents such as kerosene.

🎯 Exam Tip: Remember the "like dissolves like" principle: ionic compounds (polar) dissolve in polar solvents, while non-polar substances dissolve in non-polar solvents.

 

Question 9. Ionic compounds in the solid state conduct electricity.
Answer: False. (Ionic compounds in the solid state do not conduct electricity.)
In simple words: In the solid state, ions in an ionic compound are held in fixed positions and cannot move freely, thus preventing electrical conduction.

🎯 Exam Tip: Ionic compounds conduct electricity only when molten or dissolved in water, as their ions become mobile.

 

Question 10. Mercury, silver and gold are very reactive metals.
Answer: False. (Mercury, silver and gold are least reactive metals.)
In simple words: Mercury, silver, and gold are noble metals, meaning they are relatively unreactive and are found in their free state in nature.

🎯 Exam Tip: Classify noble metals like gold and silver as least reactive due to their stability and resistance to corrosion.

 

Question 11. In electroplating a metal is coated with another metal using electrolysis.
Answer: True.
In simple words: Electroplating uses an electric current to deposit a thin layer of one metal onto the surface of another, enhancing properties like corrosion resistance or appearance.

🎯 Exam Tip: Electroplating is an electrochemical process where a thin metal coating is applied using an electric current, improving surface characteristics.

Question 2.Tinning : Tin :: Galvanizing :...............

Answer:Tinning : Tin :: Galvanizing : Zinc
In simple words: Tinning applies a layer of tin, while galvanizing applies a layer of zinc.

🎯 Exam Tip: Understanding analogies in metallurgy helps to distinguish between similar protective coating methods and their applications.

Question 3.Pressure cooker : Anodizing :: Silver plated spoons :...............

Answer:Pressure cooker : Anodizing :: Silver plated spoons : Electro-plating
In simple words: Anodizing is used for pressure cookers, and electroplating is used for silver-plated spoons.

🎯 Exam Tip: Focus on linking the specific metal protection technique with its common application to score well.

Question 4.The sulphides ores are strongly heated in air : Roasting :: The carbonates ores are strongly heated in a limited supply of air :...............

Answer:The sulphides ores are strongly heated in air : Roasting :: The carbonates ores are strongly heated in a limited supply of air : Calcination.
In simple words: Heating sulphide ores in air is roasting, while heating carbonate ores in limited air is calcination.

🎯 Exam Tip: Remember the key difference between roasting (excess air) and calcination (limited air) for sulphide and carbonate ores, respectively.

Question 5.Sulphide ores: Froth floatation method : Cassiterite ore :...............

Answer:Sulphide ores: Froth floatation method : Cassiterite ore : Magnetic separation method.
In simple words: Froth floatation is used for sulphide ores, and magnetic separation is used for cassiterite ore due to its magnetic properties.

🎯 Exam Tip: Associate each ore type with its appropriate concentration method (e.g., sulphide ores with froth floatation, magnetic ores with magnetic separation).

Find The Odd One Out:

Question 1.Sodium, Potassium, Silver, Sulphur

Answer:Sulphur. (All except sulphur, others are metals.)
In simple words: Sulphur is the odd one out because it is a nonmetal, while sodium, potassium, and silver are metals.

🎯 Exam Tip: Classify elements based on their fundamental properties (metal/nonmetal) to identify the odd one out correctly.

Question 2.Boron, Chlorine, Bromine, Fluorine

Answer:Boron. (All except boron, others are nonmetals.)
In simple words: Boron is the odd one out because it is a metalloid, whereas chlorine, bromine, and fluorine are nonmetals (halogens).

🎯 Exam Tip: Differentiate between metalloids and nonmetals to make accurate distinctions in chemical classification.

Question 3.Copper, Iron, Mercury, Brass

Answer:Brass. (All except brass, others are metals.)
In simple words: Brass is an alloy, while copper, iron, and mercury are pure metals.

🎯 Exam Tip: Remember that alloys are mixtures of metals (or metals and nonmetals), not pure elements.

Question 4.Brass, Bronze, Phosphorus, Stainless steel

Answer:Phosphorus. (All except phosphorus, others are alloys.)
In simple words: Phosphorus is an element (nonmetal), while brass, bronze, and stainless steel are alloys.

🎯 Exam Tip: Be able to identify common alloys and distinguish them from pure elements.

Question 5.Magnesium chloride, Sodium chloride, Water, Zinc chloride

Answer:Water. (All except water, others are ionic compounds.)
In simple words: Water is a covalent compound, while magnesium chloride, sodium chloride, and zinc chloride are ionic compounds.

🎯 Exam Tip: Classify compounds based on their bonding (ionic vs. covalent) to correctly identify the odd one out.

Question 6.Tinning, Anodization, Alloying, Froth floatation (March 2019)

Answer:Froth floatation. (All except froth floatation, others are processes of coating a thin layer of metal on the surface of other metals.)
In simple words: Froth floatation is an ore concentration method, while tinning, anodization, and alloying are methods for preventing metal corrosion or modifying metal properties.

🎯 Exam Tip: Understand the different applications of metallurgical processes: some are for ore beneficiation (like froth floatation), others for surface protection or property modification (like tinning, anodization, alloying).

Match The Following:

Question 1.

Column I	Column II
(1) ZnS	(a) Cuprous sulphide
(2) HgS	(b) Bauxite
(3) Cu2S	(c) Zinc blend
(4) Al2O3.H2O	(d) Cinnabar
	(e) Cryolite

Answer:(1) ZnS - Zinc blend
(2) HgS - Cinnabar
(3) Cu2S - Cuprous sulphide
(4) Al2O3.H2O - Bauxite.
In simple words: This matches common ores with their chemical formulas or names: ZnS is zinc blend, HgS is cinnabar, Cu2S is cuprous sulphide, and Al2O3.H2O is bauxite.

🎯 Exam Tip: Memorize the common names and chemical formulas of important metal ores.

Question 2.

Column I	Column II
(1) Copper and zinc	(a) Stainless steel
(2) Copper and tin	(b) Zinc amalgam
(3) Iron, nickel and chromium	(c) Bronze
(4) Mercury and zinc	(d) Brass
	(e) Steel

Answer:(1) Copper and zinc - Brass
(2) Copper and tin - Bronze
(3) Iron, nickel and chromium - Stainless steel
(4) Mercury and zinc - Zinc amalgam.
In simple words: This matches alloys with their constituent metals: Brass is copper and zinc, Bronze is copper and tin, Stainless steel is iron, nickel and chromium, and Zinc amalgam is mercury and zinc.

🎯 Exam Tip: Learn the compositions of common alloys as they are frequently tested.

Question 3.

Column I	Column II
(1) Galvanising	(a) Pressure cooker
(2) Tinning	(b) Silver plated spoons
(3) Electroplating	(c) Coating of tin on copper
(4) Anodizing	(d) Coating of Zn on iron

Answer:(1) Galvanising - Coating of Zn on iron
(2) Tinning - Coating of tin on copper
(3) Electroplating - Silver plated spoons
(4) Anodizing - Pressure cooker.
In simple words: This matches metal protection methods with their applications or defining characteristics: Galvanizing coats iron with zinc, Tinning coats copper with tin, Electroplating makes silver-plated spoons, and Anodizing is used for items like pressure cookers.

🎯 Exam Tip: Distinguish between various corrosion prevention methods by knowing their specific coatings and typical applications.

Translate The Following Statements Into Chemical Equations And Then Balance Them:

Question 1.steam is passed over aluminium.

Answer:\[2Al_{(s)} + 3H_2O_{(g)} \rightarrow Al_2O_{3(s)} + 3H_{2(g)}\]In simple words: When aluminum reacts with steam, it forms aluminum oxide and hydrogen gas.

🎯 Exam Tip: For reactions involving steam, remember that metals like aluminum form oxides and release hydrogen gas.

Question 2.Extraction of copper from its sulphide ore.

Answer:\[2Cu_2S_{(s)} + 3O_{2(g)} \xrightarrow{\text{heat}} 2Cu_2O_{(s)} + 2SO_{2(g)}\]
\[2Cu_2O_{(s)} + Cu_2S_{(s)} \xrightarrow{\text{heat}} 6Cu_{(s)} + SO_{2(g)}\]In simple words: Copper sulphide ore is first roasted to form copper oxide, which then reacts with remaining copper sulphide to yield pure copper.

🎯 Exam Tip: Note that copper extraction from sulphide ores involves two main steps: roasting to oxide, followed by self-reduction.

Question 3.Thermit reaction.

Answer:\[3Fe_3O_2 + 4Al \rightarrow 9Fe + 2Al_2O_3 + \text{heat}\]In simple words: The thermit reaction involves aluminum reducing iron oxide to elemental iron, releasing a large amount of heat.

🎯 Exam Tip: The thermit reaction is highly exothermic and is used in welding, demonstrating aluminum's strong reducing power.

Question 4.Magnesium reacts with hot water.

Answer:\[Mg_{(s)} + 2H_2O_{(l)} \rightarrow Mg(OH)_{2(aq)} + H_{2(g)}\]In simple words: Magnesium reacts with hot water to produce magnesium hydroxide and hydrogen gas.

🎯 Exam Tip: Be aware that magnesium reacts with hot water, not cold water, to form its hydroxide and hydrogen.

Question 5.what happens when aluminium oxide dissolves in aqueous sodium hydroxide?

Answer:\[Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 + H_2O\]In simple words: Aluminum oxide, being amphoteric, reacts with sodium hydroxide to form soluble sodium aluminate and water.

🎯 Exam Tip: Remember that amphoteric oxides like aluminum oxide react with both acids and strong bases.

Question 6.Zinc reacts with sulphuric acid.

Answer:\[Zn_{(s)} + H_2SO_{4(aq)} \rightarrow ZnSO_{4(aq)} + H_2 \uparrow\]In simple words: Zinc reacts with sulphuric acid to produce zinc sulphate and hydrogen gas.

🎯 Exam Tip: Most reactive metals (above hydrogen in the reactivity series) react with dilute acids to produce hydrogen gas and a salt.

Question 7.Iron reacts with sulphuric acid.

Answer:\[Fe_{(s)} + H_2SO_4 \rightarrow FeSO_{4(aq)} + H_2 \uparrow\]In simple words: Iron reacts with sulphuric acid to form ferrous sulphate and hydrogen gas.

🎯 Exam Tip: Similar to zinc, iron also displaces hydrogen from dilute acids because it is more reactive than hydrogen.

Name The Following:

Question 1.A metal which forms an amphoteric oxide.

Answer:Aluminium forms an amphoteric oxide.
In simple words: Aluminum is a metal that forms an oxide which can react as both an acid and a base.

🎯 Exam Tip: Identify key examples of amphoteric oxides, such as aluminum oxide and zinc oxide.

Question 2.An alloy of copper and zinc.

Answer:An alloy of copper and zinc is termed as brass.
In simple words: Brass is an alloy made by combining copper and zinc.

🎯 Exam Tip: Know the common alloys and their constituent elements, like brass (copper and zinc) and bronze (copper and tin).

Question 3.A compound which is added to lower the fusion temperature.

Answer:Cryolite (AlF3, 3NaF) and fluorspar (CaF2) are added to lower the fusion temperature.
In simple words: Cryolite and fluorspar are compounds used to reduce the melting point in industrial processes, such as aluminum extraction.

🎯 Exam Tip: Remember the role of cryolite and fluorspar as fluxes in the electrolytic reduction of alumina to lower the melting point and improve conductivity.

Question 4.A metal which does not react with cold water but reacts with steam.

Answer:Aluminium does not react With cold water but reacts with Steam.
In simple words: Aluminum is a metal that is unreactive with cold water but will react with high-temperature steam.

🎯 Exam Tip: Metals' reactivity with water varies; some react with cold water, some with hot water, and others only with steam.

Question 5.A common ore of aluminium.

Answer:Bauxite (Al2O3.H2O) is a common ore of aluminium.
In simple words: Bauxite, which is hydrated aluminum oxide, is the primary source from which aluminum is extracted.

🎯 Exam Tip: Bauxite is the most important ore for aluminum, and its chemical formula is useful to remember.

Question 6.A metal which is in liquid state at ordinary temperature.

Answer:Mercury is in liquid state at ordinary temperature.
In simple words: Mercury is a unique metal that exists as a liquid at room temperature.

🎯 Exam Tip: Mercury is an important exception to the general rule that metals are solid at room temperature.

Question 7.Two metals which are malleable.

Answer:Iron and aluminium are malleable metals.
In simple words: Iron and aluminum can be hammered or rolled into thin sheets without breaking.

🎯 Exam Tip: Malleability is a key physical property of most metals, allowing them to be shaped.

Question 8.Two metals which are ductile.

Answer:Gold and silver are ductile metals.
In simple words: Gold and silver can be drawn into thin wires.

🎯 Exam Tip: Ductility is another characteristic property of metals, allowing them to be drawn into wires.

Question 9.Two metals which are good conductors of heat.

Answer:Silver and copper are good conductors of heat.
In simple words: Silver and copper efficiently transfer thermal energy.

🎯 Exam Tip: Excellent thermal conductivity is a common property of metals due to free electrons.

Question 10.Two metals which are good conductors of electricity.

Answer:Copper and aluminium are good conductors of electricity.
In simple words: Copper and aluminum readily allow electric current to pass through them.

🎯 Exam Tip: High electrical conductivity is a defining characteristic of metals, vital for electrical wiring.

Question 11.Two metals which are used for making cooking vessels.

Answer:Copper and aluminium are used in making cooking vessels.
In simple words: Copper and aluminum are commonly used for cooking pots because they conduct heat well.

🎯 Exam Tip: The good thermal conductivity of copper and aluminum makes them suitable for cooking utensils.

Question 12.Two metals having low melting points.

Answer:Sodium and potassium have low melting points.
In simple words: Sodium and potassium are soft alkali metals with unusually low melting points compared to other metals.

🎯 Exam Tip: Remember that alkali metals (like sodium and potassium) are exceptions to the general rule of high melting points for metals.

Question 13.Two highly reactive metals.

Answer:Sodium and potassium are highly reactive metals.
In simple words: Sodium and potassium are very reactive and readily undergo chemical reactions.

🎯 Exam Tip: Alkali metals (Group 1) are known for being among the most reactive metals due to having a single valence electron.

Question 14.A nonmetal which is in liquid state at room temperature.

Answer:Bromine is in liquid state at room temperature.
In simple words: Bromine is the only nonmetal that exists as a liquid at normal room temperature.

🎯 Exam Tip: Bromine is an important exception to the general rule that nonmetals are either gases or solids at room temperature.

Question 15.Two ionic compounds.

Answer:Sodium chloride (NaCl) and magnesium chloride (MgCl2) are ionic compounds.
In simple words: Sodium chloride and magnesium chloride are examples of compounds formed by the electrostatic attraction between oppositely charged ions.

🎯 Exam Tip: Ionic compounds typically form between a metal and a nonmetal, involving the transfer of electrons.

Question 16.The process of heating the sulphide ore to a high temperature in the excess of air.

Answer:In roasting, sulphide ore is heated to a high temperature in the excess of air.
In simple words: Roasting is a metallurgical process where sulphide ores are heated in abundant air to convert them into oxides.

🎯 Exam Tip: Distinguish roasting from calcination by remembering that roasting requires excess air for sulphide ores.

Question 17.The process of heating the carbonate ore to a high temperature in limited air.

Answer:In calcination, carbonated ore is heated to a high temperature in limited air.
In simple words: Calcination is a process where carbonate ores are heated without much air to decompose them into oxides.

🎯 Exam Tip: Remember that calcination specifically targets carbonate ores and is carried out in limited air.

Question 18.The compound formed by the reaction between aluminium oxide and sodium hydroxide.

Answer:Sodium aluminate is formed by the reaction between aluminium oxide and sodium hydroxide.
In simple words: When aluminum oxide reacts with sodium hydroxide, it forms sodium aluminate.

🎯 Exam Tip: This reaction highlights the amphoteric nature of aluminum oxide, reacting with a strong base.

Question 19.Two metals which are found in the free state in nature.

Answer:Gold (Au) and silver (Ag) are found in the free state in nature.
In simple words: Gold and silver are unreactive metals that can be found as pure elements in nature.

🎯 Exam Tip: Unreactive metals like gold and silver often occur in their native (free) state due to their low chemical reactivity.

Question 20.A metal which has the highest melting point.

Answer:Tungsten has the highest melting point.
In simple words: Tungsten is a metal known for its exceptionally high melting point.

🎯 Exam Tip: Tungsten's high melting point makes it suitable for applications like light bulb filaments.

Question 21.Two nonmetals which are lustrous.

Answer:Iodine and diamond are lustrous in nature.
In simple words: Iodine and diamond are nonmetals that, unlike most nonmetals, possess a shiny appearance.

🎯 Exam Tip: Remember these exceptions to the general property that nonmetals lack lustre.

Answer The Following Questions In One Sentence Each:

Question 1.State the property of the metals due to which they can be drawn into wires.

Answer:The property of the metal due to which they can be drawn into wires is called ductility.
In simple words: Ductility is the property that allows metals to be pulled into thin wires.

🎯 Exam Tip: Clearly define ductility and its application (wire drawing) when asked about this metal property.

Question 2.State the property of the metals due to which they can be beaten into thin sheets.

Answer:The property of the metals due to which they can be beaten into thin sheets is called malleability.
In simple words: Malleability is the property that allows metals to be flattened into thin sheets.

🎯 Exam Tip: Clearly define malleability and its application (sheet formation) when asked about this metal property.

Question 3.Which is the hardest substance?

Answer:Diamond which is a form of carbon is the hardest substance.
In simple words: Diamond, an allotrope of carbon, is known to be the hardest natural substance.

🎯 Exam Tip: Diamond's exceptional hardness is an important physical property to recall.

Question 4.What material is used to coat electrical wires?

Answer:PVC (Polyvinyl chloride) is used to coat electrical wires.
In simple words: Polyvinyl chloride (PVC) is a common insulating material used to cover electrical wires.

🎯 Exam Tip: PVC is used as an insulator due to its non-conductivity and flexibility, making it ideal for wire coatings.

Question 5.State two metals which can be cut easily with a knife.

Answer:Sodium and potassium are soft metals and can be cut easily with a knife.
In simple words: Sodium and potassium are alkali metals soft enough to be cut with a knife.

🎯 Exam Tip: Sodium and potassium are important exceptions to the general hardness of metals.

Question 6.Which of the following metals react with cold water?
Sodium, iron, copper, potassium.

Answer:Sodium and potassium metals react with cold water.
In simple words: Sodium and potassium are highly reactive metals that readily react with cold water.

🎯 Exam Tip: Metals like sodium and potassium are highly reactive and react vigorously with cold water, producing hydrogen gas.

Question 7.Which of the following metals do not react with cold water or hot water?
Sodium, potassium, aluminium, iron.

Answer:Aluminium and iron do not react with cold water or hot water.
In simple words: Aluminum and iron are less reactive than sodium and potassium and do not react with cold or hot water.

🎯 Exam Tip: Understand the reactivity series to predict how different metals will react with water at various temperatures.

Question 8.State two metals which displace hydrogen from dilute acids and two metals which do not do so.

Answer:Metals which displace hydrogen from dilute acids are: Magnesium and zinc.
Metals which do not displace hydrogen from dilute acids are: Copper and silver.
In simple words: Magnesium and zinc are more reactive than hydrogen and can displace it from acids, while copper and silver are less reactive and cannot.

🎯 Exam Tip: Metals above hydrogen in the reactivity series displace hydrogen from dilute acids; those below hydrogen do not.

Question 9.Arrange the following metals in the increasing order of their activity:
Copper, Silver, Aluminium, Iron. (Practice Activity Sheet - 1)

Answer:The arrangement of metals in the increasing order of their activity:
Silver < Copper < Iron < Aluminium
In simple words: In order of increasing reactivity, the metals are silver, then copper, followed by iron, and finally aluminum.

🎯 Exam Tip: Knowing the reactivity series is crucial for arranging metals by their activity and predicting reaction outcomes.

Question 10.Write the chemical equation for the reaction of hot iron with steam.

Answer:\[3Fe_{(s)} + 4H_2O_{(g)} \rightarrow Fe_3O_{4(s)} + 4H_{2(g)}\]In simple words: When hot iron reacts with steam, it produces iron (III) oxide and hydrogen gas.

🎯 Exam Tip: Remember that iron reacts with steam (not just hot water) to form a mixed oxide (Fe3O4) and hydrogen.

Question 11.Complete the following reactions:
(1) Zn(s) + H2O(g) →
(2) C(s) + O2(g) Combustion →

Answer:(1) \(Zn_{(s)} + H_2O_{(g)} \rightarrow ZnO_{(s)} + H_{2(g)}\)
(2) \(C_{(s)} + O_{2(g)} \xrightarrow{\text{Combustion}} CO_{2(g)} \text{ (acidic oxide)}\)
In simple words: Zinc reacts with steam to form zinc oxide and hydrogen, while carbon burns in oxygen to form carbon dioxide, an acidic oxide.

🎯 Exam Tip: Pay attention to the conditions (e.g., steam vs. liquid water, combustion) when writing chemical equations to ensure correct products.

Question 12.Complete the following reactions:
(1) N2(g) + 3H2(g) Proper temp.
high pressure →
(2) 2C(s) + O2(g) Partial combustion →

Answer:(1) \(N_{2(g)} + 3H_{2(g)} \xrightarrow{\text{Proper temp., high pressure}} 2NH_{3(g)}\) (Ammonia)
(2) \(2C_{(s)} + O_{2(g)} \xrightarrow{\text{Partial combustion}} 2CO_{(g)}\) (Neutral) (Carbon monoxide)
In simple words: Nitrogen and hydrogen react under specific conditions to form ammonia, while partial combustion of carbon forms carbon monoxide.

🎯 Exam Tip: For synthesis reactions, remember specific conditions like temperature and pressure, and for combustion, note if it's complete or partial.

Question 13.3MnO2 + 4Al → 3Mn + 2Al2O3 + heat.
Identify the substances undergone oxidation and reduction reactions.

Answer:MnO2 is reduced to Mn.
Al is oxidised to Al2O3
In simple words: In this reaction, manganese dioxide loses oxygen (reduced) to become manganese, while aluminum gains oxygen (oxidized) to become aluminum oxide.

🎯 Exam Tip: Use the "OIL RIG" mnemonic (Oxidation Is Loss, Reduction Is Gain of oxygen/hydrogen, or electrons) to identify oxidized and reduced species.

Question 14.State the impurities present in the bauxite ore.

Answer:The main impurities present in the bauxite ore are silica (SiO2) and iron oxide (Fe2O3).
In simple words: Bauxite, the aluminum ore, commonly contains silica and iron oxide as impurities.

🎯 Exam Tip: Knowing the common impurities in ores is important for understanding their concentration methods.

Question 15.Write the formula of (i) bauxite (ii) cryolite.

Answer:The formula of bauxite is Al2O3.H2O and that of cryolite is (Na3AlF6).
In simple words: Bauxite is hydrated aluminum oxide, and cryolite is sodium hexafluoroaluminate.

🎯 Exam Tip: Memorize the chemical formulas of key ores and compounds involved in metallurgy, such as bauxite and cryolite.

Question 16.What is galvanization?

Answer:The process of coating a thin layer of zinc on iron or steel is called galvanization.
In simple words: Galvanization is applying a protective zinc coating to iron or steel to prevent rusting.

🎯 Exam Tip: Galvanization is a common and effective method to protect iron from corrosion by cathodic protection.

Question 17.Name the reaction in which aluminium is used as a reducing agent.

Answer:The thermite reaction in which iron oxide is reduced by aluminium. Aluminium is used as a reducing agent in the thermit reaction.
In simple words: The thermite reaction uses aluminum as a powerful reducing agent to extract metals from their oxides, especially iron oxide.

🎯 Exam Tip: Aluminum's high reactivity makes it an excellent reducing agent in specific reactions like the thermite process.

Question 18.What are the constituents of bronze?

Answer:Copper and tin are the constituents of bronze.
In simple words: Bronze is an alloy primarily composed of copper and tin.

🎯 Exam Tip: Remember the main components of common alloys like bronze for identification and comparison.

Question 19.State the term used to express the purity of gold.

Answer:The purity of gold is expressed in carat.
In simple words: Gold's purity is measured in carats, with 24-carat being pure gold.

🎯 Exam Tip: Carat is a specific unit for gold purity, distinct from the carat unit for gemstone weight.

Question 20.What is meant by amalgam?

Answer:The amalgam is an alloy in which one of the metals is mercury.
In simple words: An amalgam is a special type of alloy where mercury is one of the component metals.

🎯 Exam Tip: Amalgams are important in dentistry (e.g., silver amalgam) due to mercury's ability to alloy with other metals.

Question 21.What is meant by electroplating?

Answer:A process in which a less reactive metal is coated on a more reactive metal by electrolysis is called electroplating.
In simple words: Electroplating uses an electric current to deposit a thin layer of one metal onto the surface of another, usually for protection or decoration.

🎯 Exam Tip: Understand that electroplating is an electrolytic process for surface coating, often using a less reactive metal on a more reactive one.

Question 22.Why are metals called electropositive elements?

Answer:Metals are reactive. They lose electrons and become positively charged ions. Therefore, metals are called electropositive elements.
In simple words: Metals are called electropositive because they tend to lose electrons easily to form positive ions.

🎯 Exam Tip: The electropositive nature of metals is directly linked to their tendency to donate electrons in chemical reactions.

Answer The Following Questions:

Question 1.Distinguish between the physical properties of metals and nonmetals with respect to the following points:
(1) Physical state (2) Lustre (3) Ductility and malleability (4) Conduction of heat and electricity (5) Hardness (6) Melting and boiling points.

Answer:(1) Physical state: Under ordinary conditions, metals are generally solids. Exceptions: mercury and gallium are liquids. Under ordinary conditions, nonmetals may be solids or gases. Exception: bromine is in liquid state.
(2) Lustre: Metals usually have a high lustre (called metallic lustre). They can be polished to give a highly reflective surface. With the exceptions of gold and copper, metals usually have silvery grey colour. Nonmetals lack lustre, exceptions: graphite and iodine. Some nonmetals are colourless and others possess a variety of colours.
(3) Ductility and malleability: Metals are ductile and malleable. Nonmetals are not ductile and mallfeable.
(4) Conduction of heat and electricity: Metals are good conductors of heat and electricity. Nonmetals are bad conductors of heat and electricity. Exception: Graphite is a good conductor of electricity.
(5) Hardness: Metals are usually hard, but not brittle, exceptions: sodium, potassium, lead, zinc. Nonmetals are brittle in the solid state, exception: diamond.
(6) Melting and boiling points: The melting and boiling points of metals are high, exceptions: sodium, potassium, mercury, gallium. The melting and boiling points of nonmetals are low, exceptions: carbon, silicon.
In simple words: Metals are typically solid, lustrous, malleable, ductile, and good conductors with high melting points, while nonmetals are usually gases or brittle solids, lack lustre, are not malleable or ductile, are poor conductors, and have low melting points, both categories having some exceptions.

🎯 Exam Tip: When distinguishing between metals and nonmetals, focus on providing contrasting points for each property, including notable exceptions.

Question 2.Write any three physical properties of nonmetals.

Answer:1. Nonmetals may be solid or gaseous.
2. Nonmetals lack lustre. They are not ductile and malleable.
3. The melting and boiling points of nonmetals are low.
4. Nonmetals are bad conductors of heat and electricity.
In simple words: Nonmetals can be solid or gas, lack shine, are not easily shaped into wires or sheets, and generally have low melting points and poor conductivity.

🎯 Exam Tip: When listing properties, choose distinct characteristics (e.g., state, lustre, conductivity) to provide a comprehensive answer.

Question 3.Metals are good conductors of heat. Explain why.

Answer:(1) The electrons in the outermost shells of atoms of a metal are free to move throughout the metal.
(2) When a metal is heated, these electrons start moving with higher velocity and conduct heat. Hence, metals are good conductors of heat.
In simple words: Metals are good heat conductors because they have free, mobile electrons that rapidly transfer thermal energy throughout the material when heated.

🎯 Exam Tip: The presence of delocalized electrons is key to explaining both thermal and electrical conductivity in metals.

Question 4.Metals are good conductors of electricity. Explain why.

Answer:(1) The electrons in the outermost shells of atoms of a metal are free to move throughout the metal.
(2) When a potential difference is applied between the ends of a metal wire, the net movement of the electrons in a particular direction, from a point at lower potential to a point at higher potential, constitutes an electric current. Hence, metals are good conductors of electricity.
In simple words: Metals conduct electricity well because their free electrons can move easily when an electric potential is applied, creating an electric current.

🎯 Exam Tip: Connect the mobility of free electrons directly to the flow of charge (electric current) to explain electrical conductivity.

Question 5.A metal can be drawn into a wire. Explain why.

Answer:1. The property due to which a substance can be drawn into a thin wire without cracking or breaking is called ductility.
2. Metals are ductile. Thus, a metal can be drawn into a wire.
In simple words: Metals can be drawn into wires because they possess ductility, a property that allows them to be stretched without breaking.

🎯 Exam Tip: Define ductility accurately and state that metals exhibit this property due to their atomic structure, allowing layers of atoms to slide past each other.

Question 6.A metal can be hammered into a thin sheet. Explain why.

Answer:1. The property due to which a substance can be hammered (or rolled) into a thin sheet without cracking is called malleability.
2. Metals are malleable. Thus, a metal can be hammered to form a thin sheet.
In simple words: Metals can be hammered into thin sheets because they are malleable, meaning they can be deformed under compression without fracturing.

🎯 Exam Tip: Define malleability and explain that the ability of metal atoms to slide past each other without breaking metallic bonds contributes to this property.

2. Nonmetals lack lustre. They are not ductile and malleable.
3. The melting and boiling points of nonmetals are low.
4. Nonmetals are bad conductors of heat and electricity.
In simple words: Nonmetals generally lack shine, cannot be drawn into wires or hammered into sheets, have low melting/boiling points, and do not conduct heat or electricity well.

🎯 Exam Tip: Remember key exceptions like graphite (conducts electricity) and diamond (hardest substance, good conductor of heat) for nonmetal properties.

 

Question 3. Metals are good conductors of heat. Explain why.
Answer:
(1) The electrons in the outermost shells of atoms of a metal are free to move throughout the metal.
(2) When a metal is heated, these electrons start moving with higher velocity and conduct heat. Hence, metals are good conductors of heat.
In simple words: Metals conduct heat well because they have free-moving electrons that can transfer thermal energy quickly when heated.

🎯 Exam Tip: The concept of "free electrons" is crucial for explaining both heat and electrical conductivity in metals.

 

Question 4. Metals are good conductors of electricity. Explain why.
Answer:
(1) The electrons in the outermost shells of atoms of a metal are free to move throughout the metal.
(2) When a potential difference is applied between the ends of a metal wire, the net movement of the electrons in a particular direction, from a point at lower potential to a point at higher potential, constitutes an electric current. Hence, metals are good conductors of electricity.
In simple words: Metals conduct electricity because their outermost electrons are free to move. When voltage is applied, these electrons flow, creating an electric current.

🎯 Exam Tip: Electrical conductivity is a direct consequence of the delocalized electron sea model in metals.

 

Question 5. A metal can be drawn into a wire. Explain why.
Answer:
1. The property due to which a substance can be drawn into a thin wire without cracking or breaking is called ductility.
2. Metals are ductile. Thus, a metal can be drawn into a wire.
In simple words: Metals can be pulled into thin wires because they possess the property of ductility, allowing them to stretch without breaking.

🎯 Exam Tip: Ductility is a key physical property of metals, important for applications like electrical wiring.

 

Question 6. A metal can be hammered into a thin sheet. Explain why.
Answer:
1. The property due to which a substance can be hammered (or rolled) into a thin sheet without cracking is called malleability.
2. Metals are malleable. Thus, a metal can be hammered to form a thin sheet.
In simple words: Metals can be flattened into thin sheets because they are malleable, meaning they can be hammered or rolled without cracking.

🎯 Exam Tip: Malleability is another essential physical property of metals, enabling their use in various structural and decorative forms.

 

Question 7. How do metals react with oxygen?
Answer: Metals combine with oxygen on heating in air and metal oxides are formed.
Metal + Oxygen
\( \implies \) Metal oxide
2Na(s) +O\(_2\)(g)
\( \implies \) Na\(_2\)O(s)
Sodium oxide
2Mg(s) +O\(_2\)(g)
\( \implies \) 2MgO(s)
Magnesium oxide
In simple words: Metals react with oxygen, often upon heating, to form metal oxides, such as sodium forming sodium oxide or magnesium forming magnesium oxide.

🎯 Exam Tip: Pay attention to the stoichiometry and state symbols in the chemical equations for metal-oxygen reactions.

 

Question 8. How does a metal react with water?
Answer: Sodium and potassium react vigorously with water to evolve hydrogen. Calcium reacts with water slowly and less vigorously to evolve hydrogen and the metal floats on water. Magnesium reacts with hot water to evolve hydrogen. Aluminium, iron and zinc do not react with cold or hot water but they react with steam to evolve their oxides and hydrogen.
2Na(s) + 2H\(_2\)O(l)
\( \implies \) 2NaOH(aq) + H\(_2\)(g) + heat energy
2K(s) + 2H\(_2\)O(l)
\( \implies \) 2KOH(aq) + H\(_2\)(g) + heat energy
2Ca(s) + 2H\(_2\)O(l)
\( \implies \) 2Ca(OH)\(_2\)(aq) + H\(_2\)(g)
Mg(s) + 2H\(_2\)O(hot)
\( \implies \) Mg(OH)\(_2\)(aq) + H\(_2\)(g)
2Al(s) + 3H\(_2\)O steam
\( \implies \) Al\(_2\)O\(_3\)(s) + 3H\(_2\)(g)
3Fe(s) + 4H\(_2\)O steam
\( \implies \) Fe\(_3\)O\(_4\) + 4H\(_2\)(g)
Zn(s) + H\(_2\)O steam
\( \implies \) ZnO(s) + H\(_2\)(g)
In simple words: Metals react with water to different extents; highly reactive metals like sodium and potassium react vigorously, while others like magnesium react with hot water, and some like aluminium, iron, and zinc react only with steam.

🎯 Exam Tip: Note the different conditions (cold water, hot water, steam) required for various metals to react with water, reflecting their reactivity differences.

 

Question 9. How does a metal react with an acid?
Answer: Reaction of metals with acids: Metals react with dilute hydrochloric acid or dilute sulphuric acid to form metal chloride or metal sulphate and hydrogen gas. The rate of evolution of H\(_2\) is maximum in case of magnesium. The reactivity decreases in the
order
Mg > Al > Zn > Fe.
Mg(s) + 2HCl(aq)
\( \implies \) MgCl\(_2\)(s) + H\(_2\)(g)
2Al(s) + 6HCl(aq)
\( \implies \) 2AlCl\(_3\)(aq) + 3H\(_2\)(g)
Zn(s) + 2HCl(aq)
\( \implies \) ZnCl\(_2\)(aq) + H\(_2\)(g)
Fe(s) + 2HCl(aq)
\( \implies \) FeCl\(_2\)(aq) + H\(_2\)(g)
Fe(s) + H\(_2\)SO\(_4\)(aq)
\( \implies \) FeSO\(_4\) + H\(_2\)(g)
Zn(s) + H\(_2\)SO\(_4\)(aq)
\( \implies \) ZnSO\(_4\) + H\(_2\)(g)
Mg(s) + H\(_2\)SO\(_4\)(aq)
\( \implies \) MgSO\(_4\)(aq) + H\(_2\)(g)
In simple words: Metals react with dilute acids to produce a metal salt and hydrogen gas, with more reactive metals showing a faster reaction rate.

🎯 Exam Tip: The reactivity series of metals can predict whether a metal will displace hydrogen from a dilute acid.

 

Question 10. How does a metal react with nitric acid?
Answer: Metals react with nitric acid to form nitrate salts. Depending on the concentration of nitric acid, various oxides of nitrogen (NO, NO\(_2\)) are formed.
Cu(s) + 4HNO\(_3\)
\( \implies \) Cu(NO\(_3\))\(_2\)(aq) + 2NO\(_2\)(g) + 2H\(_2\)O(l)
(Conc.)
Cu(s) + 8HNO\(_3\)
\( \implies \) 3Cu(NO\(_3\))\(_2\)(aq) + 2NO(g) + 4H\(_2\)O(l)
(dilute)
In simple words: Metals react with nitric acid to form metal nitrates and various nitrogen oxides, with the specific oxide depending on the acid's concentration.

🎯 Exam Tip: Nitric acid is a strong oxidizing agent, so it typically produces nitrogen oxides instead of hydrogen gas when reacting with metals.

 

Question 11. Arrange the following metals in the decreasing order of chemical reactivity: Cu, Mg, Fe, Ca, Zn, Na.
Answer: The reactivity of metal decreases in the following order:
Na > Mg > Ca > Zn > Fe > Cu.
In simple words: The metals arranged from most reactive to least reactive are Sodium, Magnesium, Calcium, Zinc, Iron, and Copper.

🎯 Exam Tip: Understanding the reactivity series is fundamental for predicting the outcomes of displacement reactions and the stability of metal compounds.

 

Question 12. What is meant by aqua regia?
Answer: Aqua regia is a highly corrosive and fuming liquid. It is a freshly prepared mixture of conc. HCl and conc. HNO\(_3\) in the ratio of 3:1. Most of the substances dissolve in it. Aqua regia is a reagent which dissolves gold and platinum.
In simple words: Aqua regia is a potent, fuming acid mixture of concentrated hydrochloric acid and nitric acid (3:1 ratio) capable of dissolving noble metals like gold and platinum.

🎯 Exam Tip: Aqua regia's unique ability to dissolve noble metals makes it significant in chemistry, especially in the recovery and purification of these elements.

 

Question 13. How does a metal react with salts of other metals?
Answer: The reaction of metals with solutions of salts of other metals is the displacement reaction. If a metal A displaces other metal B from the solution of its salt, it means that the metal A is more reactive than the metal B.
Metal A + Salt solution of metal B
\( \implies \) Salt solution of metal A + metal B
Fe + CuSO\(_4\)
\( \implies \) FeSO\(_4\) + Cu
Iron Copper sulphate
In this reaction Fe has displaced Cu from CuSO\(_4\). It means Fe is more reactive than Cu.
In simple words: A more reactive metal can displace a less reactive metal from its salt solution, forming a new salt and releasing the less reactive metal.

🎯 Exam Tip: Displacement reactions are governed by the reactivity series; a metal higher in the series will displace a metal lower in the series.

 

Question 14. Explain the reactivity series of the metals.
Answer: The arrangement of metals in decreasing order of their reactivity in the form of a series is called the reactivity or activity series of the metals. The most reactive metal is placed at the top of the list and least reactive metal is placed at the bottom of the list.
On the basis of reactivity, we can classify metals into the following categories:
1. High reactivity metals
2. Moderately reactive metals
3. Less reactive metals.
1. Extraction of High reactivity metals: The metals which are placed at the top of the reactivity series are very reactive. They are never found in nature as free elements, e.g., sodium, potassium, calcium and aluminium. These metals are obtained by electrolytic reduction.
2. Extraction of Moderately reactive metals: The metals in the middle of reactivity series such as iron, zinc, lead, copper are moderately reactive. These elements are present as sulphides or carbonates in nature. Generally metals are obtained from their oxide as compared to their sulphides and carbonates.
3. Extraction of Less reactive metals: The metals which are placed at the bottom of the reactivity series are least reactive. They occur in free state, e.g. gold, silver and copper.
In simple words: The reactivity series is a list of metals arranged in decreasing order of their chemical reactivity, used to classify them for extraction methods and predict reaction outcomes.

🎯 Exam Tip: The reactivity series is crucial for understanding the principles of metallurgy and predicting the feasibility of different extraction processes for metals.

 

Question 15. Atomic number of metal "A" is 11, while atomic number of metal “B” is 20. Which of them will be more reactive? Identify these metals. Write the chemical reaction of dilute HCl with metal "A".
Answer: Metal 'A' is more reactive than metal 'B'.
Atomic number of metal 'A' is 11, hence it is Na.
2Na + 2HCl
\( \implies \) 2NaCl(aq) + H\(_2\)(g)
In simple words: Metal A (Sodium) is more reactive than metal B (Calcium) because it has fewer outermost electrons to lose. Sodium reacts with dilute HCl to form sodium chloride and hydrogen gas.

🎯 Exam Tip: Reactivity of metals is often inversely proportional to the number of valence electrons, as losing fewer electrons is energetically more favorable.

 

Question 16. How does a metal react with a nonmetal?
Answer: By oxidation of a metal, cations are formed, on the other hand by reduction of a nonmetal, anions are formed. The ionic compound is formed due to the metal losing electrons while the nonmetal accepts the electrons. The ionic compound of sodium chloride is formed as sodium loses one electron while chlorine accepts one electron.
Na
\( \implies \) Na\(^+\) + e-
Cl+e
\( \implies \) Cl-
Na + Cl
\( \implies \) NaCl
Sodium chloride
Similarly Mg and K form ionic compounds MgCl\(_2\) and KCl.
In simple words: Metals react with nonmetals by transferring electrons to form ionic compounds, where the metal becomes a positive ion (cation) and the nonmetal becomes a negative ion (anion).

🎯 Exam Tip: The formation of ionic bonds through electron transfer is a fundamental concept for understanding metal-nonmetal reactions.

 

Question 17. How do nonmetals react with oxygen?
Answer: Nonmetals combine with oxygen to form acidic oxides. In some cases, neutral oxides
are formed.
Complete Combustion
C(s) + O\(_2\)(g)
\( \implies \) CO\(_2\)(g) (Acidic)
Carbon dioxide
Combustion
S(s) + O\(_2\)(g)
\( \implies \) SO\(_2\)(g) (Acidic)
Sulphur dioxide
Partial Combustion
2C(s) + O\(_2\)(g)
\( \implies \) 2CO (Neutral)
Carbon monoxide
In simple words: Nonmetals react with oxygen to form either acidic oxides (like CO\(_2\) or SO\(_2\)) or, in some specific cases, neutral oxides (like CO), depending on conditions.

🎯 Exam Tip: Remember that metal oxides are typically basic, while nonmetal oxides are generally acidic or neutral, which helps distinguish their chemical behavior.

 

Question 18. How do nonmetals react with water?
Answer: Nonmetals do not react with water, (exception : halogen). Chlorine dissolves in water giving hypochlorous acid.
Cl\(_2\)(g) + H\(_2\)O(l)
\( \implies \) HOCl(aq) + HCl(aq)
Hypochlorous acid
In simple words: Generally, nonmetals do not react with water, though halogens like chlorine are an exception, dissolving to form acids.

🎯 Exam Tip: Note the distinction between dissolving and reacting; some nonmetals dissolve without undergoing a chemical reaction with water.

 

Question 19. How do nonmetals react with dilute acids?
Answer: Nonmetals do not react with dilute acid, (exception: halogen). Chlorine reacts with dil. hydrobromic acid to form bromine and HCl.
Cl\(_2\)(g) + 2HBr(aq)
\( \implies \) 2HCl(aq) + Br\(_2\)(aq)
Bromine
In simple words: Nonmetals typically do not react with dilute acids, except for halogens which can participate in displacement reactions.

🎯 Exam Tip: Remember that nonmetals are generally less reactive than hydrogen with acids, which is why they don't displace hydrogen.

 

Question 20. How do nonmetals react with hydrogen?
Answer: Nonmetals react with hydrogen under certain conditions (such as proper temperature, pressure, catalyst, etc.)
N\(_2\)(g) + 3H\(_2\)(g)
\( \implies \) 2NH\(_3\)
Nitrogen
Ammonia
S + H\(_2\)(g)
\( \implies \) H\(_2\)S
Sulphur
Hydrogen sulphide
In simple words: Nonmetals react with hydrogen under specific conditions (temperature, pressure, catalyst) to form hydrides, like ammonia from nitrogen or hydrogen sulfide from sulfur.

🎯 Exam Tip: These reactions often require specific industrial conditions, emphasizing the role of catalysts and controlled environments in chemical synthesis.

 

Question 21. What is meant by an ionic compound?
Answer: The compound formed from two units, namely cation and anion is called an ionic compound.
In simple words: An ionic compound is a chemical substance formed when positively charged ions (cations) and negatively charged ions (anions) bond together through electrostatic attraction.

🎯 Exam Tip: Ionic compounds typically form between a metal (which forms cations) and a nonmetal (which forms anions).

 

Question 22. What is meant by an ionic bond?
Answer: The cation and anion being oppositely charged, there is an electrostatic force of attraction between them, this force of attraction between cation and anion is called the ionic bond.
In simple words: An ionic bond is the strong electrostatic force of attraction that holds together oppositely charged ions (cations and anions) in an ionic compound.

🎯 Exam Tip: Ionic bonds result from the complete transfer of electrons from one atom to another, leading to stable octet configurations.

 

Question 23. State the general properties of ionic compounds.
Answer:
1. Ionic compounds are solids and hard due to strong electrostatic force of attraction between oppositely charged ions.
2. They are generally brittle. When pressure is applied they break into pieces.
3. They have high melting and boiling points, due to intermolecular force of attraction is high in ionic compounds.
4. They are soluble in water and insoluble in solvents such as kerosene and petrol.
5. Ionic compounds cannot conduct electricity when in solid state, they are electrically neutral. They conduct electricity in the molten state and also in an aqueous solution.
In simple words: Ionic compounds are typically hard, brittle solids with high melting/boiling points, soluble in water but not organic solvents, and conduct electricity only when molten or in solution.

🎯 Exam Tip: The strong electrostatic forces between ions are responsible for most of the characteristic physical properties of ionic compounds.

 

Question 24. Explain the following terms:
1. Concentration of ores
2. Roasting
3. Calcination
4. Refining
Answer:
1. Concentration of ores: The process of separating gangue from the other ores is called concentration of ores.
2. Roasting: The process of heating an ore to a high temperature in excess of air and converting it into its oxide is called roasting. Examples: ZnS (zinc blend), PbS (Galena)
ZnS O\(_2\) (heat)
\( \implies \) ZnO
oxidation
3. Calcination: The process of heating an ore in a limited supply of air and converting it into its oxide is called calcination. Example: Zinc carbonate (ZnCO\(_3\))
ZnCO\(_3\)
\( \implies \) ZnO + CO\(_2\) \( \uparrow \)
4. Refining: The metal obtained by chemical reduction contains impurities. The process of electrolysis method is used to obtain pure metals from impure metals is known as refining.
In simple words: Concentration removes impurities from ore, roasting heats sulfide ores in air to form oxides, calcination heats carbonate ores in limited air to form oxides, and refining purifies crude metals, often by electrolysis.

🎯 Exam Tip: Clearly distinguishing between roasting (excess air) and calcination (limited air) is important for accurately describing ore concentration methods.

 

Question 25. State two methods of concentration of ores in which the heavy particles of ores can be separated from the light gangue particles by the gravitational method.
Answer:
1. Wilfley table method
2. Hydraulic separation method are two methods of concentration of ores in which the heavy particles of ores can be separated from the light, gangue particles by the gravitational method.
In simple words: The Wilfley table and hydraulic separation are two gravity-based methods used to separate heavier ore particles from lighter gangue.

🎯 Exam Tip: Gravitational separation methods are effective when there's a significant density difference between the ore and the gangue.

 

Question 26. What are the different methods used for removing gangue from ores? (OR) Write the five methods of concentration of ores.
Answer:
1. Wilfley table method
2. Hydraulic separation method
3. Magnetic separation method
4. Froth floatation method
5. Leaching method.
In simple words: Methods for removing gangue include Wilfley table, hydraulic, magnetic, froth floatation, and leaching, each suitable for different ore properties.

🎯 Exam Tip: Each concentration method exploits different physical or chemical properties of the ore and gangue, making the choice dependent on the specific mineral.

 

Question 27. Write short notes on:
(1) Wilfley table method
(2) Hydraulic separation method
(3) Magnetic separation method
(4) Froth floatation method
(5) Leaching method.
Answer:
(1) Wilfley table method : (Separation based on gravitation) This method of separation uses the Wilfley table, it is made by fixing narrow and thin wooden wedges/blocks on inclined surface with low slope. The table is kept continuously vibrating.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र विल्फली टेबल विधि को दर्शाता है। इसमें एक झुकी हुई, कंपन करने वाली मेज पर लकड़ी के पतले ब्लॉक लगे होते हैं। पाउडर किए गए अयस्क को मेज पर डाला जाता है, और पानी की एक धारा इसे धो देती है। हल्के गैंग के कण पानी के साथ बह जाते हैं, जबकि भारी अयस्क के कण लकड़ी के वेजेज में फंस जाते हैं और नीचे जमा हो जाते हैं।
Lumps of the ore is made powdered ore by using ball mill. This powdered ore is poured on the table and a stream of water is simultaneously released from the upper side. This result in the lighter gangue particles getting carried away along with the flowing water, while the heavier particles in which proportion of minerals is more and proportion of gangue particles is less, are blocked by the wooden wedges and is collected through the slits between them.
(2) Hydraulic separation method: The hydraulic separation method is based on the working of a mill. This is a tapering vessel similar to that used in a grinding mill. It opens in a tank like a container that is tapering on the lower side. The tank has an outlet for water on the upper side and a water inlet on the lower side.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र हाइड्रोलिक पृथक्करण विधि को दर्शाता है। इसमें एक पतला होता हुआ (टैपरिंग) बर्तन होता है जहाँ ऊपर से पाउडर अयस्क डाला जाता है। नीचे से पानी की एक तेज धारा डाली जाती है। हल्के गैंग के कण पानी के साथ ऊपर के आउटलेट से बाहर निकल जाते हैं, जबकि भारी अयस्क के कण बर्तन के निचले हिस्से में जमा हो जाते हैं।
Finely ground ore is added to the tank. A fast stream of water is released in the tank from the lower side. The lighter gangue particles flow out along with the water stream from the outlet on the upper side of the tank and are collected separately, simultaneously the heavy particles of the ore are collected at the bottom from the lower side of the tank. This method is based on the law of gravitation, wherein particles of the same size are separated by their weight with the help of water.
(3) Magnetic separation method: Electro-magnetic machine is used in this method. The main parts of this machine are two types of iron rollers and the conveyor belt continuously moving around them. One of the rollers is nonmagnetic while the other is electromagnetic. The conveyor belt moving around the rollers is made up of leather or brass (nonmagnetic). The powdered ore is poured at that end of the conveyor belt which is on the side of the nonmagnetic roller. Two collector vessels are placed below the magnetic roller.
The particles of the nonmagnetic part in the ore are not attracted towards the magnetic roller. Therefore, they are carried out further along the belt and fall in the collector vessel which is away from the magnetic roller. Simultaneously the particles of the magnetic ingredients of the ore stick to the magnetic roller and therefore fall in the collector vessel near the belt.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र चुंबकीय पृथक्करण विधि को दर्शाता है। इसमें एक कन्वेयर बेल्ट दो रोलर्स के चारों ओर घूमता है, जिसमें से एक चुंबकीय होता है। पाउडर अयस्क को गैर-चुंबकीय रोलर के ऊपर से बेल्ट पर गिराया जाता है। गैर-चुंबकीय कण बेल्ट से दूर गिरते हैं, जबकि चुंबकीय कण चुंबकीय रोलर के पास गिरते हैं, जिससे वे अलग हो जाते हैं।
In this way the magnetic and nonmagnetic particles in the ore are separated because of their magnetic nature. For example, cassiterite is a tin ore. It contains mainly the nonmagnetic ingredient stannic oxide (SnO\(_2\)) and the magnetic ingredient ferrous tungstate (FeWO\(_4\)). These are separated by the electromagnetic method.
(4) Froth floatation method: The froth floatation method is based on the two opposite properties, hydrophilic and hydrophobic, of the particles. The metal sulphides particles get wet mainly with oil due to their hydrophobic property. The gangue particles get wet with water due to the hydrophilic property.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र झाग प्लवन विधि को दर्शाता है। एक बड़े टैंक में पानी, पाउडर अयस्क और चीड़ का तेल मिलाया जाता है। हवा को मिश्रण में डाला जाता है जिससे झाग बनता है। अयस्क के कण तेल से गीले होकर झाग में तैरते हैं, जबकि गैंग के कण पानी से गीले होकर नीचे बैठ जाते हैं, जिससे अयस्क का सांद्रण होता है।
In this method the finely ground mineral is put into a big tank containing a lot of water. The finely powdered ore and vegetable oil such as pine oil, eucalyptus oil are mixed with water for formation of froth. The pressurised air is blown through the mixture. There is an agitator rotating around its axis in the centre of the floatation tank. The agitator is used as per the requirement. Bubbles are formed due to the blown air.
A foam is formed from oil, water and air bubbles together, due to the agitating. This foam rises to the surface of the water and floats. Hence this method is called froth floatation. Sulphide minerals float with the foam on water as they get and can be removed. The gangue particles are wetted by water, settles down at the bottom. This method is used for concentration of zinc blend (ZnS) and copper pyrite (CuFeS\(_2\)).
(5) Leaching: Leaching is the first step in the extraction of the metals like aluminium, gold and silver from their ores. In this method the ore is soaked in a particular solution for long time. The ore dissolves in that solution due to specific chemical reaction. The gangue, however, does not react and therefore does not dissolve in that solution. It can be separated easily.
For example, concentration of bauxite, the aluminium ore, is done by leaching method. Bauxite is soaked in aqueous NaOH or aqueous Na\(_2\)CO\(_3\) which dissolves the main ingredient alumina in it. This means that bauxite is leached by sodium hydroxide.
In simple words: These methods—Wilfley table, hydraulic, magnetic, froth flotation, and leaching—are diverse techniques used to concentrate ores by exploiting differences in density, magnetic properties, surface wettability, or chemical solubility between the ore and its impurities.

🎯 Exam Tip: For each method, clearly identify the principle of separation (e.g., gravity, magnetism, surface properties, chemical reaction) and provide a relevant example or application.

 

Question 28. Draw a neat labelled diagram of the arrangement of the equipment used in (1) Wilfley table method (2) Hydraulic separation method.
Answer:
1. Wilfley table method:

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र विल्फली टेबल विधि को दर्शाता है, जिसमें पाउडर किया हुआ अयस्क एक झुकी हुई, कंपन करने वाली मेज पर डाला जाता है जिसमें लकड़ी के ब्लॉक होते हैं। पानी की धारा हल्के गैंग को हटा देती है जबकि भारी अयस्क के कण मेज पर बने खांचों में फंसकर नीचे एकत्रित हो जाते हैं, जिससे उनका सांद्रण होता है।
2. Hydraulic separation method:

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र हाइड्रोलिक पृथक्करण विधि को दर्शाता है, जिसमें एक पतला होता हुआ बर्तन होता है। पाउडर अयस्क ऊपर से डाला जाता है, और पानी की एक तेज धारा नीचे से प्रवेश करती है। हल्के गैंग के कण पानी के साथ ऊपर के आउटलेट से बह जाते हैं, जबकि भारी अयस्क के कण नीचे जमा हो जाते हैं, जिससे अयस्क का सांद्रण होता है।
In simple words: This question requires drawing the labelled diagrams for the Wilfley table method and the Hydraulic separation method, illustrating their equipment setup and how they separate ore from gangue.

🎯 Exam Tip: For diagrams, ensure all parts are clearly labelled and the setup accurately reflects the method's working principle to score full marks.

 

Question 29. Complete the following flow chart and answer the questions below:
Answer:
Concentration of ores
Gravitation based separation
Magnetic Separation
Leaching
Froth floatation
(i) Pine oil is used in froth floatation method.
(ii) The finely powdered ore and vegetable oil such as pine oil, eucalyptus oil are mixed with water for formation of froth. The pressurised air is blown through the mixture. The agitator is used as per the requirement. Bubbles are formed due to the blown air. A foam is formed from oil, water and air bubbles together, due to the agitating. This foam rises to the surface of the water and floats. Hence this method is called froth floatation. Sulphide minerals float with the foam on water as they get and can be removed. The gangue particles are wetted by water, settles down at the bottom. This method is used for concentration of zinc blend (ZnS) and copper pyrite (CuFeS\(_2\)).
In simple words: The flow chart illustrates various ore concentration methods, where pine oil is used in froth flotation to separate sulfide ores by selective wetting and floating, while lighter impurities settle.

🎯 Exam Tip: Flow charts are excellent visual aids for understanding processes; be prepared to identify the methods and explain their underlying principles, especially for froth flotation.

 

Question 31.How are sodium, magnesium and potassium obtained from their molten chloride salts?
Answer:The metals sodium, calcium and magnesium are obtained by electrolysis of their molten chloride salts. In this process metal is deposited on the cathode while chlorine gas is liberated at the anode.
In simple words: Sodium, magnesium, and potassium are extracted from their molten chloride salts through electrolysis, where the metal deposits at the cathode and chlorine gas is released at the anode.

🎯 Exam Tip: Understanding the principle of electrolytic reduction is crucial for scoring well in questions related to metal extraction.

 

Question 32.Name the main ore of aluminium.
Answer:Bauxite \((\text{Al}_2\text{O}_3\cdot\text{H}_2\text{O})\) is the main ore of aluminium.
In simple words: The primary ore from which aluminum is obtained is Bauxite, a hydrated form of aluminum oxide.

🎯 Exam Tip: Remember the chemical formula and common name of important ores like Bauxite, as they are frequently tested.

 

Question 33.What is bauxite? What are the main impurities found in this ore?
Answer:Bauxite \((\text{Al}_2\text{O}_3 \cdot \text{H}_2\text{O})\) is hydrated aluminium oxide. It contains 30% to 70% \( \text{Al}_2\text{O}_3 \). The main impurities present in it are iron oxide \((\text{Fe}_2\text{O}_3)\) and sand \((\text{SiO}_2)\).
In simple words: Bauxite is a hydrated aluminum oxide mineral, rich in \( \text{Al}_2\text{O}_3 \), but it also commonly contains impurities like iron oxide and silica.

🎯 Exam Tip: Knowing both the composition and common impurities of major ores like bauxite helps in understanding the subsequent extraction processes.

 

Question 34.From which ore is aluminium extracted? What are the stages in its extraction (give only names)?
Answer:Aluminium is extracted from bauxite \((\text{Al}_2\text{O}_3\cdot\text{nH}_2\text{O})\). Stages id the extraction:
(i) Concentration of ore, i.e., conversion of bauxite into alumina,
(ii) Electrolytic reduction of alumina.
In simple words: Aluminum is extracted from bauxite through two main stages: concentrating the bauxite into alumina, and then electrolytically reducing the alumina to pure aluminum.

🎯 Exam Tip: Being able to list the key stages of metal extraction processes, especially for common metals like aluminum, is essential.

 

Question 35.Describe Bayer's process for concentration of bauxite.
Answer:(1) Bayer's process is used to obtain pure aluminium oxide from bauxite. (2) Bauxite is then concentrated by chemical separation. Bauxite contains impurities like iron oxide \((\text{Fe}_2\text{O}_3)\) and silica \((\text{SiO}_2)\). (3) Bauxite ore is powdered and heated with sodium hydroxide under high pressure for 2 to 8 hours at 140 °C in the digester. The aluminium oxide being amphoteric in nature present in bauxite reacts with sodium hydroxide to form water soluble sodium aluminate. This means that bauxite leached by sodium hydroxide. Silica reacts with sodium hydroxide to form soluble sodium silicate. The basic iron oxide \((\text{Fe}_2\text{O}_3)\) in the gangue remains unaffected. It is separated by filtration. \[ \text{Al}_2\text{O}_3(\text{s}) + 2\text{NaOH}(\text{aq}) \rightarrow 2\text{NaAlO}_2(\text{aq}) + \text{H}_2\text{O}(\text{l}) \] (From impure bauxite ore) (Sodium aluminate) \[ \text{SiO}_2 + 2\text{NaOH}(\text{aq}) \rightarrow \text{Na}_2\text{SiO}_3 + \text{H}_2\text{O} \] (silica) (Sodium silicate) (4) The filtrate containing sodium aluminate and sodium silicate is stirred with water and then cooling to 50° C. It is hydrolysed to give precipitate of aluminium hydroxide. \[ \text{NaAlO}_2(\text{aq}) + 2\text{H}_2\text{O}(\text{l}) \rightarrow \text{Al}(\text{OH})_3(\text{s}) \downarrow + \text{NaOH}(\text{aq}) \] (Aluminium hydroxide)
In simple words: Bayer's process purifies bauxite by reacting it with hot sodium hydroxide, forming soluble sodium aluminate while impurities like iron oxide are left behind. The sodium aluminate is then hydrolyzed to precipitate aluminum hydroxide, which can be further processed.

🎯 Exam Tip: Pay close attention to the amphoteric nature of aluminum oxide and the role of sodium hydroxide in selectively dissolving it during Bayer's process.

 

Question 36.Describe Hall's process for concentration of bauxite.
Answer:In Hall's process the ore is powdered and then it is leached by heating with aqueous sodium carbonate in the digester to form water soluble sodium aluminate. Then the insoluble impurities are filtered opt. The filtrate is warmed and neutralised by passing carbon dioxide gas through it. This result in precipitation of aluminium hydroxide. \[ \text{Al}_2\text{O}_3\cdot2\text{H}_2\text{O}(\text{s}) + \text{Na}_2\text{CO}_3(\text{aq}) \rightarrow 2\text{NaAlO}_2(\text{aq}) \] (Sodium aluminate) \[ \text{+CO}_2\uparrow+2\text{H}_2\text{O (l)} \] \[ 2\text{NaAlO}_2(\text{aq}) + 3\text{H}_2\text{O} + \text{CO}_2(\text{g}) \rightarrow 2\text{Al}(\text{OH})_3\downarrow + \text{Na}_2\text{CO}_3 \] (Aluminium hydroxide) The precipitate of \( \text{Al}(\text{OH})_3 \) obtained in this processes is filtered, washed, dried and then calcinated by heating at 1000 °C to obtain alumina. \[ 2\text{Al}(\text{OH})_3 \xrightarrow{1000 \text{ °C}} \text{Al}_2\text{O}_3 + 3\text{H}_2\text{O} \] (Alumina)
In simple words: Hall's process for bauxite concentration involves leaching with sodium carbonate to form soluble sodium aluminate, filtering out impurities, and then precipitating aluminum hydroxide by passing carbon dioxide, which is finally calcined to yield pure alumina.

🎯 Exam Tip: Note the key difference in reagents (sodium carbonate vs. sodium hydroxide) between Hall's and Bayer's processes for bauxite concentration.

 

Question 37.Describe the process of preparation of aluminium by the electrolysis of alumina. (OR) Draw and label the diagram of electrolysis of alumina and explain the electrolytic reduction of alumina.
Answer:Electrolytic reduction of alumina:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख एल्यूमिना के इलेक्ट्रोलिटिक अपचयन के लिए उपकरण को दर्शाता है। इसमें ग्रेफाइट से बनी एनोड छड़ें, ग्रेफाइट-लाइन वाली कैथोड, और पिघले हुए एल्यूमिना, क्रायोलाइट और फ्लूओर्सपार का मिश्रण एक स्टील टैंक में भरा होता है। पिघला हुआ एल्यूमीनियम टैंक के निचले हिस्से से बाहर निकलता है। (1) The electrolytic cell consists of a rectangular steel tank lined from inside with graphite. (2) The carbon lining (graphite) acts as a cathode. The anode consists of graphite rods suspended in the molten electrolyte. (3) Alumina has very high melting point (> 2000 °C). The electrolysis of alumina is carried out at a low temperature by dissolving it in molten cryolite \((\text{Na}_3\text{AlF}_6)\). The solution of alumina in cryolite and small amount of fluorspar \((\text{CaF}_2)\) is added in the mixture to lower its melting point up to 1000 °C. (4) On passing an electric current, alumina is electrolysed. (5) Molten aluminium is collected at the cathode, while oxygen gas is evolved at the anode. The electrode reactions are shown below: \[ \text{Al}_2\text{O}_3 \rightarrow 2\text{Al}^{3+} + 3\text{O}^{2-} \] Anode reaction: \( 2\text{O}^{2-} \rightarrow \text{O}_2(\text{g}) + 4\text{e}^- \) Cathode reaction: \( \text{Al}^{3+} + 3\text{e}^- \rightarrow \text{Al} \) The molten aluminium is heavier than the electrolyte. Therefore, it sinks to the bottom of the electrolyte and is removed from time to time. About 99% pure aluminium is obtained by this process. The oxygen gas liberated reacts with carbon anode and forms carbon dioxide. As the anode gets oxidised during the electrolysis of alumina, it has to be replaced from time to time.
In simple words: Aluminum is produced by electrolytically reducing alumina dissolved in molten cryolite, which lowers its melting point. Carbon anodes are used, and aluminum collects at the cathode while oxygen reacts with the anodes to form carbon dioxide.

🎯 Exam Tip: Understand the components of the electrolytic cell, the role of cryolite and fluorspar, and the specific electrode reactions to explain the process effectively.

 

Question 38.In the extraction of aluminium:
(i) Name the process of concentration of bauxite.
Answer:The process of concentration of bauxite is known as Bayer's process.
In simple words: The process used to concentrate bauxite, aluminum's ore, is called Bayer's process.

🎯 Exam Tip: Accurately naming key processes like Bayer's is fundamental for demonstrating knowledge.

 

(ii) Write the cathode reaction in electrolytic reduction of alumina.
Answer:At the cathode: \( \text{Al}^{3+} + 3\text{e}^- \rightarrow \text{Al} \).
In simple words: During the electrolytic reduction of alumina, aluminum ions gain three electrons at the cathode to form pure aluminum metal.

🎯 Exam Tip: Precisely writing the half-reactions at the electrodes is critical for chemistry questions involving electrolysis.

 

(iii) Write the function and formula of cryolite in the extraction of aluminium.
Answer:Cryolite is added to the molten mixture of alumina to reduce the melting point to about 1000 °C. The formula of cryolite is \( (\text{Na}_3\text{AlF}_6) \) or \( \text{AlF}_3, 3\text{NaF} \).
In simple words: Cryolite is used in aluminum extraction to lower alumina's melting point, making the electrolytic process more energy-efficient; its formula is \( \text{Na}_3\text{AlF}_6 \).

🎯 Exam Tip: Know the specific role and chemical formula of auxiliary substances like cryolite in industrial processes.

 

(iv) write an equation for the action of heat on aluminium hydroxide.
Answer:\[ 2\text{Al}(\text{OH})_3 \xrightarrow{\text{heat}} \text{Al}_2\text{O}_3 + 3\text{H}_2\text{O} \] (Aluminium hydroxide) (Alumina) (Water)
In simple words: When heated, aluminum hydroxide decomposes to form aluminum oxide and water.

🎯 Exam Tip: Always remember to balance chemical equations and indicate reaction conditions where appropriate.

 

(v) Draw the diagram of extraction of aluminium.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख एल्यूमिना के इलेक्ट्रोलिटिक अपचयन के लिए उपकरण को दर्शाता है। इसमें ग्रेफाइट से बनी एनोड छड़ें, ग्रेफाइट-लाइन वाली कैथोड, और पिघले हुए एल्यूमिना, क्रायोलाइट और फ्लूओर्सपार का मिश्रण एक स्टील टैंक में भरा होता है। पिघला हुआ एल्यूमीनियम टैंक के निचले हिस्से से बाहर निकलता है।
In simple words: (Diagram explanation provided above)

🎯 Exam Tip: Practice drawing and labeling diagrams of key experimental setups and industrial processes, as they often appear in exams.

 

(vi) Write the anode reaction in electrolytic reduction of alumina.
Answer:\[ \text{Al}_2\text{O}_3 \rightarrow 2\text{Al}^{3+} + 3\text{O}^{2-} \] At Anode: \( 2\text{O}^{2-} \rightarrow \text{O}_2(\text{g}) + 4\text{e}^- \)
In simple words: At the anode during alumina electrolysis, oxide ions lose electrons to form oxygen gas.

🎯 Exam Tip: Differentiate between anode (oxidation) and cathode (reduction) reactions in electrolysis.

 

(vii) Write the cathode reaction in electrolytic reduction of alumina.
Answer:\[ \text{Al}_2\text{O}_3 \rightarrow 2\text{Al}^{3+} + 3\text{O}^{2-} \] Cathode: \( \text{Al}^{3+} + 3\text{e}^- \rightarrow \text{Al}(\text{l}) \)
In simple words: At the cathode, aluminum ions gain electrons to become molten aluminum metal.

🎯 Exam Tip: Ensure consistency in specifying the state symbols (e.g., (l) for liquid) in chemical equations.

 

Question 39.What happens when aluminium ore is heated with caustic soda? Write the balanced chemical equation for the same.
Answer:When aluminium ore is heated with caustic soda solution under high pressure for 2 to 8 hours and at 140 °C to 150 °C, aluminium oxide from aluminium ore, being amphoteric in nature, dissolves in caustic soda solution to form sodium aluminate. \[ \text{Al}_2\text{O}_3 + 2\text{NaOH} \rightarrow 2\text{NaAlO}_2 + \text{H}_2\text{O} \] (aluminium oxide) (sodium hydroxide) (sodium aluminate)
In simple words: Heating aluminum ore with caustic soda causes the amphoteric aluminum oxide to dissolve, forming soluble sodium aluminate.

🎯 Exam Tip: Highlight the amphoteric nature of aluminum oxide as a key property that enables its dissolution in both acids and strong bases.

 

Question 40.How is zinc extracted from its ore zinc sulphide or zinc carbonate?
Answer:The crude zinc sulphide ore is heated strongly in excess of air. Zinc sulphide is converted into zinc oxide. This process is known as roasting. \[ 2\text{ZnS}(\text{s}) + 3\text{O}_2(\text{g}) \xrightarrow{\text{heat}} 2\text{ZnO}(\text{s}) + 2\text{SO}_2(\text{g}) \] (Zinc sulphide) (Oxygen) (Zinc oxide) (Sulphur dioxide) (OR) The crude zinc carbonate ore is heated strongly in limited supply of air. Zinc carbonate is converted into zinc oxide. This process is known as calcination. \[ \text{ZnCO}_3(\text{s}) \xrightarrow{\text{heat}} \text{ZnO}(\text{s}) + \text{CO}_2(\text{g}) \] (Zinc carbonate) (Zinc oxide) (Carbon dioxide) The zinc oxide is reduced to zinc by using a reducing agent such as carbon. \[ \text{ZnO}(\text{s}) + \text{C}(\text{s}) \rightarrow \text{Zn}(\text{s}) + \text{CO}(\text{g}) \] (Zinc oxide) (Carbon) (Zinc) (Carbon monoxide)
In simple words: Zinc is extracted from zinc sulphide by roasting to form zinc oxide, or from zinc carbonate by calcination to form zinc oxide. The zinc oxide is then reduced to zinc metal using carbon.

🎯 Exam Tip: Clearly distinguish between roasting (heating in excess air for sulphide ores) and calcination (heating in limited air for carbonate ores) and their respective products.

 

Question 41.How is copper extracted from its sulphide ore?
Answer:Copper is found as cuprous sulphide \((\text{Cu}_2\text{S})\) in nature. When \( \text{Cu}_2\text{S} \) is heated in air, copper is obtained. \[ 2\text{Cu}_2\text{S} + 3\text{O}_2 \xrightarrow{\text{heat}} 2\text{Cu}_2\text{O} + 2\text{SO}_2(\text{g})\uparrow \] (Cuprous sulphide) (Oxygen) (Cuprous oxide) (Sulphur dioxide) \[ 2\text{Cu}_2\text{O} + \text{Cu}_2\text{S} \xrightarrow{\text{heat}} 6\text{Cu}(\text{s}) + \text{SO}_2(\text{g})\uparrow \] (Cuprous oxide) (Cuprous sulphide) (Copper) (Sulphur dioxide)
In simple words: Copper is extracted from its sulphide ore, cuprous sulphide, by heating it in air to form cuprous oxide, which then reacts with remaining cuprous sulphide to produce molten copper and sulfur dioxide.

🎯 Exam Tip: Remember that copper extraction from its sulphide ore involves both oxidation (roasting) and subsequent self-reduction steps.

 

Question 42.How is mercury extracted from cinnabar? (OR) Extraction of mercury from its ore cinnabar and write the corresponding chemical reaction.
Answer:Cinnabar is an ore of mercury. When cinnabar is heated (roasted), it is converted into mercuric oxide \((\text{HgO})\). Mercuric oxide is then reduced to mercury on further heating. \[ 2\text{HgS}(\text{s}) + 3\text{O}_2(\text{g}) \xrightarrow{\text{heat}} 2\text{HgO}(\text{s}) + 2\text{SO}_2(\text{g}) \] (Cinnabar) \[ 2\text{HgO}(\text{s}) \xrightarrow{\text{heat}} 2\text{Hg} + \text{O}_2(\text{g}) \] (Mercuric oxide) (Mercury) (Oxygen)
In simple words: Mercury is extracted from its ore, cinnabar, by first roasting the cinnabar to form mercuric oxide, which is then further heated to decompose into pure mercury and oxygen.

🎯 Exam Tip: For metals with low reactivity, direct thermal decomposition of their oxides (like mercuric oxide) is a common extraction method.

 

Question 43.Show the steps involved in the extraction of moderately reactive metals from their sulphide ores.
Answer:Moderately reactive elements are present as sulphides or carbonates in nature.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख सल्फाइड अयस्कों से मध्यम रूप से प्रतिक्रियाशील धातुओं के निष्कर्षण में शामिल चरणों को दर्शाता है। सल्फाइड अयस्क को पहले हवा की अधिकता में उच्च तापमान पर गर्म किया जाता है (रोस्टिंग), जिससे धातु ऑक्साइड बनता है। फिर धातु ऑक्साइड को अपचयन (reduction) प्रक्रिया द्वारा धातु में बदला जाता है, जिसके बाद शुद्ध धातु प्राप्त करने के लिए शोधन (refining) किया जाता है।
In simple words: (Diagram explanation provided above)

🎯 Exam Tip: Memorize the general flowcharts for extracting metals based on their reactivity, as this helps understand the sequence of processes like roasting, reduction, and refining.

 

Question 44.In the reactivity series of metals, some metals are misplaced. Rearrange these metals in the decreasing order of their reactivity. Zn Na K Mg Ca Al Hg Fe Pb Cu Ag
Answer:K Na Ca Mg Al Zn Fe Pb Cu Hg Ag
ℹ️ चित्र व्याख्या (Diagram Explanation): यह एक धातु की सक्रियता श्रृंखला को दर्शाता है, जिसमें धातुओं को उनकी रासायनिक प्रतिक्रियाशीलता के घटते क्रम में व्यवस्थित किया गया है। पोटेशियम (K) सबसे ऊपर है, जो सबसे अधिक प्रतिक्रियाशील है, और चांदी (Ag) सबसे नीचे है, जो सबसे कम प्रतिक्रियाशील है।
In simple words: The correct decreasing order of reactivity for the given metals is Potassium, Sodium, Calcium, Magnesium, Aluminum, Zinc, Iron, Lead, Copper, Mercury, and Silver.

🎯 Exam Tip: A thorough understanding of the metal reactivity series is crucial for predicting displacement reactions and understanding extraction methods.

 

Question 45.Complete the table, if a metal reacts with the reagent then mark ✓ and if not then X.

Metal	Ferrous sulphate	Silver nitrate	Copper sulphate	Zinc sulphate
Cu
Al

Answer:

Metal	Ferrous sulphate	Silver nitrate	Copper sulphate	Zinc sulphate
Cu	X	✓	X	X
Al	✓	✓	✓	✓

In simple words: Copper reacts only with silver nitrate because it is more reactive than silver. Aluminum, being highly reactive, displaces metals from ferrous, silver, copper, and zinc sulfates.

🎯 Exam Tip: The ability of a metal to displace another metal from its salt solution depends directly on its position in the reactivity series.

 

Question 46.Explain the term corrosion with a suitable example. (OR) What is corrosion ?
Answer:The process in which a metal is destroyed gradually by the action of air, moisture or a chemical (like an acid) on its surface is called corrosion. (OR) Corrosion is degradation of a material due to reaction with its environment. The major problem of corrosion occurs with iron, as it is used as a structural material in construction, bridges, shipbuilding. Iron gets covered by reddish brown flakes when exposed to atmosphere. This is an example of corrosion.
In simple words: Corrosion is the gradual degradation of a metal's surface due to its reaction with environmental factors like air, moisture, or chemicals; rusting of iron is a common example.

🎯 Exam Tip: Define corrosion precisely and provide a clear, common example to illustrate the concept.

 

Question 47.Explain the different methods to prevent corrosion of metals.
Answer:(1) Corrosion of a metal can be prevented if the contact between metal and air is cut off. (2) Corrosion of a metal is prevented by coating with something which does not allow moisture and oxygen to react with it. (3) A layer of oil or paint or grease is applied on the surface of a metal to prevent corrosion. The rusting or corrosion of iron can be prevented by this method. (4) Corrosion is also prevented by coating a corrosive metal with a noncorrosive metal. Galvanising, tinning, electroplating, anodising and alloying are the different methods in which a metal is coated with a noncorrosive metal to prevent corrosion.
In simple words: Corrosion can be prevented by isolating the metal from its environment using coatings like paint, oil, or grease, or by applying a layer of a non-corrosive metal through processes such as galvanizing, tinning, electroplating, anodizing, or alloying.

🎯 Exam Tip: List a variety of prevention methods and briefly explain the underlying principle for each, focusing on breaking contact with corrosive agents.

 

Question 48.Write three methods of preventing rusting of iron.
Answer:1. The rusting of iron can be prevented by painting, oiling, greasing or varnishing its surface. 2. Galvanisation is another method of protecting iron from rusting by coating iron with a thin layer of zinc. 3. Corrosion of iron is prevented by coating iron with noncorrosive substance like carbon. This process is termed as alloying.
In simple words: Rusting of iron can be prevented by painting, oiling, or greasing the surface, by galvanization (coating with zinc), or by alloying iron with non-corrosive substances like carbon.

🎯 Exam Tip: Focus on distinct methods (barrier protection, sacrificial protection, alloying) when listing ways to prevent rusting.

 

Question 49.What is meant by an alloy? Give two examples with chemical composition.
Answer:The homogeneous mixture formed by mixing a metal with other metals or nonmetals in certain proportion is called an alloy. Examples: 1. Bronze: Bronze is an alloy formed from 90% copper and 10% tin. Bronze statues stay well in sun and rain. 2. Stainless steel: Stainless steel alloy is made from 74% iron, 18% chromium and 8% carbon. This alloy does not get stained with air or water and does not rust.
In simple words: An alloy is a homogeneous mixture of a metal with other metals or nonmetals, designed to achieve improved properties like corrosion resistance. Examples include bronze (copper and tin) and stainless steel (iron, chromium, and carbon).

🎯 Exam Tip: Define alloy clearly, and provide examples with their approximate compositions and a key property that makes them useful.

Write Short Notes On The Following:

 

Question 1.Galvanizing.
Answer:(1) The process of coating a thin layer of zinc on iron or steel is called galvanization. (2) In this method corrosion of zinc occurs first because zinc is more electropositive than iron. After a few years zinc layer goes away and the iron layer gets exposed and starts rusting. (3) In galvanization an iron object is dipped into molten zinc. A thin layer of zinc is formed all over the iron object. Examples: Shiny iron nails, pin, iron pipes.
In simple words: Galvanizing is the process of coating iron or steel with a thin layer of zinc to prevent rusting, as the more reactive zinc corrodes sacrificially before the iron.

🎯 Exam Tip: Explain the dual protection mechanism of galvanization: barrier protection and sacrificial protection, along with practical examples.

 

Question 2.Tinning.
Answer:The process of coating a thin layer of tin (molten tin) on copper or brass is called tinning. Cooking vessels made of copper and brass get a greenish coating due to corrosion. The greenish substance is copper carbonate and it is poisonous. If buttermilk or curry is placed in such a vessel it gets spoiled. Therefore, these vessels are coated with tin to prevent corrosion.
In simple words: Tinning is the process of coating copper or brass vessels with a layer of molten tin to prevent corrosion and the formation of poisonous copper carbonate, which can contaminate food.

🎯 Exam Tip: Highlight the importance of tinning for food safety and the specific reason why copper vessels corrode (forming poisonous copper carbonate).

 

Question 3.Electroplating.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख एक साधारण इलेक्ट्रोप्लेटिंग सेल को दर्शाता है। एक सिल्वर एनोड और एक एल्यूमीनियम चम्मच कैथोड के रूप में इलेक्ट्रोलाइटिक समाधान (जैसे सिल्वर नाइट्रेट) में डूबे हुए हैं। एक बाहरी शक्ति स्रोत का उपयोग करके, सिल्वर आयन समाधान से कैथोड पर जमा होते हैं, जिससे एल्यूमीनियम चम्मच पर सिल्वर की एक पतली परत चढ़ जाती है। The process in which a less reactive metal is coated on a more reactive metal by electrolysis is called electroplating. Examples: Silver-plated spoon, gold-plated jewellery. (1) Which process will you study with the help of above material and solutions.
Answer:With the help of above material and solutions, electroplating process is studied.
In simple words: The setup shown is used to study electroplating, which is the process of coating one metal with a thin layer of another, less reactive metal using electrolysis.

🎯 Exam Tip: Identify the components of an electroplating setup and the roles of the anode, cathode, and electrolyte.

 

(2) Define the process.
Answer:The process in which less reactive metal is coated on a more reactive metals by electrolysis is called electroplating.
In simple words: Electroplating uses electrolysis to deposit a thin layer of a less reactive metal onto a more reactive one, enhancing its appearance or protective properties.

🎯 Exam Tip: A precise definition of electroplating, emphasizing the use of electrolysis and the relative reactivity of the metals, is important.

 

(3) Write the anode and cathode reactions.
Answer:At anode: \( \text{Ag} \rightarrow \text{Ag}^+ + \text{e}^- \) At cathode: \( \text{Ag}^+ + \text{e}^- \rightarrow \text{Ag} \)
In simple words: At the anode, silver metal loses electrons to form silver ions, while at the cathode, these silver ions gain electrons to deposit as solid silver.

🎯 Exam Tip: Always specify the oxidation (anode) and reduction (cathode) reactions clearly for electrolysis processes.

 

Question 4.Anodizing. (OR) Identify the process shown in the above diagram and explain it in brief.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख एनोडाइजिंग प्रक्रिया को दर्शाता है, जिसमें एक पावर सप्लाई का उपयोग करके एक धातु (जैसे एल्यूमीनियम) को एनोड के रूप में सल्फ्यूरिक एसिड जैसे इलेक्ट्रोलाइट में डुबोया जाता है। इस प्रक्रिया में, धातु की सतह पर उसके ऑक्साइड की एक मोटी, सुरक्षात्मक परत बनती है। The anodizing technique is an application of electrolysis. In this method copper or aluminium article is used as anode and it is coated with a strong film of their oxides by means of electrolysis. This oxide layer is strong and uniform all over the surface. This thin film protects the metals from corrosion. The protection can be further increased by making the oxide layer thicker during the anodization. Examples: Kitchen articles such as; anodized pressure cooker and anodized pan.
In simple words: Anodizing is an electrolytic process where a thick, protective oxide layer is formed on a metal surface, typically aluminum, to enhance its corrosion resistance and durability.

🎯 Exam Tip: Explain that anodizing is a form of electroplating where the metal itself forms a protective oxide layer, often used for aluminum products.

 

Question 5.Alloying.
Answer:A homogenous mixture of two or more metals or a metal and a nonmetal in a definite proportion is called an alloy. The physical properties of an alloy are different from those of its constituents. Alloys are corrosion resistant. Alloy decreases the intensity of corrosion of metals. Examples: Brass is made from copper and zinc, 90% Copper and 10% tin are used to make an alloy called bronze, Stainless steel is made from 74% iron, 8 % carbon and 18% chromium.
In simple words: Alloying is the process of mixing a metal with other metals or nonmetals to create a new material with enhanced properties like improved corrosion resistance or strength.

🎯 Exam Tip: Define alloying and provide specific examples, detailing the constituent metals and their proportions, to illustrate its practical applications.

Distinguish Between: (Two points of distinction)

 

Question 1.Metals and Nonmetals.
Answer:Metals: 1. Metals have a lustre. 2. They are generally good conductors of heat and electricity. 3. They are generally solids at room temperature. Exception: Mercury and gallium are liquids. 4. Metals form basic oxides. Nonmetals: 1. Nonmetals have no lustre. Exception: Iodine and Diamond. 2. They are bad conductors of heat and electricity. Exception: Graphite. 3. They are generally gases and solids at room temperature. Exception: Bromine is a liquid. 4. Nonmetals form acidic or neutral oxides.
In simple words: Metals typically exhibit luster, conduct heat and electricity well, are solid at room temperature (except mercury, gallium), and form basic oxides, whereas nonmetals generally lack luster (except iodine, diamond), are poor conductors (except graphite), can be solid, liquid or gas at room temperature (except bromine, liquid), and form acidic or neutral oxides.

🎯 Exam Tip: Clearly differentiate metals and nonmetals based on their physical properties (luster, conductivity, state) and chemical properties (oxide nature).

 

Question 2.Roasting and Calcination.
Answer:Roasting: 1. In this process, the ore is heated strongly in the presence of air. 2. In this process, sulphide ore is converted into metal oxide. 3. During this process \( \text{SO}_2 \) is given out. Calcination: 1. In this process, the ore is heated strongly in the limited supply of air. 2. In this process, carbonate ore is converted into metal oxide. 3. During this process \( \text{CO}_2 \) is given out.
In simple words: Roasting involves heating sulphide ores in excess air to convert them into metal oxides, releasing \( \text{SO}_2 \), while calcination involves heating carbonate ores in limited air to convert them into metal oxides, releasing \( \text{CO}_2 \).

🎯 Exam Tip: Focus on the key differences: presence/absence of air, type of ore (sulphide/carbonate), and the gas released (\( \text{SO}_2 \)/\( \text{CO}_2 \)).

Give Scientific Reasons For The Following:

 

Question 1.Calcium floats on water during the reaction with water.
Answer:1. Calcium reacts with water less vigorously hence the heat evolved is not sufficient for hydrogen to catch fire. 2. Instead, calcium floats on water because the bubbles of hydrogen gas formed stick to the surface of the metal.
In simple words: Calcium floats on water because its reaction with water is not vigorous enough to ignite the hydrogen gas produced, and the hydrogen bubbles adhere to the calcium surface, making it buoyant.

🎯 Exam Tip: Understand that the buoyancy is due to hydrogen gas bubbles sticking to the metal, not the metal itself being less dense than water.

 

Question 2.Common salt has high melting and boiling points.
Answer:- Common salt is an ionic compound. Common salt is solid and hard due to strong electrostatic attraction between oppositely charged \( \text{Na}^+ \) and \( \text{Cl}^- \) ions. - A large amount of energy is required to break the strong intermolecular attraction (strong ionic bond). Hence, common salt has high melting and boiling points.
In simple words: Common salt, being an ionic compound, has strong electrostatic forces between its oppositely charged ions, requiring a significant amount of energy to break these bonds, hence its high melting and boiling points.

🎯 Exam Tip: Emphasize the strong electrostatic forces and high energy requirement as the core reasons for high melting/boiling points in ionic compounds.

 

Question 3.Metals are good conductors, while non-metals are poor conductors of electricity.
Answer:- The electrons in the outermost orbit of atoms of a metal are free to move throughout the metal. - When a potential difference is applied between the ends of a metal wire, the net movement of the electrons constitutes an electric current. Hence, metals are good conductors of electricity. - Nonmetals involve covalent bonding and do not have free electrons like metals. Hence, nonmetals are poor conductors of electricity.
In simple words: Metals are good conductors of electricity because they possess free-moving electrons that can carry an electric current, whereas non-metals typically lack these free electrons and are therefore poor conductors.

🎯 Exam Tip: The presence of delocalized (free) electrons is the fundamental reason for electrical conductivity in metals; conversely, their absence explains poor conductivity in most nonmetals.

 

Question 4.Sodium is more reactive than aluminium.
Answer:- If the number of electrons in the outermost orbit of an atom of a metal is less, the metal is more reactive. - Sodium has electronic configuration (2, 8, 1) and aluminium has electronic configuration (2, 8, 3). The number of electrons in the outermost orbit of sodium and aluminium atoms are 1 and 3, respectively. Hence, sodium is more reactive than aluminium.
In simple words: Sodium is more reactive than aluminum because it has fewer valence electrons (one) to lose compared to aluminum (three), making it easier for sodium to achieve a stable electronic configuration and form positive ions.

🎯 Exam Tip: Relate reactivity to the ease of losing valence electrons; fewer valence electrons generally mean higher reactivity for metals.

 

Question 5.When zinc granules are added to copper sulphate solution, the blue coloured solution turns colourless.
Answer:

• Zinc is more reactive than copper.
• When zinc granules are added to copper sulphate solution, they displace copper from the copper sulphate solution to form zinc sulphate solution. As zinc sulphate is colourless, the blue coloured solution of copper sulphate disappears.

In simple words: Zinc is more reactive than copper, so it displaces copper from copper sulfate solution, forming colorless zinc sulfate and causing the blue color to vanish.

🎯 Exam Tip: Understanding the reactivity series of metals is crucial for predicting displacement reactions and their observable changes.

 

Question 6.When an iron nail is dipped into a copper solution, a shiny coat of copper is formed on the nail.
Answer:

• Iron is more reactive than copper.
• When an iron nail is dipped into copper sulphate solution, iron displaces copper from the copper sulphate solution. The copper so liberated deposits on the iron nail. As a result, a shiny coat of copper is formed on the nail.

In simple words: Iron, being more reactive than copper, replaces copper from the copper sulfate solution, causing a shiny layer of copper to deposit on the iron nail.

🎯 Exam Tip: This illustrates a single displacement reaction, where a more reactive metal displaces a less reactive metal from its salt solution, which is a common concept in electrochemistry.

 

Question 7.Cryolite (Na3AlF6) and fluorspar (CaF2) are added to the electrolytic mixture containing pure alumina.
Answer:(1) Alumina has very high melting point (> 2000 °C). Cryolite (Na3AlF6) and fluorspar (CaF2) lower the fusion temperature of the mixture containing alumina from 2000 ° C to 1000 ° C, thereby saving electrical energy. (2) They increase the conductivity and the mobility of the fused mixture. Hence, cryolite and fluorspar are added to the electrolytic mixture containing pure alumina.In simple words: Cryolite and fluorspar are added to alumina during electrolysis to lower its very high melting point, making the process more energy-efficient, and to improve the electrical conductivity of the molten mixture.

🎯 Exam Tip: Remember the dual role of these additives: reducing melting point and enhancing electrical conductivity, which are critical for the economical extraction of aluminium.

 

Question 8.Air is bubbled through the mixture in Froth floatation process.
Answer:(1) In the froth floatation process, in a tank water, ore and an oil are mixed. When air is bubbled through the mixture the oil forms froth. (2) The mineral particles are wetted by the oil and float on the surface. (3) The gangue particles are wetted by water and settle down. Hence, the ore can be concentrated. Hence, air is bubbled through the mixture in froth floatation process.In simple words: Air is bubbled in froth floatation to create a foam with oil that preferentially attaches to the mineral particles, allowing them to float and be separated from the water-wetted gangue.

🎯 Exam Tip: The principle of preferential wetting by oil for mineral particles and by water for gangue, combined with air bubbles creating froth, is key to understanding this concentration method.

 

Question 9.Silver amalgam is used for filling dental cavities.
Answer:(1) Silver is a soft metal and wears off on constant usage particularly due to abrasion. Silver amalgam is an alloy of silver with mercury. (2) It is a hard substance. It is nontoxic. Besides these properties it is a lustrous shining substance. It melts at a comparatively low temperature and can therefore conveniently fill in the cavities. Hence, silver amalgam is used for filling dental cavities.In simple words: Silver amalgam is used for dental fillings because it is a hard, non-toxic, lustrous alloy of silver and mercury that can be easily shaped at low temperatures to fill cavities.

🎯 Exam Tip: Focus on the desirable properties of silver amalgam-hardness, non-toxicity, and low melting point-that make it suitable for dental applications.

 

Explain the following reactions with the help of balanced equations:

 

Question 1.Out of sodium and sulphur which is a metal? Explain its reaction with oxygen. (March 2019)
Answer:Sodium is a metal. Sodium reacts with oxygen in air at room temperature to form sodium oxide. 4Na + O\(_{2}\) \( \longrightarrow \) 2Na\(_{2}\)O Sodium Oxygen Sodium oxideIn simple words: Sodium is a metal that reacts readily with oxygen in the air at room temperature to produce sodium oxide.

🎯 Exam Tip: Remember that sodium is a highly reactive metal, and its reaction with oxygen is a fundamental example of metal oxidation. Balancing the chemical equation correctly is crucial.

 

Question 2.Magnesium burns in air.
Answer:When magnesium burns in air, it combines with oxygen, emitting intense light and heat to form magnesium oxide. 2Mg + O\(_{2}\) \( \longrightarrow \) 2MgO Magnesium Oxygen Magnesium oxideIn simple words: When magnesium burns in air, it vigorously combines with oxygen, releasing intense light and heat, to form magnesium oxide.

🎯 Exam Tip: This reaction is a classic example of a combustion reaction, producing a bright white light and magnesium oxide. Be sure to balance the equation.

 

Question 3.Copper reacts with air.
Answer:Copper tarnishes in moist air and forms black coloured oxide when strongly heated. 2Cu + O\(_{2}\) \[ \xrightarrow{\text{heat}} \] 2CuO Copper Oxygen Copper oxideIn simple words: Copper tarnishes in moist air and forms a black copper oxide when heated strongly.

🎯 Exam Tip: Distinguish between slow tarnishing (oxidation) in moist air and rapid oxidation when strongly heated, both leading to copper oxide formation.

 

Question 4.Sodium reacts with water.
Answer:When sodium reacts with water, it evolves hydrogen which immediately catches fire producing a lot of heat. 2Na + 2H\(_{2}\)O \( \longrightarrow \) 2NaOH + H\(_{2}\) + Heat Sodium Sodium hydroxideIn simple words: Sodium reacts vigorously with water, producing sodium hydroxide, hydrogen gas, and a significant amount of heat, which causes the hydrogen to ignite.

🎯 Exam Tip: Highlight the high reactivity of sodium with water, leading to hydrogen gas ignition due to the exothermic nature of the reaction.

 

Question 5.Calcium reacts with water.
Answer:Calcium reacts with water less vigorously to form hydrogen gas and calcium hydroxide. In this reaction, the heat evolved is not sufficient for hydrogen to catch fire. Ca + 2H\(_{2}\)O \( \longrightarrow \) Ca(OH)\(_{2}\) + H\(_{2}\)(g) Calcium Calcium hydroxide HydrogenIn simple words: Calcium reacts with water to form calcium hydroxide and hydrogen gas, but less vigorously than sodium, and the heat produced is not enough to ignite the hydrogen.

🎯 Exam Tip: Compare the reactivity of calcium with water to that of sodium, noting the difference in reaction vigor and whether the hydrogen gas ignites.

 

Question 6.Steam is passed over aluminium.
Answer:When steam is passed over aluminium, hydrogen gas and aluminium oxide are formed. 2Al(s) + 3H\(_{2}\)O \( \longrightarrow \) Al\(_{2}\)O\(_{3}\)(s) + 3H\(_{2}\)(g) Aluminium Steam Aluminium oxide HydrogenIn simple words: When steam passes over hot aluminium, it produces aluminium oxide and hydrogen gas.

🎯 Exam Tip: Remember that aluminium reacts with steam, not cold or hot water, to form its oxide and hydrogen gas, illustrating its reactivity at higher temperatures.

 

Question 7.Steam is passed over iron.
Answer:When steam is passed over iron, iron (III) oxide and hydrogen gas are formed. 3Fe(s) + 4H\(_{2}\)O \( \longrightarrow \) Fe\(_{3}\)O\(_{4}\) + 4H\(_{2}\)(g) Iron Steam Iron (III) oxide HydrogenIn simple words: Iron reacts with steam to form iron (III) oxide and hydrogen gas.

🎯 Exam Tip: Note the specific oxide formed (Fe3O4) and that this reaction requires steam, not just water, indicating iron's moderate reactivity.

 

Question 8.Magnesium reacts with dil. hydrochloric acid.
Answer:When magnesium reacts with dil. hydrochloric acid, magnesium chloride is formed and hydrogen gas is evolved. Mg(s) + 2HCl(aq) \( \longrightarrow \) MgCl\(_{2}\)(aq) + H\(_{2}\)(g) Magnesium Magnesium chloride HydrogenIn simple words: Magnesium reacts with dilute hydrochloric acid to produce magnesium chloride and hydrogen gas.

🎯 Exam Tip: This is a typical acid-metal reaction where a moderately reactive metal like magnesium displaces hydrogen from an acid. Ensure correct product formation and balancing.

 

Question 9.Aluminium is treated with dil. hydrochloric acid.
Answer:When aluminium is treated with dil. hydrochloric acid, aluminium chloride and hydrogen gas are formed. 2Al(s) + 6HCl(l) \( \longrightarrow \) 2AlCl\(_{3}\)(l) + 3H\(_{2}\)(g) Aluminium metal Aluminium chloride HydrogenIn simple words: Aluminium reacts with dilute hydrochloric acid to yield aluminium chloride and hydrogen gas.

🎯 Exam Tip: Similar to magnesium, aluminium also displaces hydrogen from dilute acids. Pay attention to the stoichiometry of the balanced equation, especially for aluminium chloride.

 

Question 10.Zinc reacts with dil. hydrochloric acid.
Answer:When zinc reacts with dil. hydrochloric acid, zinc chloride and hydrogen gas are formed. Zn + 2HCl \( \longrightarrow \) ZnCl\(_{2}\) + H\(_{2}\)(g) Zinc Zinc chloride HydrogenIn simple words: Zinc reacts with dilute hydrochloric acid to produce zinc chloride and hydrogen gas.

🎯 Exam Tip: Another example of a metal displacing hydrogen from a dilute acid. Recognize zinc as a moderately reactive metal that readily undergoes this reaction.

 

Question 11.Iron is treated with dil. hydrochloric acid.
Answer:When iron reacts with dil. hydrochloric acid, ferrous chloride and hydrogen gas is formed. Fe(s) + 2HCl \( \longrightarrow \) FeCl\(_{2}\)(aq) + H\(_{2}\)(g) Iron Ferrous chloride HydrogenIn simple words: Iron reacts with dilute hydrochloric acid to form ferrous chloride and hydrogen gas.

🎯 Exam Tip: Iron's reaction with dilute acids also produces hydrogen gas and a corresponding iron salt, in this case, iron (II) chloride.

 

Question 12.Copper is reacted with cone, nitric acid.
Answer:When copper is reacted with cone, nitric acid, copper nitrate and reddish brown nitrogen dioxide are formed. Cu(s) + 4HNO\(_{3}\)(aq) \( \longrightarrow \) Cu(NO\(_{3}\))\(_2\)(aq) + 2NO\(_{2}\)(g) + 2H\(_{2}\)O(l) Copper (conc.) Copper nitrate Nitrogen dioxideIn simple words: Copper reacts with concentrated nitric acid to produce copper nitrate, reddish-brown nitrogen dioxide gas, and water.

🎯 Exam Tip: Nitric acid reactions with metals are complex; distinguish between concentrated and dilute acid reactions, as they yield different nitrogen oxides. NO2 is characteristic of concentrated nitric acid.

 

Question 13.Copper is reacted with dil. nitric acid.
Answer:When copper is reacted with dil. nitric acid, copper nitrate and nitric oxide are formed. 3Cu(s) + 8HNO\(_{3}\)(aq) \( \longrightarrow \) 3Cu(NO\(_{3}\))\(_2\)(aq) + 2NO(g) + 4H\(_{2}\)O(l) (dil.) Copper nitrate Nitric oxideIn simple words: Copper reacts with dilute nitric acid to form copper nitrate, nitric oxide gas, and water.

🎯 Exam Tip: Note that dilute nitric acid reacts with copper to produce nitric oxide (NO), a different nitrogen oxide compared to the reaction with concentrated nitric acid (NO2).

 

Question 14.Sodium metal is reacted chlorine gas.
Answer:When sodium metal is reacted with chlorine, sodium chloride an ionic compound is formed. 2Na(s) + Cl\(_{2}\)(g) \( \longrightarrow \) 2NaCl(s) Sodium Chlorine Sodium chloride (Ionic compound)In simple words: Sodium metal reacts with chlorine gas to form sodium chloride, which is an ionic compound.

🎯 Exam Tip: This is a classic example of a metal-nonmetal reaction forming an ionic compound. The transfer of electrons is key to this type of bonding.

 

Question 15.Sulphur burns in air.
Answer:When sulphur burns in air, it combines with oxygen to form acidic sulphur dioxide. S(s) + O\(_{2}\)(g) \[ \xrightarrow{\text{heat}} \] SO\(_{2}\)(g) Sulphur Sulphur dioxideIn simple words: When sulfur burns in air, it combines with oxygen to produce sulfur dioxide, an acidic gas.

🎯 Exam Tip: Nonmetals generally form acidic oxides when they react with oxygen. Sulfur dioxide is a key example of an acidic oxide.

 

Question 16.Chlorine dissolves in water.
Answer:When chlorine dissolves in water, hypochlorous acid is formed. Cl\(_{2}\)(g) + H\(_{2}\)O(l) \( \longrightarrow \) HOCl(aq) + HCl(aq) Chlorine Hypochlorous acidIn simple words: Chlorine gas dissolves in water to form hypochlorous acid and hydrochloric acid.

🎯 Exam Tip: Remember that halogens like chlorine react with water, forming two different acids, with hypochlorous acid being a strong oxidizing agent.

 

Question 17.Chlorine is treated with hydrobromic acid.
Answer:When chlorine is treated with hydrobromic acid, chlorine displaces bromine from hydrobromic acid. Cl\(_{2}\)(g) + 2HBr(aq) \( \longrightarrow \) 2HCl(aq) + Br\(_{2}\)(aq)In simple words: Chlorine, being more reactive than bromine, displaces bromine from hydrobromic acid, forming hydrochloric acid and bromine.

🎯 Exam Tip: This is a halogen displacement reaction, demonstrating the relative reactivity of halogens where a more reactive halogen displaces a less reactive one from its halide solution.

 

Question 18.Hydrogen gas is passed over boiling sulphur.
Answer:When hydrogen gas is passed over boiling sulphur, sulphur combines with hydrogen to form hydrogen sulphide which has rotten egg smell. H\(_{2}\)(g) + S(l) \[ \xrightarrow{\text{high temp.}} \] H\(_{2}\)S\( \uparrow \) (boiling) Hydrogen gasIn simple words: When hydrogen gas is passed over boiling sulfur, they combine to form hydrogen sulfide, known for its rotten egg odor.

🎯 Exam Tip: This reaction forms hydrogen sulfide, a gas recognizable by its distinct unpleasant smell. Note that it requires high temperature.

 

Question 19.Sodium aluminate is treated with water.
Answer:When sodium aluminate is treated with water, it is hydrolysed to give a precipitate of aluminium hydroxide. NaAlO\(_{2}\) + 2H\(_{2}\)O(l) \( \longrightarrow \) NaOH(aq) + Al(OH)\(_{3}\)\( \downarrow \) Sodium aluminate Aluminium hydroxideIn simple words: Sodium aluminate reacts with water in a hydrolysis reaction, producing a precipitate of aluminium hydroxide and sodium hydroxide.

🎯 Exam Tip: This is a hydrolysis reaction, often encountered in the Bayer's process for alumina production. Recognize the formation of aluminium hydroxide precipitate.

 

Question 20.Dry aluminium hydroxide is ignited at 1000 °C.
Answer:When dry aluminium hydroxide is ignited at 1000 °C, alumina (Al\(_{2}\)O\(_{3}\)) formed. 2Al(OH)\(_{3}\) \[ \xrightarrow{\text{heat}} \] Al\(_{2}\)O\(_{3}\) + 3H\(_{2}\)O Aluminium hydroxide 1000 °C Alumina SteamIn simple words: Heating dry aluminium hydroxide at 1000 °C causes it to decompose, forming alumina (aluminium oxide) and water vapor.

🎯 Exam Tip: This is a thermal decomposition reaction. Knowing the decomposition temperature and products (alumina and water) is important for processes like aluminium extraction.

 

Question 21.Zinc sulphide is heated strongly in excess of air.
Answer:When zinc sulphide is heated strongly in excess of air, it forms zinc oxide and sulphur dioxide gas. 2ZnS(s) + 3O\(_{2}\)(g) \[ \xrightarrow{\text{heat}} \] 2ZnO(s) + 2SO\(_{2}\)(g) Zinc sulphide Oxygen Zinc oxide Sulphur dioxideIn simple words: Strongly heating zinc sulfide in abundant air converts it into zinc oxide and releases sulfur dioxide gas.

🎯 Exam Tip: This process is called roasting, a common metallurgical step for sulfide ores. It's an oxidation reaction that converts sulfide to oxide, releasing sulfur dioxide.

 

Question 22.Zinc carbonate is heated strongly in a limited supply of air.
Answer:When zinc carbonate is heated strongly in a limited supply of air, it gives zinc oxide and carbon dioxide. ZnCO\(_{3}\)(s) \[ \xrightarrow{\text{heat}} \] ZnO(s) + CO\(_{2}\)(g) Zinc carbonate Zinc oxide Carbon dioxideIn simple words: Strong heating of zinc carbonate in limited air causes it to decompose, forming zinc oxide and carbon dioxide gas.

🎯 Exam Tip: This process is calcination, used for carbonate ores. It's a thermal decomposition that converts carbonate to oxide, releasing carbon dioxide.

 

Question 23.Zinc oxide is treated with carbon.
Answer:When zinc oxide is treated with carbon, it is reduced to zinc. In this reaction, carbon acts as reducing agent. ZnO + C \( \longrightarrow \) Zn + CO Zinc oxide Carbon Zinc Carbon monoxideIn simple words: When zinc oxide is heated with carbon, carbon acts as a reducing agent to extract zinc metal and form carbon monoxide.

🎯 Exam Tip: Carbon is a common reducing agent for metal oxides. This reduction step is vital in extracting metals like zinc from their oxides.

 

Question 24.Manganese dioxide is heated with aluminium.
Answer:When manganese dioxide is heated with aluminium, manganese dioxide is reduced to manganese and large amount of heat is evolved. 3MnO\(_{2}\) + 4Al \( \longrightarrow \) 3Mn + 2Al\(_{2}\)O\(_{3}\) + heat Manganese dioxide Aluminium Manganese AluminaIn simple words: Heating manganese dioxide with aluminium causes aluminium to reduce manganese dioxide to manganese, releasing a significant amount of heat.

🎯 Exam Tip: This is a thermite-like reaction, where a more reactive metal (aluminium) reduces the oxide of a less reactive metal (manganese), often producing a highly exothermic reaction.

 

Question 25.Cinnabar is heated in air.
Answer:When cinnabar is heated in air, it forms mercuric oxide and sulphur dioxide. 2HgS(s) + 3O\(_{2}\)(g) \[ \xrightarrow{\text{heat}} \] 2HgO(s) + 2SO\(_{2}\)(g) Cinnabar Mercuric oxide Sulphur dioxideIn simple words: When cinnabar (mercuric sulfide) is heated in air, it undergoes roasting to form mercuric oxide and sulfur dioxide.

🎯 Exam Tip: Cinnabar roasting is a classic example of extracting mercury from its sulfide ore, followed by further heating of the oxide to get the metal.

 

Question 26.Cuprous sulphide is heated in air.
Answer:When cuprous sulphide is heated in air, cuprous oxide is formed. Cuprous oxide is reduced to copper in the presence of ore. 2Cu\(_{2}\)S + 3O\(_{2}\) \[ \xrightarrow{\text{heat}} \] 2Cu\(_{2}\)O + 2SO\(_{2}\)(g)\( \uparrow \) Cuprous sulphide Oxygen Cuprous oxide Sulphur dioxide
2Cu\(_{2}\)O + Cu\(_{2}\)S \[ \xrightarrow{\text{heat}} \] 6Cu + SO\(_{2}\)(g)\( \uparrow \) Cuprous oxide Cuprous sulphide Copper Sulphur dioxideIn simple words: Heating cuprous sulfide in air first forms cuprous oxide and sulfur dioxide; then, the cuprous oxide reacts with remaining cuprous sulfide to produce copper metal and more sulfur dioxide.

🎯 Exam Tip: This is an example of auto-reduction or self-reduction, where a portion of the sulfide ore is roasted to oxide, which then reacts with the remaining sulfide to yield the metal without an external reducing agent.

 

Project: (Do it your self)

Project 1. Which metals are used in day to day life? What are its uses?

Project 2. Which nonmetals are used in day to day life? What are its uses?

10th Std Science Part 1 Questions And Answers: