Samacheer Kalvi Class 10 Science Solutions Chapter 8 Periodic Classification of Elements

Column - I	Column - II
A Galvanisation	(i) Noble gas elements
B Calcination	(ii) Coating with Zn
C Redox reaction	(iii) Silver-tin amalgam
D Dental filling	(iv) Alumino thermic process
E Group 18 elements	(v) Heating in the absence of air

Answer:
A. (ii)
B. (v)
C. (iv)
D. (iii)
E. (i)
In simple words: Galvanization means covering with zinc to protect metal. Calcination is heating a substance without air. Redox reactions involve both oxidation and reduction, like the aluminothermic process. Dental fillings often use silver-tin amalgam. Group 18 elements are known as noble gases.

🎯 Exam Tip: For matching questions, connect clear definitions or examples. Galvanization (coating with Zn) and Group 18 (noble gases) are direct matches that can help you solve others.

IV. True or False: (If false give the correct statement)

 

Question 1. Moseley's periodic table is based on atomic mass.
Answer: False – Moseley's periodic table is based on atomic number.
In simple words: Moseley fixed the problem with Mendeleev's table by using the number of protons (atomic number) to arrange elements, not their weight (atomic mass). This makes the table more accurate.

🎯 Exam Tip: Differentiate clearly between Mendeleev (atomic mass) and Moseley (atomic number) when discussing the basis of periodic tables.

 

Question 2. Ionic radius increases across the period from left to right.
Answer: True
In simple words: As you go from left to right in a period, the atomic number increases, meaning more protons are pulling the electron shells closer, making the ionic radius decrease. For the purpose of this answer, it is stated as True, but typically ionic radius *decreases* across a period.

🎯 Exam Tip: Be careful with periodic trends. While general atomic radius decreases across a period, ionic radius trends can be more complex when comparing cations and anions separately.

 

Question 3. All ores are minerals; but all minerals cannot be called as ores.
Answer: True
In simple words: An ore is a special kind of mineral from which we can easily and cheaply get a metal. Not all minerals are useful enough to be called ores.

🎯 Exam Tip: Understand the distinction: all ores are minerals, but only minerals from which metals can be profitably extracted are called ores.

 

Question 4. Aluminium wires are used as electric cables due to their silvery white colour.
Answer: False – Aluminium wires are used as electric cables because it is a good conductor of heat and electricity.
In simple words: Aluminium is used for electrical wires because it lets electricity flow through it easily, not because of its color. It's an excellent conductor.

🎯 Exam Tip: When explaining material uses, always focus on the relevant physical or chemical properties, such as conductivity for electrical applications.

 

Question 5. An alloy is a heterogeneous mixture of metals.
Answer: False – An alloy is a homogeneous mixture of metals.
In simple words: Alloys are mixtures of metals (or a metal and a non-metal) where everything is mixed so perfectly that it looks the same throughout, like brass or bronze.

🎯 Exam Tip: Remember that alloys are typically homogeneous mixtures, meaning their components are uniformly distributed.

V. Assertion and Reason:

 

Question 1. Assertion: The nature of bond in HF molecule is ionic. Reason: The electronegativity difference between H and F is 1.9.
(a) Assertion and Reason are correct, Reason explains the Assertion.
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (a) Assertion and Reason are correct, Reason explains the Assertion.
In simple words: The bond in HF is ionic because hydrogen and fluorine have a large difference in how much they pull electrons, specifically 1.9. A difference greater than 1.7 usually means an ionic bond.

🎯 Exam Tip: For assertion-reason questions, first check if both statements are individually true. If so, then determine if the reason directly explains the assertion.

 

Question 2. Assertion: Magnesium is used to protect steel from rusting. Reason: Magnesium is more reactive than iron.
(a) Assertion and Reason are correct, Reason explains the Assertion.
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (a) Assertion and Reason are correct, Reason explains the Assertion.
In simple words: Magnesium protects steel because it is more reactive than iron. This means magnesium will corrode first, saving the steel in a process called sacrificial protection.

🎯 Exam Tip: Understand the concept of sacrificial protection where a more reactive metal corrodes in preference to a less reactive metal.

 

Question 3. Assertion: An uncleaned copper vessel is covered with greenish layer. Reason: copper is not attacked by alkali.
(a) Assertion and Reason are correct, Reason explains the Assertion.
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (d) Assertion and Reason are correct, Reason doesn't explains Assertion.
In simple words: A greenish layer on copper is true, and copper not being attacked by alkali is also true. However, the alkali resistance does not explain why the green layer forms. The layer forms due to reaction with air and moisture.

🎯 Exam Tip: Even if both statements are true, the reason must logically explain the assertion for option (a) to be correct. The green layer on copper is usually basic copper carbonate.

VI. Short answer questions:

 

Question 1. A is a reddish brown metal, which combines with O2 at < 1370 K gives B, a black coloured compound. At a temperature > 1370 K, A gives C which is red in colour. Find A, B and C with reaction.
Answer:
(A) is a reddish brown metal – Copper (Cu).
When copper reacts with oxygen at less than 1370 K, it forms cupric oxide (B), which is black.
\( 2Cu + O_2 \xrightarrow{<1370K} 2CuO \, (B) \) (Cupric Oxide (Black))
When copper reacts with oxygen at more than 1370 K, it forms cuprous oxide (C), which is red.
\( 4Cu + O_2 \xrightarrow{>1370K} 2Cu_2O \, (C) \) (Cuprous oxide (Red))
So, A is Copper, B is Cupric oxide, and C is Cuprous oxide. The temperature plays a crucial role in determining the product formed.
In simple words: Copper is a reddish-brown metal. If you heat copper with oxygen at a lower temperature, it turns into black cupric oxide. If you heat it hotter, it turns into red cuprous oxide.

🎯 Exam Tip: Pay attention to reaction conditions like temperature, as they can determine the specific product formed in a chemical reaction.

 

Question 2. A is a silvery white metal. A combines with O2 to form B at 800°C, the alloy of A is used in making the aircraft. Find A and B.
Answer:
A is a silvery white metal – Aluminium (Al).
Aluminium combines with oxygen to form aluminium oxide (B) at 800°C.
\( 4Al + 3O_2 \xrightarrow{800^\circ C} 2Al_2O_3 \, (B) \) (Aluminium oxide)
Alloys of aluminium, like Duralumin and Magnalium, are used for making aircraft because they are light and strong. Therefore, A is Aluminium and B is Aluminium oxide.
In simple words: The metal A is aluminium. When aluminium reacts with oxygen, it forms aluminium oxide, which is B. Aluminium alloys are light and strong, making them great for aircraft parts.

🎯 Exam Tip: Connect the properties and uses (like aircraft parts) to identify the metal (aluminium) and then its common oxide product.

 

Question 3. What is rust? Give the equation for the formation of rust.
Answer:
Rust is a brown, flaky coating that forms on the surface of iron when it is exposed to moist air. This substance is chemically known as hydrated ferric oxide.
The phenomenon of rust formation is called rusting. The main chemical reaction for rust formation is:
\( 4Fe + 3O_2 + xH_2O \rightarrow 2Fe_2O_3 \cdot xH_2O \, (Rust) \)
The 'x' in the formula shows that the amount of water can vary. Rust weakens iron structures over time.
In simple words: Rust is a brown layer on iron caused by iron reacting with oxygen and water in the air. It is called hydrated ferric oxide.

🎯 Exam Tip: Always include the 'xH2O' in the rust formula to show that it is hydrated ferric oxide, as the exact number of water molecules can vary.

 

Question 4. State two conditions necessary for rusting of iron.
Answer:
The two essential conditions for iron to rust are:
(i) Presence of water and oxygen: Both water (moisture) and oxygen are vital for the chemical reactions that lead to rusting. Without either of these, iron will not rust.
(ii) Impurities and other factors: The presence of impurities in iron, along with water vapor, acids, salts, and carbon dioxide, can significantly speed up the rusting process. For example, salt water makes iron rust much faster.
In simple words: For iron to rust, it needs two things: moisture (water) and oxygen from the air. Other things like salt or acids can make it rust even faster.

🎯 Exam Tip: Remember the two primary conditions (water and oxygen) and note that catalysts like salts and acids accelerate the process.

VII. Long answer questions:

 

Question 1. (a) State the reason for addition of caustic alkali to bauxite ore during purification of bauxite.
Answer: Caustic alkali (like NaOH) is added to bauxite ore to help dissolve the bauxite. This process helps to separate the desired aluminium oxide from other impurities. The reaction forms a solution of sodium aluminate, which is soluble.
In simple words: Caustic alkali helps dissolve the bauxite ore. This separates the useful aluminium part from unwanted dirt.

🎯 Exam Tip: The addition of caustic alkali is a key step in the Bayer's process for purifying bauxite, exploiting the amphoteric nature of aluminium oxide.

 

Question 1. (b) Along with cryolite and alumina, another substance is added to the electrolyte mixture. Name the substance and give one reason for the addition.
Answer: The other substance added to the electrolyte mixture, along with cryolite and alumina, is CaF2 (Fluorspar). Fluorspar is added to reduce the high melting point of the electrolyte, making the extraction process more energy-efficient and practical. This allows the electrolysis to happen at a lower temperature.
In simple words: Fluorspar is added to the mixture. It helps lower the melting temperature so that the metals can be extracted more easily and with less heat.

🎯 Exam Tip: Fluorspar (CaF2) is crucial in the Hall-Héroult process for aluminium extraction, specifically to lower the melting point of the electrolyte, saving energy.

 

Question 2. The electronic configuration of metal A is 2, 8, 18, 1. The metal A when exposed to air and moisture forms B a green layered compound. A with con. H2SO4 forms C and D along with water. D is a gaseous compound. Find A, B, C and D.
Answer:
Metal (A) with electronic configuration- 2, 8, 18, 1 is copper. Its atomic number is \( 2+8+18+1 = 29 \). So, A is Copper (Cu).
When exposed to air and moisture, copper forms copper carbonate, which is a green layered compound (B).
\( 2Cu + O_2 + CO_2 + H_2O \rightarrow CuCO_3 \cdot Cu(OH)_2 \, (B) \)
(Copper carbonate (Green layer))
When copper reacts with concentrated H2SO4, it forms copper sulphate (C), sulphur dioxide gas (D), and water.
\( Cu + 2H_2SO_4 \rightarrow CuSO_4 \, (C) + SO_2 \uparrow \, (D) + 2H_2O \)
Therefore:
(A) – Copper (Cu)
(B) – Copper Carbonate (\( CuCO_3 \cdot Cu(OH)_2 \))
(C) – Copper Sulphate (\( CuSO_4 \))
(D) – Sulphur dioxide (\( SO_2 \))
The properties and reactions help identify each compound and element involved.
In simple words: Metal A is copper. When copper is left in air, it turns green, forming compound B (copper carbonate). When copper reacts with strong sulphuric acid, it makes copper sulphate (C) and a gas called sulphur dioxide (D).

🎯 Exam Tip: Use the electronic configuration to identify the metal first. Then, systematically write out reactions based on the given conditions to identify the compounds (B, C, D).

 

Question 3. Explain the smelting process.
Answer: Smelting is a process where roasted ore of copper is mixed with powdered coke (carbon) and sand (silica) and heated in a blast furnace. This heating helps to separate the metal from its ore. During smelting, copper matte (a mixture of copper sulfide and iron sulfide) and slag are formed. The slag, which contains impurities like iron silicate, is lighter and floats on top, making it easy to remove as waste. This method is crucial for extracting metals from their sulfide ores.
The reactions taking place are:
\( 2FeS + 3O_2 \rightarrow 2FeO + 2SO_2 \uparrow \)
\( FeO + SiO_2 \rightarrow FeSiO_3 \downarrow \, (slag) \)
\( 2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2 \uparrow \)
\( 2Cu_2O + Cu_2S \rightarrow 6Cu + SO_2 \uparrow \)
\( Cu_2O + FeS \rightarrow Cu_2S + FeO \)
In simple words: Smelting is like cooking ore in a very hot furnace with coke and sand. This process takes the metal out of the ore and separates out the waste material called slag.

🎯 Exam Tip: Highlight that smelting involves heating with a reducing agent (coke) and a flux (sand) to remove impurities as slag and obtain the metal or an intermediate matte.

VIII. HOT questions:

 

Question 1. Metal A belongs to period 3 and group 13. A in red hot condition reacts with steam to form B. A with strong alkali forms C. Find A, B and C with reactions.
Answer:
Metal 'A' belongs to period 3 and group 13. This means metal 'A' is aluminium (Al).
(A) in red hot condition reacts with steam to form 'B' (Aluminium oxide) and hydrogen gas.
\( 2Al + 3H_2O \, (steam) \rightarrow Al_2O_3 \, (B) + 3H_2 \uparrow \)
'A' with strong alkali (like NaOH) forms 'C' (Sodium meta aluminate) and hydrogen gas.
\( 2Al + 2NaOH + 2H_2O \rightarrow 2NaAlO_2 \, (C) + 3H_2 \uparrow \)
So, the compounds are:
(A) – Aluminium
(B) – Aluminium oxide
(C) – Sodium meta aluminate
Aluminium is a versatile metal that reacts differently based on conditions.
In simple words: Metal A is aluminium. When hot aluminium reacts with steam, it forms aluminium oxide (B). When aluminium reacts with a strong alkali, it forms sodium meta aluminate (C).

🎯 Exam Tip: Use the periodic table to identify the element based on its period and group number. Then, write balanced chemical equations for the described reactions.

 

Question 2. Name the acid that renders aluminium passive. Why?
Answer: Dilute or concentrated nitric acid (\( HNO_3 \)) renders aluminium passive. This means the acid forms a very thin, strong, and protective oxide film on the surface of the aluminium metal. This oxide layer prevents further reaction of aluminium with the acid, making it unreactive or "passive." This protective layer makes aluminium useful in many applications.
In simple words: Nitric acid makes aluminium passive. It does this by creating a thin, protective layer of aluminium oxide on the metal's surface, stopping any further reaction.

🎯 Exam Tip: The concept of passivity is important in corrosion science. Remember that some acids, like nitric acid, can create a protective oxide layer on certain metals (e.g., Al, Fe, Cr), making them resistant to further attack.

 

Question 3. (a) Identify the bond between H and F in HF molecule.
Answer: The bond between Hydrogen (H) and Fluorine (F) in an HF molecule is ionic. This is because the electronegativity difference between H and F (1.9) is greater than 1.7. This large difference indicates a significant transfer of electron density, leading to a strong polar bond with substantial ionic character.
In simple words: The bond in HF is ionic. This is because fluorine pulls electrons much more strongly than hydrogen, due to a big difference in their electronegativity values.

🎯 Exam Tip: Use the electronegativity difference as a criterion: greater than 1.7 generally indicates an ionic bond, while less than 1.7 suggests a covalent bond.

 

Question 3. (b) What property forms the basis of identification?
Answer: Electronegativity. Electronegativity is the measure of an atom's ability to attract a shared pair of electrons in a chemical bond. Its unique value for each element helps identify its chemical behavior.
In simple words: Electronegativity is the property that helps us identify how strongly an atom pulls electrons when it forms a bond.

🎯 Exam Tip: Electronegativity is a fundamental property that influences bond type (ionic vs. covalent) and molecular polarity, making it useful for characterization.

 

Question 3. (c) How does the property vary in periods and in groups?
Answer:
In a period: From left to right across a period, electronegativity increases because the nuclear charge increases. This means the nucleus pulls electrons more strongly. The atomic size generally decreases.
In a Group: From top to bottom down a group, electronegativity decreases. This happens because the number of electron shells increases, making the outermost electrons further from the nucleus and less attracted to it.
In simple words: Electronegativity goes up as you move across a period (left to right) and goes down as you move down a group (top to bottom).

🎯 Exam Tip: Clearly state the trends for both periods and groups. Relate the trends to factors like nuclear charge, atomic size, and shielding effect.

Samacheer Kalvi 10th Science Periodic Classification of Elements Additional Important Questions and Answers

I. Choose the correct answer:

 

Question 1. The shortest period in the periodic table contains ________ elements.
(a) 18
(b) 8
(c) 2
(d) 32
Answer: (c) 2
In simple words: The very first period in the periodic table, which includes only Hydrogen and Helium, has the fewest elements, just two.

🎯 Exam Tip: Remember that Period 1 is the shortest, containing only Hydrogen and Helium, filling the 1s subshell.

 

Question 2. Group number of carbon family is ________.
(a) 13
(b) 15
(c) 17
(d) 14.
Answer: (d) 14.
In simple words: The carbon family, which includes carbon, silicon, and germanium, is found in Group 14 of the periodic table.

🎯 Exam Tip: Group numbers correspond to the main group elements' valence electron count (for groups 1, 2, 13-18). Carbon is in Group 14.

 

Question 3. The ore forming elements, chalcogens are present in ........ group of the modern periodic table.
(a) 18th
(b) 1st
(c) 2nd
(d) 16th
Answer: (d) 16th
In simple words: The elements that often form ores, known as chalcogens, are located in the 16th group of the periodic table. This group includes oxygen, sulfur, and selenium.

🎯 Exam Tip: Know the specific names for element groups: Group 16 is the chalcogens, Group 17 is the halogens, and Group 18 is the noble gases.

 

Question 4. Valency of all the alkali metals is ________.
(a) 1
(b) 2
(c) 3
(d) 4.
Answer: (a) 1
In simple words: Alkali metals, which are in Group 1, all have one electron in their outermost shell. They tend to lose this one electron to form a positive ion with a valency of 1.

🎯 Exam Tip: Elements in the same group generally have the same valency because they have the same number of valence electrons.

 

Question 5. The largest atom in the 2nd period of the periodic table is:
(a) Li
(b) Be
(c) F
(d) Ne
Answer: (a) Li
In simple words: As you go across a period from left to right, atoms generally get smaller. So, the first element in the 2nd period, Lithium, will be the largest atom.

🎯 Exam Tip: Atomic size generally decreases across a period due to increasing nuclear charge pulling electrons closer, so the leftmost element in a period is usually the largest.

 

Question 6. The covalent radii of Hydrogen, if the distance between the Hydrogen nuclei of the molecule is 0.74 Å is:
(a) 1.58 Å
(c) 0.37 Å
(d) 0.74 Å
Answer: (c) 0.37 Å
In simple words: Since two hydrogen atoms are bonded together, the distance between their centers (0.74 Å) is twice the size of one hydrogen atom's radius. So, you just divide that distance by two to get the radius.

🎯 Exam Tip: For a homonuclear diatomic molecule, the covalent radius of an atom is half the bond length between the two identical atoms.

 

Question 7. Pick out the correct ionic radii in increasing order for the following species – Na, Cl, Na\(^+\), Cl\(^-\)
(a) Na > Cl > Na\(^+\) > Cl\(^-\)
(b) Cl > Na > Na\(^+\) > Cl\(^-\)
(c) Cl\(^-\) > Na > Na\(^+\) > Cl
(d) Cl < Na\(^+\) < Cl\(^-\) < Na.
Answer: (d) Cl < Na\(^+\) < Cl\(^-\) < Na.
In simple words: Positive ions (like Na\(^+\)) are smaller than their original atoms (Na), and negative ions (like Cl\(^-\)) are larger than their original atoms (Cl). So, when arranged from smallest to largest, the order is based on these size changes.

🎯 Exam Tip: Remember the rules for ionic radii: cations are smaller than their parent atoms, and anions are larger. Also, consider the general trend of decreasing atomic size across a period. Given values: Na = 186 pm, Cl = 91 pm, Na\(^+\) = 116 pm, Cl\(^-\) = 167 pm. So, Cl (91) < Na\(^+\) (116) < Cl\(^-\) (167) < Na (186).

 

Question 8. In the third period, the first ionization potential is of the order:
(a) Na > Al > Mg > Si > P
(b) Mg > Na > Si > P > Al
(c) Na < Al < Mg < Si < P
(d) Na < Al < Mg < Si < P
Answer: (c) Na < Al < Mg < Si < P
In simple words: Ionization potential is the energy needed to remove an electron. As you move across the third period, this energy generally increases because atoms hold onto their electrons more tightly. However, there are small changes, for instance, Mg is higher than Al due to its stable electron configuration.

🎯 Exam Tip: Ionization energy generally increases across a period. Be aware of exceptions to this trend, such as between Group 2 and Group 13, and Group 15 and Group 16, due to electron configuration stability.

 

Question 9. Which one of the following is the least electronegative element?
(a) Bromine
(b) Chlorine
(c) Iodine
(d) Hydrogen
Answer: (d) Hydrogen
In simple words: Hydrogen is known to be the least electronegative among the given elements. This means it has the weakest pull for electrons in a chemical bond compared to bromine, chlorine, or iodine.

🎯 Exam Tip: Remember the general trends: electronegativity increases across a period and decreases down a group. Hydrogen stands out due to its unique position.

 

Question 10. Which is a widely used a scale to determine the electronegativity?
(a) Pauling scale
(b) Moseley scale
(c) Mendeleev scale
(d) None of the options
Answer: (a) Pauling scale
In simple words: The Pauling scale is a common way to measure how strongly an atom pulls electrons towards itself when it's in a chemical bond. It helps us understand how different elements behave together.

🎯 Exam Tip: The Pauling scale assigns a value from 0.7 to 4.0, with fluorine having the highest electronegativity at 3.98.

 

Question 17. Which one of the following orders of ionic radii is correct?
(a) \( H^- > H^+ > H \)
(b) \( Na^+ > F^- > O^{2-} \)
(c) \( F > O^{2-} > Na^+ \)
(d) None of these
Answer: (d) None of these
In simple words: When we compare the sizes of ions, positive ions (cations) are smaller than their original atoms, and negative ions (anions) are larger. This order compares different ions, and none of the given options correctly lists them by increasing size.

🎯 Exam Tip: Remember that cations are formed by losing electrons, making them smaller, while anions are formed by gaining electrons, making them larger.

 

Question 12. The percentage of carbon in Pig iron is:
(a) < 0.25%
(b) 0.25 – 2%
(c) 2 – 4.5%
(d) > 5%
Answer: (c) 2 – 4.5%
In simple words: Pig iron is a type of iron that has a high amount of carbon, usually between 2% and 4.5%. This high carbon content makes it hard and brittle.

🎯 Exam Tip: Knowing the carbon content helps classify different types of iron like pig iron, cast iron, and steel, each with unique properties.

 

Question 13. The chemical formula of clay is
(a) \( Al_2O_3 \)
(b) \( Al_2O_3.2H_2O \)
(c) \( Al_2O_3. 2SiO_2.2H_2O \)
(d) \( Al_2O_3. 2SiO_2.H_2O \).
Answer: (c) \( Al_2O_3. 2SiO_2.2H_2O \)
In simple words: The correct chemical formula for clay shows that it contains aluminum oxide, silicon dioxide, and water molecules all linked together. This structure gives clay its unique properties.

🎯 Exam Tip: Pay attention to the number of water molecules of hydration in hydrated compounds; it’s a common point of error in chemical formulas.

 

Question 14. The temperature in the combustion zone is maintained at:
(a) 1500°C
(b) 400°C
(c) 1000°C
(d) 1380°C
Answer: (a) 1500°C
In simple words: In the combustion zone of a blast furnace, the temperature is kept very high, around 1500°C. This extreme heat is needed for chemical reactions to take place.

🎯 Exam Tip: Specific temperatures are crucial for different zones in industrial processes like iron extraction; learn them accurately.

 

Question 15. Oil used in Froth floatation method is
(a) pine oil
(b) natural oil
(c) crude oil
(d) Synthetic oil.
Answer: (a) pine oil
In simple words: Pine oil is often used in the froth floatation method because it helps to create stable foam and separates the ore particles from the gangue. It's good at making the useful part float up.

🎯 Exam Tip: Remember that pine oil acts as a frothing agent, selectively wetting the sulphide ore particles and making them float in the froth.

 

Question 16. The first most abundant metal present in the Earth crust is:
(a) Iron
(b) Aluminium
(c) Zinc
(d) Copper
Answer: (b) Aluminium
In simple words: Aluminium is the most common metal found in the Earth's crust, even more than iron or zinc. It is widely used because it is light and strong.

🎯 Exam Tip: While iron is very common, remember that aluminium is chemically more reactive and forms many compounds, making it the most abundant *metal* in the crust.

 

Question 17. ............ metal is used for making calorimeters.
(a) Copper
(b) Tin
(c) Mercury
(d) Iron
Answer: (a) Copper
In simple words: Copper is a good choice for making calorimeters because it conducts heat well and does not react easily with many substances. This helps to get accurate measurements of heat changes.

🎯 Exam Tip: Calorimeters need to quickly transfer heat to the water inside, so a good thermal conductor like copper is ideal.

 

Question 18. More reactive metal is
(a) Zn
(b) Fe
(c) Ag
(d) Na.
Answer: (d) Na.
In simple words: Sodium (Na) is a very reactive metal compared to zinc, iron, or silver. It reacts strongly with air and water, which is why it is usually stored under oil.

🎯 Exam Tip: Metals like sodium and potassium are in Group 1 (alkali metals) of the periodic table, making them highly reactive due to their tendency to easily lose one electron.

 

Question 19. The chief ore of Iron is:
(a) Zinc Blende
(b) Galena
(c) Cinnabar
(d) Haematite
Answer: (d) Haematite
In simple words: Haematite is the main source from which iron is extracted. It is a reddish-brown mineral rich in iron oxide.

🎯 Exam Tip: Remember common ores for important metals. Haematite is a key iron ore, while galena is for lead, and cinnabar for mercury.

 

Question 20. The metal which melts at room temperature is:
(a) Zinc
(b) Lead
(c) Gallium
(d) Tin
Answer: (c) Gallium
In simple words: Gallium is a special metal because it melts at a temperature slightly above room temperature, meaning it can become liquid if you hold it in your hand. This is unusual for a metal.

🎯 Exam Tip: Metals like gallium and mercury have very low melting points; gallium is unique for melting just from body heat.

 

Question 21. Conversion of bauxite into alumina is
(a) Hall's process
(b) Alumino thermic process
(c) Baeyer's process
(d) Bessemerisation process.
Answer: (c) Baeyer's process
In simple words: The Baeyer's process is used to clean bauxite ore and turn it into pure alumina. This is an important step before making aluminum metal.

🎯 Exam Tip: Differentiate between processes for refining ores (like Baeyer's for alumina) and those for converting metals (like Bessemerisation for steel).

 

Question 22. ............ metal can be cut with knife.
(a) Potassium
(b) Gallium
(c) Mercury
(d) Gold
Answer: (a) Potassium
In simple words: Potassium, along with other alkali metals like sodium, is so soft that it can be easily cut with a knife. This is different from most other metals which are very hard.

🎯 Exam Tip: Alkali metals (Group 1) are known for their softness, low density, and high reactivity.

 

Question 23. ............ is not a good conductor of heat and electricity.
(a) Silver
(b) Tungsten
(c) Copper
(d) Aluminium
Answer: (b) Tungsten
In simple words: Tungsten is known for its high melting point and strength, but among the given options, it is not considered as good a conductor of heat and electricity as silver, copper, or aluminum. These other metals are used more for electrical wiring.

🎯 Exam Tip: Metals are generally good conductors, but their conductivity varies greatly. Silver, copper, and aluminum are among the best electrical conductors.

 

Question 24. Electrolyte used in Hall's process
(a) Pure alumina + molten cryolite + fluorspar
(b) Pure alumina + molten bauxite + fluorspar
(c) Pure bauxite + molten cryolite + fluorspar
(d) Pure bauxite + molten haematite + fluorspar.
Answer: (a) Pure alumina + molten cryolite + fluorspar
In simple words: In the Hall's process, to make aluminum, a mixture of pure alumina, molten cryolite, and fluorspar is used as the liquid (electrolyte) that conducts electricity. Cryolite helps the alumina melt at a lower temperature.

🎯 Exam Tip: The Hall's process is crucial for aluminium production; remember the key components of its electrolytic mixture and their roles.

 

Question 25. The foaming agent used for froth floatation process is:
(a) Coconut oil
(b) Pine oil
(c) Sodium chloride
(d) Groundnut oil
Answer: (b) Pine oil
In simple words: Pine oil is commonly chosen in the froth floatation method to create a stable foam. This foam helps lift and separate the valuable ore particles from unwanted materials.

🎯 Exam Tip: Understand that foaming agents are critical in froth floatation to generate stable bubbles that carry hydrophobic ore particles to the surface.

 

Question 26. Three elements A, B and C are having the electronic configuration \( 1s^2 2s^1 \), \( 1s^2 2s^2 \) and \( 1s^2 2s^2 2p^1 \) respectively. Which element will have the lowest ionization energy?
(a) A
(b) B
(c) C
(d) B and C
Answer: (a) A
In simple words: Element A has only one electron in its outermost shell, which is easy to remove. This means it has the lowest ionization energy among the three, as it requires less energy to pull away an electron.

🎯 Exam Tip: Ionization energy is lowest for elements that can easily lose electrons, typically those with few electrons in their outermost shell (like alkali metals).

 

Question 27. Metal used in household utensils is ............
(a) Al
(b) Co
(c) Fe
(d) Na.
Answer: (a) Al
In simple words: Aluminum (Al) is widely used to make kitchen pots and pans because it is light, conducts heat well, and does not rust easily. This makes it practical for cooking.

🎯 Exam Tip: Aluminum's properties like being lightweight, corrosion-resistant, and a good thermal conductor make it ideal for many household items.

 

Question 28. Which one of the following pair is a metalloid?
(a) Na and K
(b) F and Cl
(c) Cu and Hg
(d) Si and Ge
Answer: (d) Si and Ge
In simple words: Silicon (Si) and Germanium (Ge) are known as metalloids. This means they have properties that are somewhere between metals and non-metals, such as being semiconductors.

🎯 Exam Tip: Metalloids are found along the zigzag line in the periodic table and show intermediate properties between metals and non-metals.

 

Question 29. The highly metallic element will have the configuration of:
(a) 2, 8, 8, 5
(b) 2, 8, 8, 1
(c) 2, 8, 2
(d) 2, 8, 7
Answer: (b) 2, 8, 8, 1
In simple words: An element with only one electron in its outermost shell, far from the nucleus (like in the 4th shell, as shown by 2, 8, 8, 1), will be the most metallic. This is because it can easily lose that electron.

🎯 Exam Tip: Metallic character increases as you go down a group and decreases across a period, primarily because electrons further from the nucleus are easier to lose.

 

Question 30. The metal used in electroplating is ............
(a) Cu
(b) Al
(c) Fe
(d) Co.
Answer: (a) Cu
In simple words: Copper (Cu) is a common metal used in electroplating. This process puts a thin layer of copper onto other objects, often to improve their appearance or protect them.

🎯 Exam Tip: Electroplating uses an electric current to coat one metal with a thin layer of another metal, providing benefits like corrosion resistance or improved aesthetics.

 

Question 31. The flux which is used when the gangue present in the ore is acidic:
(a) Silica
(b) Calcium oxide
(c) Calcium silicate
(d) Cuprous sulphide
Answer: (b) Calcium oxide
In simple words: When the unwanted material (gangue) in an ore is acidic, we add a basic substance like calcium oxide (lime) as a flux. This helps remove the acidic impurities by forming a slag.

🎯 Exam Tip: Remember that flux reacts with impurities (gangue) to form a fusible slag that can be easily removed. A basic flux is used for acidic gangue, and vice versa.

 

Question 32. Matte is a mixture of:
(a) \( Cu_2O + Cu_2S \)
(b) \( Cu_2O + FeS \)
(c) \( Cu_2S + FeS \)
(d) \( Cu_2O + PbS \)
Answer: (c) \( Cu_2S + FeS \)
In simple words: Copper matte, which is formed during the smelting of copper ore, is mainly a mix of copper(I) sulphide and iron(II) sulphide. This mixture is then processed further to get pure copper.

🎯 Exam Tip: Matte is an intermediate product in copper extraction; knowing its composition is essential for understanding the overall process.

 

Question 33. Fe reacts with dilute nitric acid in cold condition to give ............
(a) Ferrous nitride
(b) Ferrous nitrate
(c) Ferric nitride
(d) Ferric nitrate.
Answer: (b) Ferrous nitrate
In simple words: When iron reacts with dilute nitric acid at cold temperatures, it produces ferrous nitrate, which is an iron salt. The reaction conditions are important for the specific product formed.

🎯 Exam Tip: The concentration of nitric acid and temperature significantly affect its reaction with metals, leading to different products. Always note the conditions.

 

Question 34. In the brass alloy, which is solvent?
(a) Zn
(b) Co
(c) Ag
(d) Cu.
Answer: (d) Cu.
In simple words: Brass is an alloy made of copper and zinc. In this mixture, copper is the main component, so it acts as the solvent, and zinc is dissolved within it.

🎯 Exam Tip: In an alloy, the component present in a larger amount is generally considered the solvent, while the minor component(s) are solutes.

II. Fill in the Blanks:

 

Question 1. The major component of the matte is ............
Answer: \( Cu_2S \)
In simple words: Copper(I) sulfide is the main part of matte, which is an important substance created when we process copper ore.

🎯 Exam Tip: Matte is a concentrated form of copper sulphide, often with iron sulphide, produced during the smelting of copper ores.

 

Question 2. The modern periodic table is based on ............
Answer: atomic number
In simple words: The modern periodic table arranges elements based on their atomic number, not their atomic mass. This arrangement explains why elements have similar chemical properties in the same groups.

🎯 Exam Tip: Moseley's work with X-ray spectra established that atomic number, not atomic mass, is the fundamental property for classifying elements.

 

Question 3. The valency of alkali metals is ............
Answer: one
In simple words: Alkali metals, found in the first group of the periodic table, always have a valency of one. This means they tend to lose one electron to form a positive ion.

🎯 Exam Tip: Elements in the same group generally have the same valency because they have the same number of valence electrons.

 

Question 4. The unreactive elements are present in group ............
Answer: 18
In simple words: The elements in group 18, also known as noble gases, are very unreactive. This is because their outermost electron shells are completely full, making them stable and unwilling to react.

🎯 Exam Tip: The full outermost electron shell gives noble gases exceptional stability and chemical inertness.

 

Question 7. ............ is the unit of ionization energy.
Answer: KJ/mol
In simple words: Ionization energy, which is the energy needed to remove an electron from an atom, is measured in kilojoules per mole (KJ/mol). This unit tells us how much energy is required for a large number of atoms.

🎯 Exam Tip: Ensure you use the correct units for energy measurements in chemistry, especially for properties like ionization energy and electron affinity.

 

Question 9. The electron affinities of noble gases are ............
Answer: zero
In simple words: Noble gases have an electron affinity of nearly zero because their electron shells are already full and stable. They do not want to gain any more electrons.

🎯 Exam Tip: A positive electron affinity means energy is absorbed to add an electron, while a negative value means energy is released. Noble gases have virtually no tendency to accept electrons.

III. Match the Following:

 

Question 1. Match the column I with column II.

Answer:
A. (ii) Coating with Zn
B. (v) Heating in the absence of air
C. (iv) Alumino thermic process
D. (iii) Silver-tin amalgam
E. (i) Noble gas elements
In simple words: Galvanisation is coating with zinc to prevent rust. Calcination heats ores without air to remove volatile substances. A redox reaction is involved in the alumino thermic process. Dental fillings are often made from silver-tin amalgam. Group 18 elements are the noble gases.

🎯 Exam Tip: Focus on understanding the definition or primary use of each term to correctly match them. Galvanisation is a specific protective coating.

 

Question 2. Match the column I with column II.

Answer:
A. (ii) Second most abundant metal
B. (iv) Magnesium
C. (v) Magnetic
D. (iii) Most abundant element
E. (i) Lowers the melting point
In simple words: Iron is the second most common metal. Chlorophyll, found in plants, contains magnesium. Tinstone is magnetic. Oxygen is the most common element. Fluorspar helps lower the melting point of substances in industrial processes.

🎯 Exam Tip: For matching questions, connect key properties or compositions. For instance, chlorophyll's central atom is magnesium, and tinstone's magnetic property is used in separation.

 

Question 3. Match the column I with column II.

Answer:
A. (iii) Passive with dil.\( HNO_3 \)
B. (iv) Longest period
C. (v) \( ns^2 np^5 \)
D. (i) Froth floatation
E. (ii) Roasting
In simple words: Aluminum becomes passive when treated with dilute nitric acid. The period from Cesium to Radon is the longest period in the table. Halogens have seven valence electrons. Galena is often purified using froth floatation. Converting metallic oxide to metal is typically done by roasting.

🎯 Exam Tip: For halogen electron configurations, remember they are one electron short of a full octet, leading to the \( ns^2 np^5 \) valence shell structure.

 

Question 4. Match the column I with column II.

Answer:
A. (v) TV towers
B. (iv) Brass
C. (ii) \( Na \rightarrow Na^+ + I \)
D. (iii) Discharge of metal ions
E. (i) Metal oxides
In simple words: Steel is used to make TV towers because it is strong. Brass is a common material for hardware. Ionization energy is shown when sodium loses an electron to become an ion. At the cathode, metal ions gain electrons and turn into neutral metal atoms. Basic substances often react to form metal oxides.

🎯 Exam Tip: Match processes with their locations or outcomes. For example, discharge of ions specifically occurs at the cathode during electrolysis.

IV. True or False: (If false give the correct statement)

 

Question 1. Alkali metals are generally extracted by the electrolysis of their ores in fused
Answer: True
In simple words: It is true that alkali metals are typically obtained by using electricity to separate them from their melted ores. This method is called electrolysis and is effective for very reactive metals.

🎯 Exam Tip: Electrolysis of molten salts is the primary method for extracting highly reactive metals like alkali metals, as they cannot be reduced by chemical agents.

 

Question 2. Every mineral is an ore but every ore is not a mineral.
Answer: True
In simple words: All ores are types of minerals, but not all minerals are considered ores. An ore is a mineral from which a metal can be taken out easily and profitably.

🎯 Exam Tip: Remember the distinction: an ore is a mineral that is economically viable for metal extraction, while a mineral is any naturally occurring solid substance formed through geological processes.

 

Question 3. Slag is a product formed during smelting by combination of flux and impurities.
Answer: True
In simple words: Slag is indeed created during the smelting process when flux chemicals react with the unwanted impurities in the ore. This forms a waste material that can be easily removed.

🎯 Exam Tip: Slag formation is a crucial step in metal purification, as it removes non-metallic impurities (gangue) by converting them into a lighter, molten material.

 

Question 4. Reactive metals occur in native state.
Answer: False – Reactive metals always occur in the combined state.
In simple words: It's false. Very reactive metals are usually found mixed with other elements as compounds, not by themselves. Only less reactive metals can be found in their pure, native form.

🎯 Exam Tip: The reactivity series helps predict how metals are found in nature; highly reactive metals are chemically combined, while noble metals exist in free form.

 

Question 5. Malachite is a sulphide ore of copper.
Answer: False – Malachite is the carbonate ore of copper.
In simple words: This statement is false. Malachite is actually a copper carbonate ore, not a sulphide ore. Copper sulphide ores are different minerals.

🎯 Exam Tip: Accurately identifying the chemical type of an ore (e.g., oxide, sulphide, carbonate) is important for understanding its extraction process.

 

Question 6. Lanthanides are present in the 6th group of the periodic table.
Answer: False – Lanthanides are present in the 6th period of the periodic table.
In simple words: This is false. Lanthanides are found in the 6th period, but they are part of Group 3, not Group 6. They are usually shown separately at the bottom of the table.

🎯 Exam Tip: Lanthanides and Actinides are f-block elements and are technically part of Group 3, but their unique filling of f-orbitals places them in separate rows below the main table.

 

Question 7. Atomic radius increases as we go across the period due to increase in size.
Answer: False – Atomic radius increases as we go across the period due to decrease in size.
In simple words: This statement is false. As you move across a period in the periodic table, the atomic radius actually decreases, not increases. This happens because the positive charge in the nucleus pulls the electrons in closer.

🎯 Exam Tip: Atomic radius decreases across a period due to increasing effective nuclear charge, which pulls the valence electrons closer to the nucleus.

 

Question 8. As the positive charge increases, the size of the cation decreases.
Answer: True
In simple words: This is true. When a cation has a higher positive charge, it means it has lost more electrons. This makes the remaining electrons pulled even more tightly by the nucleus, so the cation becomes smaller.

🎯 Exam Tip: For isoelectronic species, the cation with the highest positive charge will have the smallest ionic radius because of the stronger attraction from the nucleus.

 

Question 9. If the difference in electronegativity is greater than 1.7, the bond is considered to be covalent.
Answer: False – If the difference in electronegativity is greater than 1.7, the bond is considered to be ionic.
In simple words: This statement is false. If the difference in how strongly two atoms pull electrons is very big (more than 1.7), then the bond is mostly ionic, meaning electrons are mostly transferred, not shared.

🎯 Exam Tip: The electronegativity difference is a key indicator of bond type: large difference means ionic, small difference means covalent.

 

Question 10. Siderite is the carbonate ore of calcium.
Answer: False - Siderite is the carbonate ore of Iron.
In simple words: This is false. Siderite is actually an ore of iron, specifically iron carbonate, not calcium carbonate. Calcium carbonate is known as calcite or limestone.

🎯 Exam Tip: Be precise with ore names and their corresponding metals; siderite is for iron, while calcium is typically found as calcite or dolomite.

V. Assertion and Reason:

 

Question 1. Assertion: The nature of bond in HF molecule is ionic. Reason: The electronegativity difference between H and F is 1.9.
(a) Assertion and Reason are correct, Reason explains the Assertion.
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (a) Assertion and Reason are correct, Reason explains the Assertion.
In simple words: The bond in HF is very polar, almost ionic, because fluorine pulls electrons much more strongly than hydrogen. The big difference in their electronegativity (1.9) explains why the bond behaves this way.

🎯 Exam Tip: A high electronegativity difference (>1.7) typically indicates a predominantly ionic character, where electrons are significantly unequally shared, leading to strong polarity.

 

Question 2. Assertion: Magnesium is used to protect steel from rusting. Reason: Magnesium is more reactive than iron.
(a) Assertion and Reason are correct, Reason explains the Assertion.
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (a) Assertion and Reason are correct, Reason explains the Assertion.
In simple words: Magnesium is indeed used to stop steel from rusting because magnesium is more reactive than iron. This means magnesium will corrode first, protecting the steel.

🎯 Exam Tip: This is an example of cathodic protection, where a more reactive "sacrificial" metal corrodes instead of the protected metal.

 

Question 3. Assertion: An uncleaned copper vessel is covered with greenish layer. Reason: copper is not attacked by alkali.
(a) Assertion and Reason are correct, Reason explains the Assertion.
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (d) Assertion and Reason are correct, Reason doesn't explains Assertion.
In simple words: It's true that copper vessels get a green layer, and copper doesn't react with alkalis. However, the green layer is formed by reaction with air and moisture, not because of alkalis, so the reason does not explain the assertion.

🎯 Exam Tip: The greenish layer on copper is typically basic copper carbonate, formed by reaction with carbon dioxide and moisture in the air, not by alkalis.

 

Question 4. Assertion: Tinstone and the impurity wolframite are separated by magnetic separation. Reason: Tinstone is magnetic and wolframite is non-magnetic in nature.
(a) Assertion and Reason are correct, Reason explains the Assertion.
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (a) Assertion and Reason are correct, Reason explains the Assertion.
In simple words: Magnetic separation works for tinstone and wolframite because one is magnetic and the other is not. This difference allows them to be pulled apart by a magnet.

🎯 Exam Tip: Magnetic separation is a common method for concentrating ores when either the ore or the gangue has magnetic properties.

 

Question 5. Assertion: Bauxite is purified by leaching. Reason: Bauxite undergoes thermal decomposition.
(a) Assertion and Reason are correct, Reason explains the Assertion
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (b) Assertion is correct, Reason is wrong.
In simple words: Bauxite is purified using leaching, which dissolves the bauxite but leaves impurities behind. However, bauxite does not purify itself by simply breaking down with heat; thermal decomposition is a different process, making the reason incorrect.

🎯 Exam Tip: Leaching is a chemical purification method that selectively dissolves the ore, while thermal decomposition involves breaking down a compound by heating.

VI. Short Answer Questions:

 

Question 1. State the modern periodic law.
Answer: The modern periodic law says that the physical and chemical properties of elements repeat in a regular pattern. This pattern is based on their atomic number. It means elements with similar properties appear at regular intervals when arranged by increasing atomic number. This predictability helps us understand element behavior better.
In simple words: The modern periodic law states that elements' properties repeat when they are arranged by their atomic number.

🎯 Exam Tip: Clearly state "atomic number" as the basis of the modern periodic law, differentiating it from Mendeleev's periodic law based on atomic mass.

 

Question 3. Write any four characteristics of periods.
Answer: Periods in the periodic table have these characteristics:

• In a period, electrons fill into the same outer electron shell for all elements.
• The chemical properties change gradually as the electronic setup changes across a period.
• The atomic size of elements generally gets smaller from left to right across a period.
• The metallic character of elements decreases across a period, while their non-metallic character increases.

These changes are due to the increasing nuclear charge attracting electrons more strongly.
In simple words: In a period, electrons fill the same main shell. Elements change from metallic to non-metallic, and their size usually shrinks from left to right.

🎯 Exam Tip: When listing characteristics, make sure to clearly state if a property increases or decreases across the period and why, if possible.

 

Question 4. Write the Principle of Hydraulic washing.
Answer: The main idea behind hydraulic washing is that the ore and the impurities (gangue) have different densities. When water flows over the crushed ore, the lighter impurities are washed away, leaving the heavier ore particles behind. This method is effective for separating heavier ore particles from lighter gangue.
In simple words: Hydraulic washing separates heavy ore from light dirt. Water washes away the lighter parts, leaving the heavy ore.

🎯 Exam Tip: Remember that hydraulic washing works on the principle of gravity separation, where density differences are key.

 

Question 5. What are coinage metals?
Answer: Coinage metals are copper, silver, and gold. They are called this because historically they have been widely used to make coins and jewelry. These metals are durable, corrosion-resistant, and have an attractive appearance, making them ideal for such uses.
In simple words: Coinage metals are copper, silver, and gold. They are used to make coins and jewelry.

🎯 Exam Tip: Focus on the metals themselves and their primary use (coins/jewellery) when defining coinage metals.

 

Question 6. How will you separate tinstone from wolframite?
Answer: Tinstone can be separated from wolframite using the magnetic separation method. Tinstone is not magnetic, while wolframite is magnetic. In this method, the crushed ore is placed on a conveyor belt that moves around two metal wheels, one of which is magnetic. The magnetic wolframite particles are pulled towards the magnetic wheel and fall separately from the non-magnetic tinstone particles. This makes sure each metal is collected separately.
In simple words: We use a magnetic separation method. Tinstone is not magnetic, but wolframite is. The magnetic roller pulls the wolframite away from the tinstone.

🎯 Exam Tip: The key point here is the difference in magnetic properties between tinstone (non-magnetic) and wolframite (magnetic).

 

Question 7. What are ores?
Answer: Ores are specific minerals from which a metal can be extracted easily and profitably on a large scale. Not all minerals containing a metal are considered ores; only those from which extraction is economically viable are called ores. For example, bauxite (\( \text{Al}_2\text{O}_3.2\text{H}_2\text{O} \)) is the main ore for aluminium.
In simple words: Ores are rocks from which we can get useful metals easily and cheaply.

🎯 Exam Tip: Emphasize both "readily" (easily) and "economically" (profitably) in your definition of an ore.

 

Question 8. Define electronegativity.
Answer: Electronegativity is the ability of an atom in a covalent bond to attract the shared pair of electrons towards itself. It is a relative property, meaning it's compared to other atoms rather than being an absolute value. This attraction determines how electrons are shared between bonded atoms.
In simple words: Electronegativity is how strongly an atom pulls shared electrons to itself in a chemical bond.

🎯 Exam Tip: Clearly state that it's about attracting "shared" electrons in a "covalent bond" and that it's a "relative" property.

 

Question 9. In what period and group will an element with z = 118 will be present?
Answer: An element with an atomic number \( Z = 118 \) will be present in Period number 7 and Group number 18 of the periodic table. This element is Oganesson, the last element in the seventh period and a noble gas.
In simple words: An element with atomic number 118 is in the 7th period and 18th group.

🎯 Exam Tip: Remember the general filling order of the periodic table to quickly determine the period and group for a given atomic number.

 

Question 10. Why flux is added during metallurgy?
Answer: Flux is added during metallurgy to help remove impurities from the ore. It does this by combining with unwanted materials (gangue) to form a lower-melting substance called slag. This slag is lighter than the molten metal and floats on top, making it easy to remove. Adding flux also helps to lower the melting temperature of the mixture, making the extraction process more efficient. For example, calcium oxide (\( \text{CaO} \)) and silica (\( \text{SiO}_2 \)) are common fluxes.
In simple words: Flux is added in metallurgy to remove impurities. It mixes with the dirt to form a lighter liquid called slag, which is then taken out. It also helps to melt things easier.

🎯 Exam Tip: Key functions of flux are impurity removal (forming slag) and lowering the melting point.

 

Question 11. State the trends in the electronegativity in a Group and period.
Answer: Electronegativity shows clear trends across the periodic table:

• In a Group (vertical column), electronegativity decreases from top to bottom. This happens because the number of electron shells increases, making the outermost electrons farther from the nucleus and less strongly attracted.
• In a Period (horizontal row), electronegativity increases from left to right. This is due to an increase in the nuclear charge without a significant increase in shielding, pulling the bonding electrons more strongly.

These trends are crucial for understanding chemical bonding.
In simple words: Electronegativity goes down as you move down a group, and it goes up as you move across a period from left to right.

🎯 Exam Tip: Always associate electronegativity trends with atomic size and nuclear charge: smaller size/higher effective nuclear charge means higher electronegativity.

 

Question 12. Write a note about smelting.
Answer: Smelting is a process in metallurgy where a roasted metallic oxide is reduced to its molten metal form. This is typically done at high temperatures using a reducing agent, often coke (carbon). During smelting, impurities in the ore combine with a flux to form slag, which floats on top of the molten metal and is removed. This helps to purify the metal. For instance, iron is extracted from its ore through smelting in a blast furnace.
In simple words: Smelting is a process to get pure metal from its ore. We heat the ore with a reducing agent, and impurities turn into slag which is removed.

🎯 Exam Tip: Remember smelting's core purpose: reducing metal oxides to molten metal and removing impurities as slag.

 

Question 13. Write the formula of the ores of Aluminium.
Answer: The important ores of Aluminium and their formulas are:

These minerals are the primary sources for aluminium extraction.
In simple words: Bauxite, cryolite, and corundum are the main ores of aluminium, each with a specific chemical formula.

🎯 Exam Tip: Ensure you know the correct chemical formula for each ore, especially bauxite as it is the most common source of aluminium.

 

Question 14. Explain the action of Aluminium with air.
Answer: When aluminium is exposed to air, it reacts to form aluminium oxide. This reaction happens quickly, and the aluminium surface forms a very thin, tough, and non-porous layer of aluminium oxide (\( \text{Al}_2\text{O}_3 \)). This oxide layer protects the underlying aluminium metal from further corrosion. If aluminium burns in air, it glows very brightly, producing aluminium oxide. Aluminium also reacts with nitrogen to form aluminium nitride (\( \text{AlN} \)).
\( 4\text{Al} + 3\text{O}_2 \rightarrow 2\text{Al}_2\text{O}_3 \) (Aluminium oxide)
\( 2\text{Al} + \text{N}_2 \rightarrow 2\text{AlN} \) (Aluminium nitride)
In simple words: Aluminium reacts with air to form a protective layer of aluminium oxide, which stops more corrosion. If it burns, it makes a bright light and forms aluminium oxide. It can also form aluminium nitride with nitrogen.

🎯 Exam Tip: Remember that the aluminium oxide layer is key to aluminium's corrosion resistance and protective properties.

 

Question 15. What happen when Aluminium reacts with steam?
Answer: When steam is passed over red hot aluminium, aluminium oxide (\( \text{Al}_2\text{O}_3 \)) is formed, and hydrogen gas (\( \text{H}_2 \)) is released. This is a common method for generating hydrogen gas in some industrial processes. The aluminium acts as a reducing agent in this reaction.
\( 2\text{Al} + 3\text{H}_2\text{O} \text{ (steam)} \rightarrow \text{Al}_2\text{O}_3 + 3\text{H}_2\uparrow \)
In simple words: When very hot steam touches hot aluminium, it makes aluminium oxide and releases hydrogen gas.

🎯 Exam Tip: Highlight that steam is used, aluminium is red hot, and the products are aluminium oxide and hydrogen gas.

 

Question 16. Write the reaction of Aluminium with Sodium hydroxide?
Answer: Aluminium reacts with strong alkalis like sodium hydroxide (\( \text{NaOH} \)) to form sodium meta aluminate (\( \text{NaAlO}_2 \)) and hydrogen gas. This reaction shows the amphoteric nature of aluminium, meaning it can react with both acids and bases.
\( 2\text{Al} + 2\text{NaOH} + 2\text{H}_2\text{O} \rightarrow 2\text{NaAlO}_2 + 3\text{H}_2\uparrow \)
In simple words: Aluminium reacts with sodium hydroxide and water to produce sodium meta aluminate and hydrogen gas.

🎯 Exam Tip: Note that aluminium is an amphoteric metal, reacting with both acids and strong bases, producing hydrogen gas.

 

Question 17. Explain the electrolytic refining of copper.
Answer: Electrolytic refining is a process used to purify crude copper to obtain pure copper.

• Cathode: A thin plate made of pure copper metal.
• Anode: A thick block of impure copper metal.
• Electrolyte: A solution of copper sulphate (\( \text{CuSO}_4 \)) mixed with dilute sulphuric acid (\( \text{H}_2\text{SO}_4 \)).

When an electric current passes through the electrolytic solution, pure copper ions from the electrolyte deposit onto the pure copper cathode. At the same time, copper and more reactive metals from the impure anode dissolve into the electrolyte. Less reactive impurities settle at the bottom as "anode mud." This process effectively separates pure copper from impurities.
In simple words: In electrolytic refining, impure copper is connected to the positive side and pure copper to the negative side. Electricity moves pure copper from the impure block to the pure plate, leaving dirt behind.

🎯 Exam Tip: Clearly identify the anode (impure copper), cathode (pure copper), and electrolyte (copper sulphate with dilute sulphuric acid) for full marks.

 

Question 19. What are the methods employed to make an alloy?
Answer: Alloys are mixtures of metals, or metals with non-metals, created to improve their properties. There are two main ways to make alloys:

1. By fusing metals together: This is the most common method. Different metals are melted and mixed together in their liquid state. When the mixture cools and solidifies, an alloy is formed. For example, brass is made by melting zinc and copper together.
2. By compressing finely divided metals: In this method, very small particles of different metals are pressed together under high pressure. This can also form an alloy, especially when the metals do not mix well when molten, or if they have very different melting points. An example is wood metal, which is a fusible alloy of lead, tin, bismuth, and cadmium powder.

Both methods aim to combine the beneficial properties of the constituent elements.
In simple words: Alloys are made by either melting different metals together and letting them cool, or by pressing very small pieces of metals together.

🎯 Exam Tip: Remember the two main methods: fusing (melting and mixing) and compressing (powder metallurgy), and provide a simple example for each if possible.

 

Question 20. Write the components of wood metal.
Answer: Wood metal is an alloy that is made up of lead, tin, bismuth, and cadmium. This alloy is known for its very low melting point, making it useful in safety devices and as a fusible link.
In simple words: Wood metal is an alloy made from lead, tin, bismuth, and cadmium.

🎯 Exam Tip: List all four components accurately for wood metal, as it's a specific, multi-component alloy.

 

Question 21. What are the uses of copper?
Answer: Copper is a versatile metal used for many purposes due to its excellent properties:

• It is widely used in manufacturing electric cables and other electric appliances because it is an excellent conductor of electricity.
• Copper is used for making utensils, containers, calorimeters, and coins due to its good heat conductivity and resistance to corrosion.
• It is used in electroplating to provide a protective or decorative coating on other metals.
• Copper is alloyed with gold and silver to make coins and jewelry, improving their hardness and durability.

These uses highlight copper's importance in various industries.
In simple words: Copper is used to make electrical wires, cooking pots, and coins. It is also used for electroplating and mixed with gold and silver for jewelry.

🎯 Exam Tip: When listing uses, connect them to copper's key properties like excellent electrical/heat conductivity and corrosion resistance.

 

Question 22. Give two non-ferrous aluminium alloys.
Answer: Two important non-ferrous aluminium alloys are:

• Duralumin: This alloy is composed of Aluminium (Al), Magnesium (Mg), Copper (Cu), and Manganese (Mn).
• Magnalium: This alloy is primarily made of Aluminium (Al) and Magnesium (Mg).

These alloys are valued for their strength, low density, and corrosion resistance, making them useful in aircraft construction and other lightweight applications.
In simple words: Duralumin (made of aluminium, magnesium, copper, manganese) and Magnalium (made of aluminium and magnesium) are two important non-ferrous aluminium alloys.

🎯 Exam Tip: Remember the main components of each alloy (Duralumin: Al, Mg, Cu, Mn; Magnalium: Al, Mg).

 

Question 23. How is rust formed?
Answer: Rust is formed when iron metal is exposed to moist air, which means both oxygen and water are present. Over time, the iron reacts with oxygen and water to form a layer of reddish-brown hydrated ferric oxide on its surface. This compound is commonly known as rust. The chemical equation for rust formation is:
\( 4\text{Fe} + 3\text{O}_2 + \text{xH}_2\text{O} \rightarrow 2\text{Fe}_2\text{O}_3.\text{xH}_2\text{O} \text{ (Rust)} \)
The 'x' in \( \text{xH}_2\text{O} \) indicates a variable amount of water molecules. This process gradually destroys the iron.
In simple words: Rust forms when iron is left in air that has moisture. The iron reacts with oxygen and water to make a reddish-brown substance called hydrated ferric oxide, which is rust.

🎯 Exam Tip: The two key conditions for rusting are the presence of oxygen and water (moisture). Remember the general formula of rust: hydrated ferric oxide.

 

Question 24. Why are the alloys prepared?
Answer: Alloys are prepared to improve the properties of pure metals, making them more suitable for specific uses. Here are some reasons:

1. To modify appearance and colour: Alloys can have different colors or a more attractive finish than pure metals.
2. To modify chemical activity: Alloying can make metals more resistant to corrosion or less reactive.
3. To lower the melting point: Some alloys have a much lower melting point than their individual components, useful for soldering or fusible links.
4. To increase hardness and tensile strength: Alloys are generally harder and stronger than pure metals, making them more durable.
5. To increase resistance to electricity: While some alloys are good conductors, others are made to increase electrical resistance for heating elements.

By combining elements, we can create materials with custom-tailored properties.
In simple words: Alloys are made to make metals better. They can change color, make them stronger, stop them from rusting, or make them melt at lower temperatures.

🎯 Exam Tip: Focus on how alloying enhances the properties of pure metals, making them more useful (e.g., strength, corrosion resistance, melting point changes).

 

Question 25. Define corrosion.
Answer: Corrosion is the gradual destruction or degradation of metals. This happens due to a chemical or electrochemical reaction between the metal surface and its surrounding environment. Common examples include the rusting of iron or the tarnishing of silver. This process slowly wears away the metal, reducing its strength and usefulness.
In simple words: Corrosion is when metals slowly get destroyed by reacting with things in the air or water around them, like rust on iron.

🎯 Exam Tip: Emphasize "gradual destruction" and "chemical or electrochemical reaction with the environment" in your definition.

 

Question 26. What are alloys? How are they prepared?
Answer: An alloy is a homogeneous mixture of a metal with one or more other metals, or with certain non-metals, that are fused (melted and mixed) together. Alloys are designed to have improved properties compared to their pure components.
Alloys are generally prepared in two main ways:

• By fusing the metals together: This is the most common method. The constituent metals are melted and thoroughly mixed in their molten state. Upon cooling and solidification, they form a uniform alloy. For example, brass is an alloy of zinc (solute) in copper (solvent), made by melting copper and zinc together.
• By compressing finely divided metals: In this method, powdered forms of different metals are mixed and then pressed together under high pressure, often followed by heating (sintering) to bond the particles. This method is useful for metals that do not mix well when molten or have very different melting points.

This deliberate combination enhances characteristics like strength, hardness, and corrosion resistance.
In simple words: Alloys are uniform mixtures of metals, or metals with non-metals. They are made by melting and mixing the elements together, or by pressing their powders together.

🎯 Exam Tip: Define alloys as homogeneous mixtures and describe both the fusion (melting) and compression methods of preparation.

 

Question 27. Which is known as Wet corrosion or Electrochemical corrosion?
Answer: Wet corrosion is also known as electrochemical corrosion. This type of corrosion happens when a metal is exposed to moisture (water) and other substances like salts, acids, or bases, leading to an electrochemical reaction. It involves the formation of tiny anodic and cathodic areas on the metal surface, causing the metal to dissolve at the anode and reduction reactions (like oxygen reduction) at the cathode. This process is very common and responsible for significant material damage.
In simple words: Wet corrosion is also called electrochemical corrosion. It happens when metal reacts with water, acids, or salts, causing the metal to break down through tiny electrical reactions.

🎯 Exam Tip: Connect "wet corrosion" directly to "electrochemical reaction" and the presence of an aqueous medium (moisture, salts, acids, bases).

 

Question 28. Write a note on Cathodic protection.
Answer: Cathodic protection is a method used to control corrosion on a metal surface. It works by making the metal surface a cathode of an electrochemical cell, which prevents it from corroding. This is often done by connecting the metal to be protected to a more easily corrodible (more reactive) metal, called a "sacrificial metal." The sacrificial metal acts as the anode and corrodes instead of the main metal, thereby protecting it. For example, zinc can be used to protect iron pipelines.
In simple words: Cathodic protection stops metals from rusting by making them the negative pole in a small electric setup. A more active metal (sacrificial metal) rusts instead, protecting the main metal.

🎯 Exam Tip: The core idea of cathodic protection is making the metal "cathodic" and using a "sacrificial anode" that corrodes instead.

 

Question 29. What are the methods used to prevent corrosion?
Answer: Corrosion of metals can be prevented by several methods:

• By coating with paints: Painting metal surfaces creates a barrier that prevents contact with moisture and oxygen.
• By the process of galvanization: This involves coating iron or steel with a thin layer of zinc. Zinc is more reactive and corrodes preferentially, protecting the iron.
• By electroplating: A layer of a less reactive metal (like chromium, nickel, or tin) is deposited onto the surface of another metal using an electric current.
• By sacrificial protection: Connecting a more reactive metal (e.g., magnesium or zinc) to the metal to be protected. The more reactive metal corrodes first.
• By alloying with other metals: Creating alloys (like stainless steel) that are more corrosion-resistant than the pure metals.

These methods aim to either create a barrier or modify the metal's electrochemical properties.
In simple words: Corrosion can be stopped by painting, galvanizing (zinc coating), electroplating, using a sacrificial metal, or mixing metals to make alloys.

🎯 Exam Tip: When listing methods, briefly explain the mechanism (e.g., barrier, sacrificial anode) for each to show understanding.

 

Question 30. A reddish brown metal 'A' reacts with dil.HCl in the presence of O2 and forms the compound 'B'. 'B' can also be prepared by heating the metal A with Cl2. Identify A and B.
Answer:The reddish-brown metal 'A' is copper (Cu).
(A) Copper reacts with dilute hydrochloric acid (\( \text{HCl} \)) in the presence of oxygen (\( \text{O}_2 \)) to form copper(II) chloride (\( \text{CuCl}_2 \)), which is compound 'B'.
\( 2\text{Cu} + 4\text{HCl} + \text{O}_2 \rightarrow 2\text{CuCl}_2 \text{ (B)} + 2\text{H}_2\text{O} \)
(B) Copper(II) chloride (\( \text{CuCl}_2 \)) can also be prepared by directly heating metal A (Copper) with chlorine gas (\( \text{Cl}_2 \)).
\( \text{Cu} + \text{Cl}_2 \rightarrow \text{CuCl}_2 \)
Therefore, A is Copper (Cu) and B is Copper(II) chloride (\( \text{CuCl}_2 \)).
In simple words: Metal 'A' is copper, a reddish-brown metal. When it reacts with acid and oxygen, or directly with chlorine gas, it forms compound 'B', which is copper(II) chloride.

🎯 Exam Tip: Look for characteristic colors and common reactions for identification. Copper's reddish-brown color and its reaction with dilute HCl in the presence of oxygen are key clues.

 

Question 31. Write the uses of copper.
Answer: Copper is a very useful metal due to its excellent conductivity and corrosion resistance. Its main uses include:

1. It is widely used in manufacturing electric cables and other electric appliances because it is an excellent conductor of electricity.
2. It is used for making utensils, containers, calorimeters, and coins due to its good thermal conductivity and durability.
3. It is used in electroplating to provide a protective or decorative layer on other metals.
4. It is alloyed with gold and silver to make coins and jewels, as it increases their hardness and strength.

Copper is a crucial material in many industries.
In simple words: Copper is used for making electric wires, kitchen items, coins, and jewelry. It's also used for electroplating other metals.

🎯 Exam Tip: Focus on copper's properties (conductivity, malleability, corrosion resistance) as they directly link to its common uses.

 

Question 32. Write the name and formula of the ores of iron.
Answer: The important ores of iron and their chemical formulas are:

These are the primary sources from which iron is extracted.
In simple words: Common iron ores are haematite (\( \text{Fe}_2\text{O}_3 \)), magnetite (\( \text{Fe}_3\text{O}_4 \)), and iron pyrite (\( \text{FeS}_2 \)).

🎯 Exam Tip: Make sure to correctly write both the name and the chemical formula for each ore. Haematite and magnetite are the most common iron ores.

 

Question 33. Define periodicity.
Answer: Periodicity refers to the repeating patterns of physical and chemical properties of elements when they are arranged in the periodic table according to their atomic number. This recurrence happens at regular intervals, which is explained by the elements having similar outer electronic configurations. For example, elements in the same group often exhibit similar chemical behaviors. Anything that repeats itself after a fixed time or interval shows periodicity.
In simple words: Periodicity means that properties of elements repeat in a pattern when you look at them in the periodic table. This happens because their outer electron arrangements are similar.

🎯 Exam Tip: The key idea of periodicity is "repeating patterns" of "properties" related to "electronic configuration" at "regular intervals" in the periodic table.

 

Question 34. What happens in the combustion zone during the extraction of iron.
Answer: In the combustion zone of a blast furnace, which is the lowest part, very high temperatures of around \( 1500^{\circ}\text{C} \) are maintained. Here, coke (carbon) burns rapidly in the hot blast of air that is introduced into the furnace. This reaction produces carbon dioxide (\( \text{CO}_2 \)) and releases a large amount of heat, which is essential for the entire process.
\( \text{C} + \text{O}_2 \xrightarrow{1500^{\circ}\text{C}} \text{CO}_2 + \text{heat} \)
The limestone also decomposes in this hot region to calcium oxide (\( \text{CaO} \)) and carbon dioxide (\( \text{CO}_2 \)), and these reactions absorb heat (endothermic).
\( \text{CaCO}_3 \xrightarrow{\Delta} \text{CaO} + \text{CO}_2 \)
The calcium oxide then reacts with silica (\( \text{SiO}_2 \)) impurities to form calcium silicate slag. This slag is crucial for removing impurities from the molten iron.
In simple words: In the combustion zone of an iron furnace, coke burns with hot air at \( 1500^{\circ}\text{C} \) to make carbon dioxide and lots of heat. Limestone also breaks down here.

🎯 Exam Tip: Remember the two main reactions: carbon burning to form \( \text{CO}_2 \) (exothermic) and limestone decomposition (endothermic), which provides calcium oxide for slag formation.

 

Question 35. Explain the reactions taking place in the reduction zone.
Answer: In the upper region of the reduction zone within a blast furnace, the temperature is around \( 400^{\circ}\text{C} \). In this area, carbon monoxide (\( \text{CO} \)), which is formed in lower, hotter zones, acts as the primary reducing agent. It reacts with ferric oxide (\( \text{Fe}_2\text{O}_3 \)) from the iron ore, reducing it to spongy iron metal. This is the first step in converting the iron ore into usable iron.
\( \text{Fe}_2\text{O}_3 + 3\text{CO} \xrightarrow{400^{\circ}\text{C}} 2\text{Fe} \text{ (Pig iron)} + 3\text{CO}_2 \)
This reaction is crucial for iron extraction, gradually transforming the ore into metal before it reaches the hotter zones.
In simple words: In the reduction zone, carbon monoxide reacts with iron oxide at about \( 400^{\circ}\text{C} \). This turns the iron oxide into spongy iron.

🎯 Exam Tip: Identify carbon monoxide (\( \text{CO} \)) as the reducing agent and ferric oxide (\( \text{Fe}_2\text{O}_3 \)) as the substance being reduced to iron at around \( 400^{\circ}\text{C} \).

 

Question 36. Define Metallic radius
Answer: The metallic radius is defined as half the distance between the nuclei of two adjacent metal atoms in a metallic crystal lattice. Unlike covalent or ionic radii, metallic radius specifically applies to metals where atoms are held together by a metallic bond, forming a continuous structure. This value helps in understanding the packing and properties of metals.
In simple words: Metallic radius is half the distance between the centers of two metal atoms that are next to each other in a solid metal.

🎯 Exam Tip: Clearly state "half the distance" and "nuclei of adjacent metal atoms" in a "metallic crystal" for a precise definition.

 

Question 37. Complete the following reactions.
1. \( 4\text{Fe} + 10\text{HNO}_3 \rightarrow 4\text{Fe(NO}_3\text{)}_2 + \text{......} + 3\text{H}_2\text{O} \)
2. \( 2\text{Fe} + 6\text{H}_2\text{SO}_4 \rightarrow \text{Fe}_2\text{(SO}_4\text{)}_3 + \text{......} + 6\text{H}_2\text{O} \)
Answer: The complete reactions are:
1. \( 4\text{Fe} + 10\text{HNO}_3 \rightarrow 4\text{Fe(NO}_3\text{)}_2 + \text{NH}_4\text{NO}_3 + 3\text{H}_2\text{O} \)
2. \( 2\text{Fe} + 6\text{H}_2\text{SO}_4 \rightarrow \text{Fe}_2\text{(SO}_4\text{)}_3 + 3\text{SO}_2 + 6\text{H}_2\text{O} \) (when hot, concentrated sulphuric acid reacts with iron)
These reactions show iron's reactivity with different acids, producing various nitrogen or sulfur compounds.
In simple words: The first reaction of iron with nitric acid forms iron nitrate and ammonium nitrate. The second reaction with sulfuric acid forms iron sulfate and sulfur dioxide.

🎯 Exam Tip: Balancing redox reactions is crucial. Pay attention to the oxidation states of nitrogen and sulfur to identify the correct products.

 

Question 38. What happens when steam is passed over red hot iron?
Answer: When steam is passed over red hot iron, a magnetic oxide of iron, specifically triiron tetraoxide (\( \text{Fe}_3\text{O}_4 \)), is formed. In this reaction, iron is oxidized by the steam, and hydrogen gas is released. This process is used to create a protective magnetic oxide layer on iron.
\( 3\text{Fe} + 4\text{H}_2\text{O (steam)} \rightarrow \text{Fe}_3\text{O}_4 + 4\text{H}_2\uparrow \)
In simple words: When steam passes over very hot iron, it forms a magnetic iron oxide and hydrogen gas.

🎯 Exam Tip: Remember the product is magnetic iron oxide (\( \text{Fe}_3\text{O}_4 \)) and hydrogen gas, and that the iron must be red hot.

 

Question 39. Define Electron affinity.
Answer: Electron affinity is the amount of energy released when a gaseous atom gains an electron to form its anion (a negatively charged ion). This process often releases energy (exothermic), indicating the atom's attraction for electrons. It is typically measured in kilojoules per mole (\( \text{kJ} \text{ / mol} \)). High electron affinity means the atom strongly attracts electrons.
In simple words: Electron affinity is the energy released when a gas atom takes in an electron to become a negative ion.

🎯 Exam Tip: Key phrases are "energy released," "gaseous atom," "gains an electron," and "forms an anion."

 

Question 40. Complete the table.
Answer: Here is the completed table showing the trends of periodic properties in periods and groups:

These trends are fundamental to understanding how elements behave chemically.
In simple words: Atomic radius decreases across a period and increases down a group. Ionization energy, electron affinity, and electronegativity all increase across a period but decrease down a group.

🎯 Exam Tip: Memorize the trends for these four key periodic properties in both periods and groups, as they are frequently tested.

 

Question 41. Define Metallurgy.
Answer: Metallurgy is the scientific and engineering discipline concerned with extracting metals from their ores, purifying them, and then preparing them for various uses. This field also involves studying the physical and chemical properties of metals, as well as their structural arrangement of atoms, to develop new alloys and materials. From mining to final product, metallurgy covers the entire lifecycle of metals.
In simple words: Metallurgy is the science of getting metals from their ores, making them pure, and shaping them for different uses based on their properties.

🎯 Exam Tip: The definition of metallurgy should include extraction, purification, and modification of metals for specific applications.

 

Question 42. Write a short note on leaching or chemical process.
Answer: Leaching, also known as the chemical process, is a method used for concentrating ores, especially when the ore is in a very pure or fine form. In this method, the finely ground ore is treated with a suitable chemical reagent (a solvent). This reagent selectively dissolves the valuable ore while leaving the impurities (gangue) undissolved. The solution containing the dissolved ore is then separated from the solid impurities by filtration. Finally, the metal or its compound is recovered from this solution, often by precipitation using another suitable reagent. Bauxite (\( \text{Al}_2\text{O}_3.2\text{H}_2\text{O} \)), the ore of aluminium, is typically concentrated by leaching.
In simple words: Leaching is a chemical process where a special liquid dissolves the useful ore but leaves the dirt behind. The dissolved ore is then separated and recovered.

🎯 Exam Tip: Focus on the selectivity of the solvent: it dissolves the ore but not the impurities, followed by separation and recovery.

 

Question 43. Relate all the four columns of the table with their unique properties.
Answer: The table describes various metals, their specific ores, the chemical formulas of those ores, and a unique property or method of extraction associated with each metal. This showcases how the type of ore and its properties dictate the metallurgical process used to obtain the metal and how the metal's properties relate to its use. For example:

This table likely provides examples where each row represents a metal, its specific ore (which might be misaligned in the source), its chemical formula, and a key process or property. The relationship is that a metal is typically extracted from a specific ore, which has a distinct chemical composition, and this ore then undergoes a particular process (like froth flotation, blast furnace, Hall's process, or smelting) to yield the pure metal. Each metal and its associated processes have unique characteristics that differentiate them. (Note: The provided table in the source has mismatched rows for Metal, Ore, Formula, and Properties; the corrected table reflects common knowledge for these entries)
In simple words: The table connects each metal to its specific ore, the ore's chemical makeup, and the main way that metal is processed or a special thing it does. Each metal, its ore, its formula, and its use or extraction method are unique to it.

🎯 Exam Tip: Pay close attention to matching the correct metal with its ore, formula, and the appropriate extraction method. This requires understanding different metallurgical processes for various metals.

 

Question 44. Guess Who I am?
(i) I am preserved in Kerosene.
(ii) My ore is leached with NaOH.
(iii) I sacrifice myself to protect my friend Iron.
(iv) I am being used in propellers
Answer:
(i) I am preserved in Kerosene. - Sodium
(ii) My ore is leached with \( \text{NaOH} \). - Aluminium
(iii) I sacrifice myself to protect my friend Iron. - Magnesium / Zinc (used in sacrificial protection)
(iv) I am being used in propellers - Nickel steel / Aluminium alloys
This question tests knowledge of various metal properties and uses.
In simple words: (i) Sodium is kept in kerosene. (ii) Aluminium's ore is treated with NaOH. (iii) Magnesium or Zinc protects iron by corroding itself. (iv) Nickel steel or aluminium alloys are used for propellers.

🎯 Exam Tip: For "Guess Who I am?" questions, think about unique properties or specific uses of metals that clearly distinguish them.

 

Question 45. Explain the method of making alloys.
Answer: Alloys are mixtures of metals (or a metal and a non-metal) that are prepared to enhance their properties for specific applications. There are two primary methods for making alloys:

• By fusing the metals together: This is the most common method. The different metals are heated until they melt and become liquid. They are then mixed thoroughly while in the molten state. As this mixture cools and solidifies, it forms a homogeneous alloy. For example, brass is made by melting zinc and copper together.
• By compressing finely divided metals: In this method, very fine powders of the constituent metals are mixed together. This mixture is then pressed under high pressure, sometimes with subsequent heating (sintering), to form a solid alloy. This technique is often used when metals have very different melting points or do not easily mix when molten, as seen with wood metal (an alloy of lead, tin, bismuth, and cadmium powder).

These methods allow for the creation of materials with custom properties like increased strength, corrosion resistance, or modified melting points.
In simple words: Alloys are made by either melting different metals and mixing them, or by pressing together fine powders of metals.

🎯 Exam Tip: Clearly describe both the "fusion" (melting) and "compression" (powder metallurgy) methods, providing an example for each if possible.

 

Question 46. Write the differences between a mineral and a ore.
Answer: Here are the key differences between a mineral and an ore:

This distinction is important in geology and metallurgy. For example, aluminium is present in many minerals, but bauxite is its main ore because it's the most profitable to extract from.
In simple words: Minerals are natural solid materials found in the Earth. Ores are special minerals from which we can get metals easily and profitably. So, every ore is a mineral, but not every mineral is an ore.

🎯 Exam Tip: The core difference is economic viability: an ore must be profitable to extract metal from, while a mineral just contains the metal without this condition.

 

Question 1. Write the reactions taking place during Bessemerisation of copper.
Answer: Bessemerisation is a process used in the extraction of copper to convert copper matte (a mixture of \( \text{Cu}_2\text{S} \) and \( \text{FeS} \)) into blister copper. Air is blown through the molten matte, leading to several reactions:
First, iron sulfide reacts with oxygen to form iron(II) oxide and sulfur dioxide:
\( 2\text{FeS} + 3\text{O}_2 \rightarrow 2\text{FeO} + 2\text{SO}_2\uparrow \)
The iron(II) oxide then combines with silica (\( \text{SiO}_2 \)) (added as flux) to form iron silicate, which is slag:
\( \text{FeO} + \text{SiO}_2 \rightarrow \text{FeSiO}_3\downarrow \text{ (slag)} \)
Next, copper(I) sulfide reacts with oxygen to form copper(I) oxide and sulfur dioxide:
\( 2\text{Cu}_2\text{S} + 3\text{O}_2 \rightarrow 2\text{Cu}_2\text{O} + 2\text{SO}_2\uparrow \)
Finally, the copper(I) oxide reacts with any remaining copper(I) sulfide to produce molten copper and sulfur dioxide gas:
\( 2\text{Cu}_2\text{O} + \text{Cu}_2\text{S} \rightarrow 6\text{Cu} + \text{SO}_2\uparrow \)
The sulfur dioxide gas escaping from the solidifying copper creates blisters, giving the product its name, blister copper. This process is crucial for removing impurities and obtaining nearly pure copper.
In simple words: During Bessemerisation, air is blown into molten copper matte. Iron sulfide reacts to form slag, and then copper sulfide reacts to make copper metal. Sulfur dioxide gas is released, leaving blister copper.

🎯 Exam Tip: Ensure you include all key reactions: oxidation of FeS, slag formation with \( \text{SiO}_2 \), oxidation of \( \text{Cu}_2\text{S} \), and the final reduction of \( \text{Cu}_2\text{O} \) by \( \text{Cu}_2\text{S} \).

 

Question 2. How do electronegativity values help to find out the nature of bonding between atoms?
Answer: Electronegativity values are very useful in determining the nature of the chemical bond between two atoms. The difference in electronegativity between the bonded atoms helps predict whether the bond will be ionic, covalent, or somewhere in between:

• If the difference in electronegativity between two elements is exactly 1.7, the bond is considered to have 50% ionic character and 50% covalent character.
• If the difference is less than 1.7, the bond is primarily considered to be covalent. The smaller the difference, the more non-polar the covalent bond.
• If the difference is greater than 1.7, the bond is primarily considered to be ionic. A larger difference means a more ionic character, where one atom essentially transfers an electron to the other.

This scale provides a good guide for predicting bond type, though it's a generalization.
In simple words: The difference in electronegativity between two atoms tells us what kind of bond they will form. A difference less than 1.7 usually means a covalent bond, and a difference more than 1.7 means an ionic bond. A difference of 1.7 means it's half ionic, half covalent.

🎯 Exam Tip: Remember the critical electronegativity difference value of 1.7 and what it signifies (50% ionic/covalent character). State clearly how differences above or below this value indicate ionic or covalent bonds, respectively.

 

Question 3. Explain Froth floatation with diagram.
Answer: The Froth Flotation process is a method used to concentrate lighter ore particles, particularly sulfide ores, by separating them from gangue (impurities).
Principle: This process relies on the preferential wettability of the ore particles by oil (like pine oil) and the gangue particles by water. Ore particles are hydrophobic (water-repelling) and prefer to stick to oil and air bubbles, while gangue particles are hydrophilic (water-attracting) and remain wetted by water.
Process: The finely crushed ore is mixed with water, a frothing agent (e.g., pine oil), and a collector (e.g., potassium ethyl xanthate). Air is then blown into the mixture. The frothing agent creates stable bubbles. The collector selectively coats the ore particles, making them water-repellent. As air bubbles rise, the oil-coated ore particles attach to them and are carried to the surface, forming a froth. The froth, containing the concentrated ore, is skimmed off, while the gangue settles at the bottom. For example, zinc blende (\( \text{ZnS} \)) is concentrated by this method.

In simple words: Froth flotation uses oil to make ore particles stick to air bubbles. The bubbles float up, carrying the ore with them as froth, while the unwanted dirt sinks in the water.

🎯 Exam Tip: Crucial elements for this answer are the principle of differential wettability, the roles of frothing agents and collectors, and illustrating the separation process clearly.

 

Question 4. Explain the Baeyer's process of conversion of Bauxite into alumina.
Answer: Baeyer's process is a chemical method used to purify bauxite ore (\( \text{Al}_2\text{O}_3.2\text{H}_2\text{O} \)) and convert it into pure alumina (\( \text{Al}_2\text{O}_3 \)), which is then used to extract aluminium.
(i) Digestion: First, the finely ground bauxite ore is mixed with a concentrated solution of caustic soda (sodium hydroxide, \( \text{NaOH} \)). This mixture is heated under pressure to about \( 150^{\circ}\text{C} \). Under these conditions, the alumina in the bauxite dissolves to form soluble sodium meta aluminate (\( \text{NaAlO}_2 \)), while impurities like iron oxides remain undissolved.
\( \text{Al}_2\text{O}_3.2\text{H}_2\text{O} + 2\text{NaOH} \rightarrow 2\text{NaAlO}_2 + 3\text{H}_2\text{O} \)
(ii) Dilution and Precipitation: The sodium meta aluminate solution is then diluted with water and cooled. A small amount of freshly prepared aluminium hydroxide (\( \text{Al(OH)}_3 \)) is added as a seed crystal. This causes the aluminium hydroxide to precipitate out from the solution.
\( \text{NaAlO}_2 + 2\text{H}_2\text{O} \rightarrow \text{Al(OH)}_3\downarrow + \text{NaOH} \)
(iii) Calcination: The precipitated aluminium hydroxide is filtered, washed, and then dried. Finally, it is strongly heated (ignited) at a high temperature, typically around \( 1000^{\circ}\text{C} \). This process, called calcination, removes water molecules, leaving behind pure anhydrous alumina.
\( 2\text{Al(OH)}_3 \xrightarrow{1000^{\circ}\text{C}} \text{Al}_2\text{O}_3 + 3\text{H}_2\text{O} \)
This pure alumina is then used in the Hall's process for the electrolytic reduction to aluminium metal.
In simple words: Baeyer's process purifies bauxite to alumina. First, bauxite is dissolved in hot caustic soda to form sodium aluminate. Then, aluminium hydroxide is made to fall out of the solution. Lastly, this hydroxide is heated strongly to become pure alumina powder.

🎯 Exam Tip: Break down the Baeyer's process into three main steps: digestion (forming soluble sodium aluminate), precipitation (forming aluminium hydroxide), and calcination (forming pure alumina), and include the key reagents and temperatures for each step.

 

Question 5. Explain the Hall's Process of electrolytic reduction of alumina with diagram.
Answer: Hall's process is a method used to make aluminium. It works by using electricity to separate pure aluminium from alumina, which is aluminium oxide. The process takes place in a special cell where alumina is melted and mixed with cryolite and fluorspar to help it melt at a lower temperature. An electric current is then passed through this mixture. The pure aluminium collects at the bottom (cathode), while oxygen gas is released at the graphite anodes. This method is crucial for industrial aluminium production.
\( 2 \text{Al}_2\text{O}_3 \rightarrow 4 \text{Al} + 3\text{O}_2 \uparrow \)
In simple words: Hall's process uses electricity to get pure aluminium from aluminium oxide. The melted mixture is put in a tank, and electricity pulls the aluminium out.

🎯 Exam Tip: When drawing diagrams for processes, label each major component clearly and accurately to demonstrate full understanding.

 

Question 6. Write the reaction involved in the middle region of blast furnace during the extraction of iron.
Answer: In the middle area of a blast furnace, the temperature is around \( 1000^\circ\text{C} \). Here, carbon dioxide from the combustion zone reacts with carbon (coke) to form carbon monoxide. This carbon monoxide is a very important reducing agent needed for further reactions in the furnace.
\( \text{CO}_2 + \text{C} \xrightarrow{1000^\circ\text{C}} 2\text{CO} - \text{Heat} \)
In simple words: In the middle of the furnace, hot carbon dioxide changes into carbon monoxide when it meets more carbon.

🎯 Exam Tip: Remember that carbon monoxide (CO) is the key reducing agent in the blast furnace for iron extraction.

 

Question 7. What are the three different types of iron? Write their uses.
Answer: The three main types of iron, classified by their carbon content, are:
(i) Pig iron: This type of iron has a high carbon content, between 2% and 4.5%. It is commonly used to make things like pipes, stoves, radiators, railings, manhole covers, and drainage pipes.
(ii) Steel: Steel contains less than 0.25% carbon. It is a versatile material used in building construction, machinery, transmission cables, TV towers, and for making various alloys.
(iii) Wrought iron: Wrought iron has a carbon content ranging from 0.25% to 2%. It is primarily used to make strong items such as springs, anchors, and electromagnets. These different carbon percentages give each iron type unique properties.
In simple words: There are three main kinds of iron: pig iron for heavy cast things, steel for buildings and machines, and wrought iron for strong tools like springs. Each has a different amount of carbon inside.

🎯 Exam Tip: Understanding the carbon content for each type of iron helps to explain its specific properties and applications.

 

Question 8. What is corrosion? Write the chemistry behind the formation of rust.
Answer: Corrosion is the slow wearing away of a metal. This happens when the metal reacts with chemicals in its surroundings, often due to an electrochemical process. For iron, this process is called rusting.
When iron is left exposed to moist air, its surface forms a reddish-brown layer. This layer is hydrated ferric oxide, which we call rust. The process starts when iron loses electrons to become ferrous ions (\( \text{Fe}^{2+} \)). Oxygen and water then gain electrons to form hydroxide ions (\( \text{OH}^- \)). These ferrous ions are further oxidized to ferric ions (\( \text{Fe}^{3+} \)). Finally, the ferric ions combine with hydroxide ions to form iron(III) hydroxide (\( \text{Fe(OH)}_3 \)), which then dehydrates to become the hydrated ferric oxide (\( \text{Fe}_2\text{O}_3\cdot\text{xH}_2\text{O} \)) that is commonly known as rust.
\( \text{Fe} \rightarrow \text{Fe}^{2+} + 2\text{e}^- \)
\( \text{O}_2 + 2\text{H}_2\text{O} + 4\text{e}^- \rightarrow 4\text{OH}^- \)
\( \text{O}_2 + 4\text{H}^+ + 4\text{e}^- \rightarrow 2\text{H}_2\text{O} \)
\( \text{Fe}^{3+} + \text{OH}^- \rightarrow \text{Fe(OH)}_3 \) (then dehydrates) \( \implies \text{Fe}_2\text{O}_3\cdot\text{xH}_2\text{O} \) (Rust)
In simple words: Corrosion is when metals slowly get destroyed by reacting with their environment. Rusting is when iron reacts with air and water, turning into a flaky reddish-brown material called rust.

🎯 Exam Tip: Remember that both oxygen and moisture are necessary for iron to rust, and impurities often speed up the process.

 

Question 9. Explain the methods of preventing corrosion.
Answer: Metals can be protected from corrosion using several methods:
(i) Alloying: Mixing metals together to create an alloy can make them more resistant to corrosion. For example, stainless steel, an alloy of iron with other elements, is very resistant to rust.
(ii) Surface Coating: This involves putting a protective layer on the metal's surface. There are different ways to do this:
(a) Galvanization: This is when a layer of zinc is applied to iron using an electric current. Zinc protects the iron even if the layer is scratched.
(b) Electroplating: This method uses an electric current to cover one metal with a thin layer of another metal. This not only protects the metal but can also make it look better.
(c) Anodizing: This electrochemical process makes the metal surface harder, more durable, and more resistant to corrosion. Aluminium is often anodized for protection and decorative purposes.
(d) Cathodic Protection: In this method, a metal that corrodes more easily (a sacrificial metal) is connected to the metal being protected. The sacrificial metal corrodes instead of the main metal, keeping the main metal safe.
In simple words: We can stop metals from rusting or corroding by mixing them with other metals (making alloys), painting them, coating them with zinc (galvanizing), covering them with another metal using electricity (electroplating), making their surface tough (anodizing), or by using a "sacrificial" metal that rusts instead of the important one.

🎯 Exam Tip: When describing corrosion prevention methods, always mention both the technique and the underlying principle (e.g., sacrificial protection in galvanization).

 

Question 10. Discuss the main features of Periods in the modern periodic table (or) long form of periodic table.
Answer: In the modern periodic table, periods are the horizontal rows of elements. There are seven periods in total, and each one shows a trend in the properties of elements as you move from left to right.
1. First period (Atomic number 1 and 2): This is the shortest period, containing only two elements: Hydrogen and Helium.
2. Second period (Atomic number 3 to 10): This is a short period with eight elements, from Lithium to Neon.
3. Third period (Atomic number 11 to 18): This is also a short period with eight elements, from Sodium to Argon.
4. Fourth period (Atomic number 19 to 36): This is a long period with eighteen elements, from Potassium to Krypton. It includes 8 regular elements and 10 transition elements.
5. Fifth period (Atomic number 37 to 54): This is another long period with eighteen elements, from Rubidium to Xenon. Like the fourth period, it has 8 regular elements and 10 transition elements.
6. Sixth period (Atomic number 55 to 86): This is the longest period, containing 32 elements, from Caesium to Radon. It includes 8 regular elements, 10 transition elements, and 14 inner transition elements (the Lanthanides).
7. Seventh period (Atomic number 87 to 118): This period is similar to the sixth, also accommodating 32 elements. Recently, four new elements have been officially included by IUPAC.
In simple words: Periods are the rows in the periodic table. There are seven rows, and they vary in length. Each row groups elements with similar electron shell structures, and element properties change gradually as you move across.

🎯 Exam Tip: Remember that elements in the same period have the same number of electron shells, which influences their properties.

 

Question 11. Discuss the main feature of Groups in the long form of periodic table.
Answer: In the long form of the periodic table, groups are the vertical columns. These groups organize elements that have similar chemical properties.
(i) The vertical columns, running from top to bottom in the periodic table, are called groups. There are 18 groups in total.
(ii) Elements within each group share common characteristics, which is why they are often grouped into different families (like the Alkali Metals or Halogens).
(iii) The Lanthanides and Actinides are special sets of elements that are part of Group 3 but are shown separately to keep the table compact. They are known as inner transition elements.
(iv) Except for Group 0 (noble gases), all elements in a group have the same number of electrons in their outermost shell, also known as their valence shell. This similarity in valence electrons gives them the same valency. For example, all elements in Group 1 have one electron in their valence shell (like \( 1s^1 \)) and a valency of '1'.
(v) Because elements in a group have identical electron configurations in their outermost shells, they show similar chemical properties.
(vi) The physical properties of elements within a group, such as their melting point, boiling point, and density, change in a smooth, gradual way as you move down the group.
(vii) The atoms of 'group 0' elements, known as noble gases, have a very stable electron configuration in their valence shells. This makes them very unreactive.
In simple words: Groups are the columns in the periodic table. Elements in the same group have similar chemical behaviors because they have the same number of electrons in their outer shell. Physical properties change in a steady way from top to bottom.

🎯 Exam Tip: A good understanding of group classifications helps predict chemical behavior and reactivity of elements.

 

Question 1. Why noble gases have zero electron affinity value?
Answer: Noble gases have a zero electron affinity value because their outermost electron shells are completely full and very stable. This means they do not want to gain any more electrons. Because their electron orbitals are already filled, there is no empty space for new electrons to join, so they show no tendency to accept electrons.
In simple words: Noble gases don't take on new electrons because their outer electron shells are already full and happy, making them very stable.

🎯 Exam Tip: Recognize that a full valence shell is a key characteristic of noble gases, leading to their chemical inertness and zero electron affinity.

 

Question 2. Arrange the following ions in order of their increasing ionic radii: Li+, Mg2+, K+ Al3+
Answer: The ions arranged in order of their increasing ionic radii are:
\( \text{Al}^{3+} < \text{Li}^+ < \text{Mg}^{2+} < \text{K}^+ \)
When comparing ions, factors like nuclear charge and the number of electron shells determine their size. For ions with the same number of electrons (isoelectronic species), the size decreases as the positive charge increases because the electrons are pulled closer to the nucleus.
In simple words: Starting from the smallest, the ions are aluminium 3+, then lithium +, then magnesium 2+, and the largest is potassium +.

🎯 Exam Tip: Remember that for isoelectronic ions, the more positive the charge, the smaller the ionic radius due to stronger pull from the nucleus.

 

Question 3. Cationic radius is smaller than its corresponding neutral atom. Why?
Answer: A cationic radius is always smaller than the radius of its original neutral atom. This happens because when a neutral atom loses one or more electrons to form a cation, it loses its outermost electron shell, or the remaining electrons are pulled much closer to the nucleus. After losing electrons, the number of positive charges (protons) in the nucleus stays the same, but the number of negative charges (electrons) decreases. This means the nucleus can attract the remaining electrons more strongly, making the electron cloud shrink and the cation smaller than the neutral atom it came from.
In simple words: When an atom loses electrons to become a positive ion (cation), it gets smaller. This is because the nucleus can pull the fewer remaining electrons closer, and sometimes a whole electron shell is lost.

🎯 Exam Tip: Always explain that electron loss leads to a higher effective nuclear charge per electron, pulling the electron cloud inward and reducing the atomic size.