Metal and Non-Metal, Chapter-3, Class 10, CBSE, NCERT Exemplar

Soln:

The answer is b)

Explanation:

Copper ions are dispersed from the positively charged anode and deposited on the negatively charged cathode.

Short Answer Questions

37. Iqbal treated a lustrous, divalent element M with sodium hydroxide. He observed the formation of bubbles in a reaction mixture. He made the same observations when this element was treated with hydrochloric acid. Suggest how can he identify the produced gas. Write chemical equations for both the reactions.

Soln:

To identify the produced gas, lighted matchstick should be brought near the gas. If match stick burns with a
“pop” sound, it indicates the evolution of Hydrogen gas.

M+ 2NaOH → Na2MO2+ H2

With HCl

M+ 2HCl →MCl2+H2

38. During the extraction of metals, electrolytic refining is used to obtain pure metals. 

(a) Which material will be used as anode and cathode for refining of silver metal by this process?
(b) Suggest a suitable electrolyte also. 

(c) In this electrolytic cell, where do we get pure silver after passing electric current?

Soln:

1. During extraction of metals, impure metal will be used as an anode, and pure metal is used as a cathode for refining of silver metal by this electrolytic refining.
2. Silver Sulphate or Silver Nitrate
3. Pure silver is obtained on the cathode

39. Why should the metal sulphides and carbonates be converted to metal oxides in the process of
extraction of metal from them?

Soln:

Metal sulphides and carbonates are converted to metal oxides in the process of extraction of metal from them because metals can be obtained easier in oxide form than its sulphide or carbonate form.

40. Generally, when metals are treated with mineral acids, hydrogen gas is liberated, but when metals (except Mn and Mg), treated with HNO3, hydrogen is not liberated, why?

Soln:

HNO3 is a strong oxidizing agent. It oxidises the liberated Hydrogen into the water while converting itself to nitrogen oxide.

41. Compound X and aluminium are used to join railway tracks. 

(a) Identify the compound X 

(b) Name the reaction 

(c) Write down its reaction.

Soln:

1. Answer is Fe2O3
2. The involved reaction is a thermite reaction which is also called as aluminothermy
3. Fe2O3(s) + 2Al(s)→ Al2O3 (s) + 2Fe(s) + Heat 

42. When a metal X is treated with cold water, it gives a basic salt Y with molecular formula XOH (Molecular mass = 40) and liberates a gas Z which easily catches fire. Identify X, Y and Z
and also write the reaction involved.

Soln:

X is Na because the molecular mass of NaOH is 40.

Hence Y is NaOH ; Z is hydrogen has which catches fire when reacts with water.

2Na+2H2O → 2NaOH+H2

43. A non-metal X exists in two different forms Y and Z. Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y and Z.

Soln:

X is Carbon, Y and Z are Diamond and Graphite, which are allotropes of the carbon.

44. The following reaction takes place when the aluminium powder is heated with MnO2

3 MnO2 (s) + 4 Al (s) → 3 Mn (l) + 2 Al2O3 (l) + Heat

(a) Is aluminium getting reduced?
(b) Is MnO2 getting oxidised?

Soln:

In this reaction, aluminium gets oxidized as oxygen gets combined with it. Since oxygen is removed from MnO2, it is getting reduced.

45. What are the constituents of solder alloy? Which property of solder makes it suitable for welding electrical wires?

Soln:

Solder alloy is made of Lead and aluminium. Its low melting point makes it suitable for welding electrical wires.

46. A metal A, which is used in thermite process, when heated with oxygen gives an oxide B, which is amphoteric in nature. Identify A and B. Write down the reactions of oxide B with HCl and NaOH.

Soln:

Metal A is Aluminium and B is Al2O3

With HCl

Al2O3+ 6HCl →2AlCl3+3H2O

With NaOH

Al2O3+2NaOH →2NaAlO2+H2O

47. A metal that exists as a liquid at room temperature is obtained by heating its sulphide in the presence of air. Identify the metal and its ore and give the reaction involved.

Soln:

Mercury is the metal which is liquid at room temperature. Ore of Mercury is Cinnabar. When we heat cinnabar in atmospheric oxygen following reaction takes place.

2HgS + 3O2→ 2HgO + 2SO2

Mercuric oxide is again heated to get Mercury and Oxygen

2HgO  → (on heating) Hg+O2

48. Give the formulae of the stable binary compounds that would be formed by the combination of the
following pairs of elements.

(a) Mg and N2

(b) Li and O2

(c) Al and Cl2

(d) K and O2

Soln:

1. Magnesium Nitride (Mg3N2)
2. Lithium Oxide( Li2O)
3. Aluminium Chloride( AlCl3)
4. Potassium Oxide ( K2O)

49. What happens when

(a) ZnCO3 is heated in the absence of oxygen?

(b) a mixture of Cu2O and Cu2S is heated?

Soln:

a) When ZnCO3 is heated in the absence of oxygen Zinc Oxide and Carbon-di-oxide are liberated.

ZnCo3 →ZnO + CO2

b) When a mixture of Cu2O and Cu2S is heated, we get pure copper

2 Cu2O+ Cu2S →6Cu+SO2

50. A non-metal A is an important constituent of our food and forms two oxides B and C. Oxide B is toxic whereas C causes global warming

(a) Identify A, B and C

(b) To which Group of Periodic Table does A belong?

Soln:

a) A is Carbon. B is Carbon monoxide and C is Carbon-dioxide

b) Group 14

51. Give two examples each: The metals that are good conductors and poor conductors of heat, respectively.

Soln:

Good conductors- Iron and Copper

Bad conductors- Lead and Mercury

52. Name one metal and one non-metal that exist in a liquid state at room temperature. Also, name two
metals having a melting point less than 310 K (37°C)

Soln:

Mercury and Bromine are liquid at room temperature. Caesium and Gallium are the metals whose melting point is less than 310K(37°c).

53. An element A reacts with water to form a compound B which is used in whitewashing. The compound B on heating forms an oxide C which on treatment with water gives back B. Identify A, B and C and give the reactions involved.

Soln:

A is calcium, B is calcium Hydroxide, and C is Calcium Oxide.

Ca+2H2O →Ca(OH)2+ H2

Ca(OH)2 →CaO+H2O

CaO+H2O→ Ca(OH)2

54. An alkali metal A gives a compound B (molecular mass = 40) on reacting with water. The compound B gives a soluble compound C on treatment with aluminium oxide. Identify A, B and C and give the reaction involved.

Soln:

A is sodium and B is Sodium Hydroxide. Because the molecular mass of NaOH is 40. So C is Sodium Aluminate.

Al2O3 +2NaOH →2NaAlO2+H2O

55. Give the reaction involved during the extraction of zinc from its ore by (a) roasting of zinc ore (b) calcination of zinc ore

Soln:

1. 2ZnS + 3O2→2ZnO + 2SO2.
2. ZnCo3→ZnO+CO

56. A metal M does not liberate hydrogen from acids but reacts with oxygen to give a black colour product. Identify M and black coloured product and also explain the reaction of M with oxygen.

Soln:

Copper is the metal which does not react with acids. With oxygen, it forms Copper Oxide.

Metal M is Copper and black coloured product is copper oxide.

2Cu+ O2 →2CuO

57. An element forms an oxide A2O3 which is acidic in nature. Identify A as metal or non-metal.

Soln:

A is a non-metal because oxides of non-metals are acidic in nature.

58. A solution of CuSO4 was kept in an iron pot. After a few days, the iron pot was found to have a number of holes in it. Explain the reason in terms of reactivity. Write the equation of the reaction involved.

Soln:

Iron is more reactive than copper hence Iron displaces Copper to produce FeSO4. In this process, a portion of Iron Gets dissolved which results in Holes in the pot.

Fe+ CuSO4 →FeSO4+ Cu

Long Answer Questions

59. A non-metal A which is the largest constituent of air, when heated with H2 in 1:3 ratio in the presence of a catalyst (Fe) gives a gas B. On heating with O2 it gives an oxide C. If this oxide is passed into water in the presence of air, it gives an acid D which acts as a strong oxidising agent.

(a) Identify A, B, C and D

(b) To which group of periodic table does this non-metal belong?

Soln:

a)Non-metal “A” is nitrogen because it is the largest constituent of air which constitute around 78% of the gases. B is Ammonia, C is Nitrogen-di-oxide and D is Nitric acid.

When heated with H2 in 1:3 ratio in the presence of a catalyst (Fe) following reaction takes place.

3N2+3H2 →2NH3

On heating Nitrogen with O2, it gives nitrogen-di-oxide

N2 +3O →2NO2

When nitrogen-dioxide is passed into the water in the presence of air, it gives Nitric acid

NO2 + H2O →HNO3

b)Nitrogen belongs to group 15

60. Give the steps involved in the extraction of metals of low and medium reactivity from their respective sulphide ores.

Soln:

During the extraction of metals of low and medium reactivity from their respective sulphide ores.

They are first heated in the presence of atmospheric oxygen. This step will give out oxides of metal. This step is used as it is a more efficient method to extract methods.

Ex: Cinnabar is heated in air to get mercuric sulphide to oxidize to produce mercuric oxide.

2HgS+3O2 →2HgO+2SO2

Mercuric oxide is further heat to get Mercury

2HgO→ 2Hg+O2

Zinc is a metal of medium reactivity, and its ore is Zinc Blend. Zinc Blend is roasted to get Zinc oxide

2ZnS+3O2 →2ZnO+2SO2

ZNCO3 →ZnO+ CO2

Zinc oxide when heated wit CO2 Zinc is obtained

ZnO+C→ Zn+CO

61. Explain the following

(a) Reactivity of Al decreases if it is dipped in HNO3

(b) Carbon cannot reduce the oxides of Na or Mg

(c) NaCl is not a conductor of electricity in the solid-state whereas it does conduct electricity in aqueous solution as well as in molten state

(d) Iron articles are galvanised.

(e) Metals like Na, K, Ca and Mg are never found in their free state in nature.

Soln:

a) Reactivity of Aluminium decreases if it is dipped in HNO3 because HNO3 is a strong oxidizing agent. Here, a layer of aluminium oxide gets deposited because of which reactivity of aluminium gets reduced.

(b) Carbon cannot reduce the oxides of Na or Mg because these are highly reactive metals. Na and Mg have a higher affinity to oxygen than carbon. Hence carbon fails to reduce the oxides of Na and Mg.

(c) NaCl is not a conductor of electricity in the solid-state whereas it does conduct electricity in aqueous solution as well as in molten state because NaCl is an ionic compound. Ionic compounds cannot conduct electricity in the solid-state, but they can conduct electricity in aqueous solution and in a molten state.

d) Iron readily reacts with atmospheric oxygen and forms rust. To avoid rusting of iron, it is galvanized.

e) Metals like Na, K, Ca and Mg are highly reactive metals. They can form compounds with almost every element. Because of this, they are not found in their native form in nature.

62. (i) Given below are the steps for extraction of copper from its ore. Write the reaction involved.

(a) Roasting of copper (1) sulphide

(b) Reduction of copper (1) oxide with copper (1) sulphide.

(c) Electrolytic refining

(ii) Draw a neat and well-labelled diagram for electrolytic refining of copper

Soln:

1. 2Cu2S+3O2 →2Cu2O+SO2
2. 2Cu2O+ Cu2S →6Cu+ SO2
3. Cu+2  + 2e–→ Cu