CBSE Class 10 Chemistry Metals and Non-metals MCQs Set 13

Answer: (d) Sulphur

Explanation:
1. Calcium, copper and potassium are metals.
2. Sulphur is a non-metal.

Teacher's Note:
1. Metals lose electrons easily, sulphur gains them.
2. Sulphur is a brittle yellow solid that does not conduct electricity.

Answer: (a) Iron

Explanation:
1. Haemoglobin in red blood cells carries oxygen and contains iron.
2. Iron is held in the haem part of the molecule.

Teacher's Note:
1. Iron deficiency causes anaemia.
2. Magnesium is present in chlorophyll.

Answer: (d) Lead

Explanation:
1. Silver is the best conductor of heat, followed by copper, gold and aluminium.
2. Lead (and mercury) are poor conductors of heat among metals.

Teacher's Note:
1. Lead and mercury are poor conductors among metals.
2. Silver is the best conductor of both heat and electricity.

Answer: (c) Silver

Explanation:
1. Silver has the highest electrical conductivity of all metals.
2. Copper is a close second and is used for wires because it is cheaper.

Teacher's Note:
1. Remember the order silver, copper, gold, aluminium.
2. Wires are made of copper or aluminium for cost reasons.

Answer: (b) Bromine

Explanation:
1. Bromine is the only non-metal that is liquid at room temperature.
2. Mercury is a liquid metal.

Teacher's Note:
1. At room temperature only mercury (metal) and bromine (non-metal) are liquids.
2. Silicon and sulphur are solids.

Answer: (c) Aluminium

Explanation:
1. Aluminium oxide reacts with both acids and bases to form salt and water.
2. So it is amphoteric.

Teacher's Note:
1. \( \ce{Al2O3} \) and \( \ce{ZnO} \) are common amphoteric oxides.
2. Copper, silver and iron oxides are basic.

Answer: (b) \( \ce{Na2ZnO2 + H2} \)

Explanation:
1. Zinc reacts with hot concentrated alkali to form sodium zincate and hydrogen gas.
2. \( \ce{Zn + 2NaOH -> Na2ZnO2 + H2} \).

Teacher's Note:
1. Zinc and aluminium react with both acids and bases.
2. The gas evolved is hydrogen.

Answer: (c) Carbon

Explanation:
1. Carbon dioxide is used by plants in photosynthesis.
2. The oxide \( \ce{CO2} \) has the form \( \ce{XO2} \) with X = carbon.

Teacher's Note:
1. \( \ce{SO2} \) is also of the form \( \ce{XO2} \) but is not used in photosynthesis.
2. Plants make glucose from \( \ce{CO2} \) and water.

Answer: (b) Sulphuric acid

Explanation:
1. \( \ce{SO3 + H2O -> H2SO4} \).
2. Sulphurous acid is formed from sulphur dioxide.

Teacher's Note:
1. Non-metal oxides dissolve in water to form acids.
2. \( \ce{SO2 + H2O -> H2SO3} \).

Answer: (d) Magnesium

Explanation:
1. Metals form basic oxides.
2. Magnesium gives MgO, a basic oxide.
3. Chlorine, sulphur and phosphorus are non-metals and give acidic oxides.

Teacher's Note:
1. Metal oxide is basic, non-metal oxide is acidic.
2. MgO turns red litmus blue in water.

Answer: (d) Aluminium

Explanation:
1. Aluminium forms a thin tough layer of \( \ce{Al2O3} \) which sticks to the surface and prevents further oxidation.

Teacher's Note:
1. Rust, by contrast, flakes off iron and exposes fresh metal.
2. Aluminium oxide layer can be thickened by anodising.

Answer: (a) Potassium

Explanation:
1. Potassium is very reactive and catches fire in air.
2. It is therefore stored under kerosene.

Teacher's Note:
1. Sodium and lithium are also stored under oil.
2. White phosphorus is stored under water.

Answer: (a) Calcium

Explanation:
1. A high melting point oxide soluble in water suggests an ionic oxide of an active metal.
2. Calcium forms CaO, which is ionic and reacts with water to form calcium hydroxide.
3. Carbon oxides are gases, \( \ce{SiO2} \) is insoluble and iron oxides are insoluble.

Teacher's Note:
1. Ionic compounds have high melting points.
2. Oxides of the most reactive metals dissolve in water to give alkalis.

Answer: (b) under water

Explanation:
1. White phosphorus catches fire in air at about 35 degrees C.
2. It is stored under water to keep air away.

Teacher's Note:
1. It is insoluble in water but soluble in carbon disulphide.
2. Sodium and potassium are stored under kerosene instead.

Answer: (b) Sodium

Explanation:
1. Sodium reacts vigorously with cold water to give sodium hydroxide and hydrogen.
2. Zinc reacts only with steam, and mercury and tungsten do not react.

Teacher's Note:
1. Highly reactive metals like K, Na and Ca react with cold water.
2. Mg reacts with hot water.

Answer: (d) ZnO and \( \ce{H2} \)

Explanation:
1. Zinc reacts with steam to form zinc oxide and hydrogen.
2. \( \ce{Zn + H2O -> ZnO + H2} \).

Teacher's Note:
1. Metals that do not react with water often react with steam.
2. Metal oxide plus hydrogen are the products.

Answer: (c) Na > Mg > Zn > Fe

Explanation:
1. In the reactivity series the order is Na > Mg > Zn > Fe.
2. Sodium reacts with cold water, magnesium with hot water and zinc and iron only with steam, zinc being more reactive than iron.

Teacher's Note:
1. Learn the series K, Na, Ca, Mg, Al, Zn, Fe, Pb, H, Cu, Hg, Ag, Au.
2. Reactivity decreases down the list.

Answer: (c) Ag

Explanation:
1. Metals above hydrogen in the reactivity series liberate hydrogen from dilute acids.
2. Silver is below hydrogen, so there is no reaction.

Teacher's Note:
1. Cu, Hg, Ag, Au do not react with dilute HCl.
2. K, Na and Zn all release hydrogen.

Answer: (a) only zinc reacts with dilute hydrochloric acid

Explanation:
1. Zinc is above hydrogen in the reactivity series, so it displaces hydrogen from HCl.
2. Copper is below hydrogen and does not react.

Teacher's Note:
1. Only metals above hydrogen release hydrogen from acids.
2. The copper stays behind unreacted.

Answer: (b) no reaction

Explanation:
1. Copper lies below hydrogen in the reactivity series.
2. It cannot displace hydrogen from dilute HCl, so there is no reaction.

Teacher's Note:
1. Copper reacts with oxidising acids like nitric acid, not with HCl.
2. Check position relative to hydrogen.

Answer: (c) Silver

Explanation:
1. A more reactive metal displaces copper from copper sulphate.
2. Al, Pb and Zn are more reactive than copper and would react.
3. Silver is less reactive, so it is safe.

Teacher's Note:
1. Copper sulphate attacks iron, zinc and aluminium containers.
2. A less reactive metal cannot displace copper.

Answer: (b) beaker B

Explanation:
1. Copper is more reactive than silver but less reactive than zinc and iron.
2. So only silver sulphate reacts: \( \ce{Cu + Ag2SO4 -> CuSO4 + 2Ag} \) forms a blue \( \ce{Cu^2+} \) solution and silver.
3. Beaker B shows the blue colour.

Teacher's Note:
1. A metal displaces only less reactive metals from their salt solutions.
2. Blue colour indicates \( \ce{Cu^2+} \) ions.

Answer: (c) copper sulphate

Explanation:
1. Iron is more reactive than copper but less reactive than zinc and aluminium.
2. Only in copper sulphate does iron displace a metal, depositing reddish-brown copper.

Teacher's Note:
1. Reddish-brown deposit means copper.
2. The blue solution fades to pale green.

Answer: (c) Mg, Mn

Explanation:
1. Nitric acid is a strong oxidising agent and normally oxidises the hydrogen formed to water.
2. Only magnesium and manganese give hydrogen with very dilute, cold nitric acid.

Teacher's Note:
1. Hydrogen is not usually evolved from nitric acid with metals.
2. Mg and Mn are the exceptions with very dilute acid.