NCERT Exemplar for Class 10 Science Chapter 3 - Metals and Non-metals (Book Solutions)

Multiple Choice Questions

1. Which of the following property is generally not shown by metals (except some metals)?

(a) Electrical conduction

(b) Sonorous in nature

(c) Dullness

(d) Ductility

Ans: Correct option is (c) – Dullness

2. The ability of metals to be drawn into the thin wire is known as

(a) Ductility

(b) Malleability

(c) Sonorousity

(d) Conductivity

Ans: Correct option is (a) - Ductility

3. Aluminium is used for making cooking utensils. Which of the aluminium are responsible for the same?

(i) Good thermal conductivity or good heat conduction

(ii) Good conduction of electricity

(iii) Ductility

(iv) High melting point

(a) (i) and (ii)

(b) (i) and (iii)

(c) (ii) and (iii)

(d) (i) and (iv)

Ans: Correct option is (d) - (i) and (iv)

Because as we know Electrical conductivity and ductility have no relevance for a cooking utensil and it does not enhance cooking.

4. Which one of the following metals do not react with cold as well as hot water?

(a) Sodium ${\text{Na}}$

(b) Calcium ${\text{Ca}}$

(c) Magnesium ${\text{Mg}}$

(d) Iron ${\text{Fe}}$

Ans: Correct option is (d) - Iron ${\text{Fe}}$

Because as we know Sodium and calcium react vigorously with water whereas magnesium reacts with hot water to form magnesium oxide and Iron reacts with steam.

5. Which of the following oxide(s) of iron would be obtained on prolonged reaction of iron with steam?

(a) ${\text{FeO}}$

(b) ${\text{F}}{{\text{e}}_{\text{2}}}{{\text{O}}_{\text{3}}}$

(c) ${\text{F}}{{\text{e}}_3}{{\text{O}}_4}$

(d)${\text{F}}{{\text{e}}_{\text{2}}}{{\text{O}}_{\text{3}}}{\text{, F}}{{\text{e}}_{\text{3}}}{{\text{O}}_{\text{4}}}$

Ans: Correct option is (c) because this equation shows reaction between iron and stream. Equation is $3{\text{Fe}} + 4{{\text{H}}_2}{\text{O}} \to {\text{F}}{{\text{e}}_3}{{\text{O}}_4} + 4{{\text{H}}_2}$

6. What happens when calcium is treated with water?

(i) It does not react with water

(ii) It reacts violently with water

(iii) It reacts less violently with water

(iv) Bubbles of hydrogen gas formed stick to the surface of calcium

(a) (i) and (iv)

(b) (ii) and (iii)

(c) (i) and (ii)

(d) (iii) and (iv)

Ans: Correct option is (d) because Calcium reacts less violently with water and it starts floating as it sticks to hydrogen bubbles.

${\text{Ca}} + 2{{\text{H}}_2}{\text{O}} \to {\text{Ca}}{({\text{OH}})_2} + {{\text{H}}_2}$

7. Generally metals react with acids to give salt and hydrogen gas. Which of the following acids does not give hydrogen gas on reacting with metals (except ${\text{Mn}}~and~{\text{Mg}})$?

(a) ${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$

(b) ${\text{HCl}}$

(c) ${\text{HN}}{{\text{O}}_{\text{3}}}$

(d) All of these

Ans: Correct option is (c) ${\text{HN}}{{\text{O}}_{\text{3}}}$ because Nitric acid is a potent oxidizing agent and reacts with hydrogen to form water.

8. The composition of aqua-regia is

(a) Dil. HCl: Conc. ${\text{HN}}{{\text{O}}_{\text{3}}}{\text{(3:1)}}$

(b) Conc. HCl: Dil. ${\text{HN}}{{\text{O}}_{\text{3}}}{\text{(3:1)}}$

(c) Conc. HCl: Conc. ${\text{HN}}{{\text{O}}_{\text{3}}}{\text{(3:1)}}$

(d) Dil. HCl: Dil. ${\text{HN}}{{\text{O}}_{\text{3}}}{\text{(3:1)}}$

Ans: Correct option is (b) Conc. HCl: Dil. ${\text{HN}}{{\text{O}}_{\text{3}}}{\text{(3:1)}}$

9. Which of the following are not ionic compounds?

(i) ${\text{KCl}}$

(ii) ${\text{HCl}}$

(iii) ${\text{CC}}{{\text{l}}_4}$ 

(iv) ${\text{NaCl}}$ 

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (iii) and (iv)

(d) (i) and (iii)

Ans: Correct option is (b) (ii) and (iii) because These are covalent compounds and Both are constituents in each compound are non-metals.

10. Which one of the following properties is not generally exhibited by ionic compounds?

(a) Solubility in water

(b) Electrical conductivity in solid-state

(c) High melting and boiling points

(d) Electrical conductivity in a molten state

Ans: Correct option is (b) Electrical conductivity in solid-state

Because in this Free ions are required for electrical conductivity and in ionic compounds, free ions are not available in solid-state.

11. Which of the following metals exist in their native state in nature?

(i) ${\text{Cu}}$

(ii) ${\text{Au}}$

(iii) ${\text{Zn}}$

(iv) ${\text{Ag}}$

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (ii) and (iv)

(d) (iii) and (iv)

Ans: Correct option is (c) (ii) and (iv) because Gold and silver are noble metals and least reactive metals. Thus, they are found in their native state in nature.

12. Metals are refined by using different methods. Which of the following metals are refined by electrolytic refining?

(i) ${\text{Au}}$

(ii) ${\text{Cu}}$

(iii) ${\text{Na}}$

(iv) ${\text{K}}$

(a) (i) and (ii)

(b) (i) and (iii)

(c) (ii) and (iii)

(d) (iii) and (iv)

Ans: Correct option is (d) (iii) and (iv) because these metals are at the top of reactivity series so refined by electrolytic refining.

13. Silver articles become black on prolonged exposure to air. This is due to the formation of

(a) ${\text{A}}{{\text{g}}_{\text{3}}}{\text{N}}$

(b) ${\text{A}}{{\text{g}}_{\text{2}}}{\text{O}}$

(c) ${\text{A}}{{\text{g}}_{\text{2}}}{\text{S}}$

(d) ${\text{A}}{{\text{g}}_{\text{2}}}{\text{S , A}}{{\text{g}}_{\text{3}}}{\text{N}}$

Ans: Correct option is (c)

14. Galvanisation is a method of protecting iron from rusting by coating with a thin layer of

(a) Gallium

(b) Aluminium

(c) Zinc

(d) Silver

Ans: (c) Zinc because as we know that applying a layer of zinc through electrolysis is known as galvanization.

15. Stainless steel is very useful material for our life. In stainless steel, iron is mixed with

(a) ${\text{Ni , Cr}}$

(b) ${\text{Cu , Cr}}$

(c) ${\text{Ni , Cu}}$

(d) ${\text{Cu , Au}}$

Ans: Correct option is (a) ${\text{Ni , Cr}}$

16. If copper is kept open in air, it slowly loses its shining brown surface and gains a green coating. It is due to the formation of

(a) ${\text{CuS}}{{\text{O}}_4}$

(b) ${\text{CuC}}{{\text{O}}_{\text{3}}}$

(c) ${\text{Cu(N}}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}}$

(d) ${\text{CuO}}$

Ans: Correct option is (d) ${\text{CuO}}$ because when copper is kept in the open air it reacts with oxygen to form a copper oxide which appears as a greenish layer.

17. Generally, metals are solid in nature. Which one of the following metals is found in a liquid state at room temperature?

(a) ${\text{Na}}$

(b) ${\text{Fe}}$

(c) ${\text{Cr}}$

(d) ${\text{Hg}}$

Ans: Correct option is (d) ${\text{Hg}}$ because mercury is the metal that presents in the liquid state at room temperature.

18. Which of the following metals are obtained by electrolysis of their chlorides in a molten state?

(i) ${\text{Na}}$

(ii) ${\text{Ca}}$

(iii) ${\text{Fe}}$

(iv) ${\text{Cu}}$

(a) (i) and (iv)

(b) (iii) and (iv)

(c) (i) and (iii)

(d) (i) and (ii)

Ans: Correct option is (d) (i) and (ii) because these metals are at the top of the reactivity series.

19. Generally, non-metals are not lustrous. Which of the following non-metal is lustrous?

(a) Sulphur

(b) Oxygen

(c) Nitrogen

(d) Iodine

Ans: Correct option is (d) Iodine

20. Which one of the following four metals would be displaced from the solution of its salts by other three metals?

(a) ${\text{Mg}}$

(b) ${\text{Ag}}$

(c) ${\text{Zn}}$

(d) ${\text{Cu}}$

Ans: Correct option is (b) Because as we know that silver is the least reactive metal among the given metals.

21. ${\text{2 mL}}$ each of concentrated ${\text{HCl$, $HN}}{{\text{O}}_3}$ and a mixture of concentrated ${\text{HCl}}$ and concentrated ${\text{HN}}{{\text{O}}_3}$ in the ratio of $3:1$ were taken in test tubes labelled as A, B, C. A small piece of metal was put in each test tube. No change occurred in test tubes A and B but the metal got dissolved in test tube C respectively. The metal could be

(a) ${\text{Al}}$

(b) ${\text{Au}}$

(c) ${\text{Cu}}$

(d) ${\text{Pt}}$

Ans: Correct option is (b) because the mixture in test tube C is known as Aqua Regia and it dissolves gold.

22. An alloy is

(a) an element

(b) a compound

(c) a homogeneous mixture

(d) a heterogeneous mixture

Ans: Correct option is (c) Because components of alloy retain their chemical properties. Thus, alloy cannot be a compound and its composition is uniform so it is a homogeneous mixture.

23. An electrolytic cell consists of

(i) positively charged cathode

(ii) negatively charged anode

(iii) positively charged anode

(iv) negatively charged cathode

(a) (i) and (ii)

(b) (iii) and (iv)

(c) (i) and (iii)

(d) (ii) ad (iv)

Ans: Correct option is (b) because negatively charged particles (anions) move towards anode and shows that anode is positively charged.

24. During electrolytic refining of zinc, it gets

(a) deposited on cathode

(b) deposited on anode

(c) deposited on the cathode as well as anode

(d) remains in the solution

Ans: Correct option is (a) because Zinc is positively charged and deposited at a negatively charged cathode.

25. An element A is soft and can be cut with a knife. This is very reactive to air and cannot be kept open in the air. It reacts vigorously with water. Identify the element from the following

(a) ${\text{Mg}}$

(b) ${\text{Na}}$

(c) ${\text{P}}$

(d) ${\text{Ca}}$

Ans: Correct option is (b) because as we know Sodium is soft and it can be cut with a knife so reacts vigorously with water and air and is kept in kerosene to prevent a reaction.

26. Alloys are homogeneous mixtures of a metal with a metal or non-metal. Which among the following alloys contain non-metal as one of its constituents?

(a) Brass

(b) Bronze

(c) Amalgam

(d) Steel

Ans: Correct option is (d) because Steel contains carbon along with iron.

27. Which among the following statements is incorrect for magnesium metal?

(a) It burns in oxygen with a dazzling white flame

(b) It reacts with cold water to form magnesium oxide and evolves hydrogen gas

(c) It reacts with hot water to form magnesium hydroxide and evolves hydrogen gas

(d) It reacts with steam to form magnesium hydroxide and evolves hydrogen gas

Ans: Correct option is (a) because Magnesium does not react with cold water and reacts with hot water to form magnesium oxide. Thus, other options are incorrect.

28. Which among the following alloys contain mercury as one of its constituents?

(a) Stainless steel

(b) Alnico

(c) Solder

(d) Zinc amalgam

Ans: Correct option is (d) because Alloys of mercury are called amalgam.

29. Reaction between X and Y forms compound Z. X loses electron and Y gains electron. Which of the following properties is not shown by Z?

(a) Has high melting point

(b) Has low melting point

(c) Conducts electricity in molten state

(d) Occurs as solid

Ans: Correct option is (b) because  Z is an ionic compound and Ionic compound have high melting point so they occur as solid. Hence, conduct electricity in molten state.

30. The electronic configurations of three elements X, Y, Z are X- $(2,8); Y- (2,8,7); Z- (2,8,2)$  Which of the following is correct?

(a) X is a metal

(b) Y is a metal

(c) Z is a non-metal

(d) Y is a non-metal and Z is a metal

Ans: Correct option is (d) because Y has seven electrons in its outermost shell which implies Y is an electronegative element and thus is a non-metal. Z has two electrons in its outermost shell. This means Z is an electropositive element and thus is a metal.

31. Although metals form basic oxides, which of the following metals form an amphoteric oxide?

(a) ${\text{Na}}$

(b) ${\text{Ca}}$

(C) ${\text{Al}}$

(d) ${\text{Cu}}$

Ans: Correct option is (c) because the Oxide of the aluminium shows both acidic and basic behaviour so it is an amphoteric oxide.

32. Generally, non-metals are not conductors of electricity. Which of the following is a good conductor of electricity?

(a) Diamond

(b) Graphite

(c) Sulphur

(d) Fluorine

Ans: Correct option is (b) 

33. Electrical wires have a coating of insulating material. The material, generally used is

(a) Sulphur

(b) Graphite

(c) PVC

(d) All can be used

Ans: Correct option is (c) because Sulphur is highly brittle so cannot be used whereas Graphite is a good conductor of electricity so it cannot be used for insulation.

34. Which of the following non-metals is a liquid?

(a) Carbon

(b) Bromine

(c) Phosphorus

(d) Sulphur

Ans: Correct option is (b) 

35. Which of the following can undergo a chemical reaction?

(a) ${\text{MgS}}{{\text{O}}_{\text{4}}}{\text{ + Fe}}$

(b) ${\text{ZnS}}{{\text{O}}_{\text{4}}}{\text{ + Fe}}$

(c) ${\text{MgS}}{{\text{O}}_{\text{4}}}{\text{ + Pb}}$

(d) ${\text{CuS}}{{\text{O}}_{\text{4}}}{\text{ + Fe}}$

Ans: Correct option is (d) because Iron is more reactive than copper. Thus, iron displaces copper from copper sulphate solution.

36. Which one of the following figures correctly describes the process of electrolytic refining?

Ans: Correct option is (b) because copper ions are liberated from the positively charged anode and getting deposited on the negatively charged cathode.

Short Answer Questions

37. Iqbal treated lustrous, divalent element M with sodium hydroxide. He observed the formation of bubbles in the 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 reactions.

Ans: Here Burning matchstick should be brought near the evolved gas. If matchstick burns with a pop sound then it indicates the evolution of hydrogen gas.

So, Reaction with ${\text{NaOH}}$ are as follows:

\[{\text{M + 2NaOH}} \to {\text{N}}{{\text{a}}_{\text{2}}}{\text{M}}{{\text{O}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}\]

Reaction with ${\text{HCl}}$ are as follows:

${\text{M + 2HCl}} \to {\text{MC}}{{\text{l}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}$

38. During 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?

Ans: During electrolytic refining, impure metal is used as anode whereas pure metal is used as cathode. Thus, impure silver will be used as anode whereas pure silver will be used as cathode.

(b) Suggest a suitable electrolyte also.

Ans: Silver sulphate or Silver nitrate solution can be a suitable electrolyte.

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

Ans: Pure silver will be obtained on the cathode as we know metals are electropositive.

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

Ans: Here, It is easier to obtain metal from its oxide than from its sulphides or carbonates. Thus, the process of extraction of metal from metal sulphides and carbonates shows they are first converted to metal oxides.

40. Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except ${\text{Mn, Mg}}$ ), treated with ${\text{HN}}{{\text{O}}_3}$, hydrogen is not liberated, why?

Ans: So here as Hydrogen gas is not evolved when a metal reacts with nitric acid  because ${\text{HN}}{{\text{O}}_3}$ is a strong oxidising agent which oxidises the ${{\text{H}}_{\text{2}}}$ produced to water and itself gets reduced to any of the nitrogen oxides $\left( {{{\text{N}}_{\text{2}}}{\text{O, NO, N}}{{\text{O}}_{\text{2}}}} \right){\text{.s}}$

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

(a) Identify the compound X 

Ans: Compound X is iron oxide $\left( {{\text{F}}{{\text{e}}_{\text{2}}}{{\text{O}}_{\text{3}}}} \right)$ 

(b)  Name the reaction 

Ans: This reaction is called thermite reaction. 

(c) Write down its reaction.

Ans: Reaction is ${\text{2Al + F}}{{\text{e}}_{\text{2}}}{{\text{O}}_{\text{3}}} \to {\text{2Fe + A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}{\text{ + heat}}$

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

Ans: X is sodium because molar mass of ${\text{NaOH  =  40}}$ which can be shown as follows:

${\text{Na(23) + O(16) + H(1)  =  40}}$

Hence, Y is ${\text{NaOH}}$

Z is hydrogen which easily catches fire and reaction between sodium and water is as follows: ${\text{2Na + 2}}{{\text{H}}_{\text{2}}}{\text{O}} \to {\text{2NaOH + }}{{\text{H}}_{\text{2}}}$

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.

Ans: X is carbon and we know Diamond and graphite are allotropes of carbon. As Diamond is the hardest natural substance and Thus Y is diamond. Graphite is a good conductor of electricity and hence Z is graphite.

44. The following reaction takes place when aluminium powder is heated with ${\text{Mn}}{{\text{O}}_{\text{2}}}$

${\text{3Mn}}{{\text{O}}_{\text{2}}}{\text{(s) + 4}}{\text{.Al(s)}} \to {\text{3Mn(l) + 2A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}{\text{(l) +  Heat }}$

(a) Is aluminium getting reduced?

Ans: In this reaction, aluminium is getting oxidized because oxygen gets combined to it.

(b) Is ${\text{Mn}}{{\text{O}}_{\text{2}}}$  getting oxidised?

Ans: Since oxygen is removed from manganese dioxide hence ${\text{Mn}}{{\text{O}}_{\text{2}}}$  is getting reduced.

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

Ans: Lead and tin are the constituents of the solder alloy. Solder alloy has a low melting point which is suitable for welding electrical wires.

46. A metal A, which is used in the 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 ${\text{HCl, NaOH}}$

Ans: Metal A is aluminium and B is ${\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}$

Reaction of aluminium oxide with ${\text{HCl}}$ as follows:

${\text{A}}{{\text{l}}_2}{{\text{O}}_3} + 6{\text{HCl}} \to 2{\text{AlC}}{{\text{l}}_3} + 3{{\text{H}}_2}{\text{O}}$

Reaction of aluminium oxide with ${\text{NaOH}}$ as follows:

${\text{A}}{{\text{l}}_2}{{\text{O}}_3} + 2{\text{NaOH}} \to 2{\text{NaAl}}{{\text{O}}_2} + {{\text{H}}_2}{\text{O}}$

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.

Ans: This metal is mercury because mercury exists as liquid at room temperature and Mercury ore is called cinnabar ${\text{HgS}}$ . When cinnabar is heated in presence of air then it follows the reaction $2{\text{HgS}} + 3{{\text{O}}_2} \to 2{\text{HgO}} + 2{\text{S}}{{\text{O}}_2}$

Now, Mercury oxide is further heated to obtain mercury $2{\text{HgO}} \to 2{\text{Hg}} + {{\text{O}}_2}$

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

(a) ${\text{Mg , }}{{\text{N}}_2}$

Ans: Magnesium nitride ${\text{M}}{{\text{g}}_{\text{3}}}{{\text{N}}_{\text{2}}}$

(b) ${\text{Li , }}{{\text{O}}_2}$

Ans: Lithium oxide ${\text{L}}{{\text{i}}_{\text{2}}}{\text{O}}$

(c) ${\text{Al , C}}{{\text{l}}_2}$

Ans: Aluminum chloride ${\text{AlC}}{{\text{l}}_{\text{3}}}$

(d) ${\text{K , }}{{\text{O}}_2}$

Ans: Potassium oxide ${{\text{K}}_{\text{2}}}{\text{O}}$

49. What happens when

(a) ${\text{ZnC}}{{\text{O}}_3}$ is heated in the absence of oxygen?

Ans: When zinc carbonate is heated in the absence of oxygen then we get zinc oxide and carbon dioxide which shows in reaction as follows:

${\text{ZnC}}{{\text{O}}_3} \to {\text{ZnO}} + {\text{C}}{{\text{O}}_2}$

(b) a mixture of ${\text{C}}{{\text{u}}_2}{\text{O , C}}{{\text{u}}_2}\;{\text{S}}$ is heated?

Ans: When a mixture of copper oxide and copper sulphide is heated, we get pure copper shown in following reaction:

$2{\text{C}}{{\text{u}}_2}{\text{O}} + {\text{C}}{{\text{u}}_2}\;{\text{S}} \to 6{\text{Cu}} + {\text{S}}{{\text{O}}_2}$

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

Ans: Here A is carbon, B is carbon monoxide whereas C is carbon dioxide.

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

Ans: In periodic table Carbon belongs to group $14$

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

Ans: Examples of good conductors of heat and electricity are Iron and copper whereas examples of poor conductors of heat and electricity are Lead and mercury

52. Name one metal and one non-metal that exist in liquid state at room temperature. Also, name two metals having melting point less than 310K \[(37^{\circ})\].

Ans: Here Mercury is metal and bromine is non-metal which exists in liquid state at room temperature whereas Caesium and gallium are metals with melting point less than ${\text{310 K}}$

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, C and give the reactions involved.

Ans: A is calcium which reacts with water to give calcium hydroxide whereas B is calcium hydroxide which is used for white washing and C is calcium oxide. So, reactions are as follows:

${\text{Ca + 2}}{{\text{H}}_{\text{2}}}{\text{O}} \to {\text{Ca(OH}}{{\text{)}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}$

  ${\text{Ca(OH}}{{\text{)}}_{\text{2}}} \to {\text{CaO + }}{{\text{H}}_{\text{2}}}{\text{O}}$                                                                                                                                                                                                                                                                                                                                 

  ${\text{CaO + }}{{\text{H}}_{\text{2}}}{\text{O}} \to {\text{Ca(OH}}{{\text{)}}_{\text{2}}}$

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

Ans: Here, A is sodium as molar mass of ${\text{NaOH  =  40}}$ which can be shown as follows: 

${\text{Na}}(23) + {\text{O}}(16) + {\text{H}}({\text{l}}) = 40$

And B is ${\text{NaOH}}$ when sodium hydroxide is treated with aluminium oxide then we get sodium aluminate. Thus, C is sodium aluminate. Hence the reaction is as follows:

${\text{A}}{{\text{l}}_2}{{\text{O}}_3} + 2{\text{NaOH}} \to 2{\text{NaAl}}{{\text{O}}_2} + {{\text{H}}_2}{\text{O}}$

55. Give the reaction involved during extraction of zinc from its ore by

(a) roasting of zinc ore

Ans: $2{\text{ZnS}} + 3{{\text{O}}_2} \to 2{\text{ZnO}} + 2{\text{S}}{{\text{O}}_2}$

(b) calcination of zinc ore

Ans: ${\text{ZnC}}{{\text{O}}_3} \to {\text{ZnO}} + {\text{C}}{{\text{O}}_2}$

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 products and also explain the reaction of M with oxygen.

Ans: As we know Copper does not react with acids but gives black coloured copper oxide when it reacts with oxygen. Thus, M is copper and the black coloured product is copper oxide. The reaction is as follows:

$2{\text{Cu}} + {{\text{O}}_2} \to 2{\text{CuO}}$

57. An element forms an oxide ${{\text{A}}_2}{{\text{O}}_3}$ which is acidic in nature. Identify A as metal or non-metal.

Ans: As we know Oxides of non-metals are acidic in nature. Thus, A is a non-metal.

58. A solution of ${\text{CuS}}{{\text{O}}_4}$ 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.

Ans: As Iron is more reactive than copper. So, iron displaced copper from copper sulphate to form iron sulphate. Thus, portion of iron pot got dissolved in this process and caused holes in it. In this reaction, equation is as follows:

${\text{CuS}}{{\text{O}}_4} + {\text{Fe}} \to {\text{FeS}}{{\text{O}}_4} + {\text{Cu}}$

Long Answer Questions

59. A non-metal A which is the largest constituent of air, when heated with ${{\text{H}}_2}\] in \[1:3$ ratio in the presence of catalyst  ${\text{Fe}}$ gives a gas B. On heating with ${{\text{O}}_2}$ it gives an oxide C. If this oxide is passed into the 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

Ans: Here, A is nitrogen as nitrogen is the largest constituent of air whereas B is ammonia, C is nitrogen dioxide and D is nitric acid as nitric acid is a strong oxidizing agent. When nitrogen is heated with hydrogen in the presence of a catalyst. In that case, the reaction is as follows:

${{\text{N}}_2} + 3{{\text{H}}_2} \to 2{\text{N}}{{\text{H}}_3}$

When nitrogen is heated with oxygen, we get nitrogen dioxide: ${{\text{N}}_2} + 2{{\text{O}}_2} \to 2{\text{N}}{{\text{O}}_2}$

When nitrogen dioxide is treated with water then we get nitric acid: ${\text{N}}{{\text{O}}_2} + {{\text{H}}_2}{\text{O}} \to {\text{HN}}{{\text{O}}_3}$

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

Ans: In the periodic table, non-metal belongs to Group $15$

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

Ans: Firstly, Sulphide ore is heated in the air during extraction of metals of low and medium reactivity which helps in obtaining oxide of metal and It is easier to extract a metal from its oxide rather than from its sulphide. Thus, this step is used. As Mercury is a metal of low reactivity. Mercury sulphide (cinnabar) is heated in the air and gets oxidized to produce mercury oxide.

$2{\text{HgS}} + 3{{\text{O}}_2} \to 2{\text{HgO}} + 2{\text{S}}{{\text{O}}_2}$

After that, mercury oxide is reduced to obtain mercury.

$2{\text{HgO}} \to 2{\text{Hg}} + {{\text{O}}_2}$

Zinc is a metal of medium reactivity and found as zinc blende ${\text{ZnS}}$ and it is roasted to be converted into zinc oxide. Zinc spar is put under calcination to be converted into zinc oxide.

$2{\text{ZnS}} + 3{{\text{O}}_2} \to 2{\text{ZnO}} + 2{\text{S}}{{\text{O}}_2}$

${\text{ZnC}}{{\text{O}}_3} \to {\text{ZnO}} + {\text{C}}{{\text{O}}_2}$

So, Zinc oxide is reduced to zinc metal by heating with carbon which is a reducing agent.

${\text{ZnO}} + {\text{C}} \to {\text{Zn}} + {\text{CO}}$

61. Explain the following

(a) Reactivity of Al decreases if it is dipped in \[HNO{_3}\].

Ans: As Nitric acid is a strong oxidizing agent because of this, when aluminium is dipped in nitric acid we get a layer of aluminium oxide deposited on aluminium. So, the reactivity of Aluminium decreases when it is dipped in nitric acid.

(b) Carbon cannot reduce the oxides of \[{\text{Na or Mg}}\]

Ans: Here ${\text{Na or Mg}}$ represents Sodium or magnesium respectively and they are highly reactive metals. Thus, both have a higher affinity to oxygen than carbon. So, carbon fails to reduce the oxides of sodium or magnesium.

(c) ${\text{NaCl}}$ is not a conductor of electricity in a solid-state whereas it does conduct electricity in an aqueous solution as well as in a molten state

Ans: As ${\text{NaCl}}$ is an ionic compound and we know Ionic compounds do not conduct electricity in the solid state because ionic compounds are good conductors of electricity in a molten state and in an aqueous solution.

(d) Iron articles are galvanised.

Ans: As Iron has a tendency to react with atmospheric moisture which is called rusting. It leads to corrosion of iron where Iron articles are galvanized to prevent rusting of iron.

(e) Metals like ${\text{Na, K, Ca, Mg}}$ are never found in their free state in nature.

Ans: As these ${\text{Na, K, Ca, Mg}}$ are highly reactive metals that easily form compounds with most of the elements. So, these metals are not found in their free state 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

Ans: $2{\text{C}}{{\text{u}}_2}\;{\text{S}} + 3{{\text{O}}_2} \to 2{\text{C}}{{\text{u}}_2}{\text{O}} + 2{\text{S}}{{\text{O}}_2}$

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

Ans: $2{\text{C}}{{\text{u}}_2}{\text{O}} + {\text{C}}{{\text{u}}_2}\;{\text{S}} \to 6{\text{Cu}} + {\text{S}}{{\text{O}}_2}$

(c) Electrolytic refining

Ans: At cathode we have ${\text{C}}{{\text{u}}^{{\text{2 + }}}}{\text{ + 2}}{{\text{e}}^{\text{ - }}} \to {\text{Cu}}$

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

Ans: 

In the above figure, It shows the electrolytic refining of copper. An electrolyte is a solution of acidified copper sulphate. So, the anode is impure copper whereas the cathode is a strip of pure copper. Thus, on passing electric current, pure copper is deposited on the cathode.

63. Of the three metals X, Y, Z reacts with cold water. Y with hot water and Z with steam only. Identify X, Y, Z and also arrange them in order of increasing reactivity.

Ans: Here X is sodium, Y is magnesium and Z is iron.

$2{\text{Na}} + 2{{\text{H}}_2}{\text{O}} \to 2{\text{NaOH}} + {{\text{H}}_2}$

${\text{Mg}} + 2{{\text{H}}_2}{\text{O}} \to {\text{Mg}}{({\text{OH}})_2} + {{\text{H}}_2}$

$3{\text{Fe}} + 4{{\text{H}}_2}{\text{O}} \to {\text{F}}{{\text{e}}_3}{{\text{O}}_4} + 4{{\text{H}}_2}$

Now, sequence in reactivity series is as follows:

${\text{Fe}} < {\text{Mg}} < {\text{Na}}$

64. An element A burns with golden flame in air. It reacts with another element B, atomic number $17$ to give a product C. An aqueous solution of product C on electrolysis gives a compound D and liberates hydrogen. Identify A, B, C and D. Also, write down the equations for the reactions involved.

Ans: Here A is sodium. B is chlorine with the atomic number $17$. C is sodium chloride and D is sodium hydroxide.

$2{\text{Na}} + {\text{C}}{{\text{l}}_2} \to 2{\text{NaCl}}$

Electrolysis of sodium chloride can be given by following equation: $2{\text{NaCl}} + 2{{\text{H}}_2}{\text{O}} \to 2{\text{NaOH}} + {\text{C}}{{\text{l}}_2} + {{\text{H}}_2}$

65. Two ores A and B were taken. On heating ore A gives $\[CO_{2}\] whereas, ore B gives \[SO{_2}\] What steps will you take to convert them into metals?

Ans: When a carbonate ore is heated then we get carbon dioxide. A carbonate ore is calcinated to obtain oxide of the metal. So, equation shows calcinations of zinc carbonate as follows:

${\text{ZnC}}{{\text{O}}_3} \to {\text{ZnO}} + {\text{C}}{{\text{O}}_2}$

When a sulphide ore is roasted, we get Sulphur dioxide and Zinc sulphide is roasted to obtain zinc oxide.

$2{\text{ZnS}} + 3{{\text{O}}_2} \to 2{\text{ZnO}} + 2{\text{S}}{{\text{O}}_2}$

After any of the above steps; zinc oxide is reduced to obtain pure zinc.

${\text{ZnO}} + {\text{C}} \to {\text{Zn}} + {\text{CO}}$

Benefits of using NCERT Exemplar for Class 10 Science Chapter 3

Students can use the NCERT Exemplar for Class 10 Science chapter 3 because it has many advantages that are listed here:

• Students can clear their doubts by solving more questions from the chapter given in the Exemplar. Students can practice more questions for the exams and can score high marks.

• The questions given in the Exemplar book are based on the concepts and ideas of the latest syllabus. Students can get an idea about the type of questions asked in the exams. 

• Exemplar book for class 10 science is an excellent book as it consists of different types of questions based on the latest pattern of the exam. 

• It includes a variety of questions based on the chapter that can help students in the thorough understanding of the concepts given in the chapter.