CBSE Class 12 Chemistry Principles And Processes Of Isolation Of Elements Worksheet

Question. Calcination is used in metallurgy for removal of
(a) moisture
(b) water and CO₂
(c) CO₂ and H₂S
(d) H₂O and H₂S
Answer : B

Question. Which of the following pairs of metals is purified by van Arkel method ?
(a) Ga and In
(b) Zr and Ti
(c) Ag and Au
(d) Ni and Fe
Answer : B

Question. Calcination is the process in which
(a) ore is heated above its melting point to expel H₂O or CO₂ or SO₂
(b) ore is heated below its melting point to expel volatile impurities
(c) ore is heated above its melting point to remove S, As and Sb as SO₂ ,As₂O₃ and Sb₂O₃ respectively
(d) ore is heated below its melting point to expel H₂O or CO₂
Answer : D

Question. The reduction of metal oxides is sometimes done by aluminium in the
(a) Bayer reaction
(b) Zilch reaction
(c) Goldschmidt reaction
(d) Silberschmidt reaction
Answer : C

Question. In froth flotation process many chemicals (frother , collector, activator, and depressant) are used. Which of the following is a frother:
(a) CuSO₄
(b) NaCN + alkali
(c) Pine oil
(d) Potassium xanthate.
Answer : C

Question. Thomas slag is
(a) calcium silicate
(b) calcium phosphate
(c) tricalcium phosphate and calcium silicate
(d) calcium ammonium phosphate
Answer : C

Question. Which of the following is chalcopyrite?
(a) CuFeS₂
(b) FeS₂
(c) KMgCl₃.6H₂O
(d) Al₂O₃.2H₂O
Answer : A

Question. Cassiterite is concentrated by
(a) levigation
(b) electromagnetic separation
(c) floatation
(d) liquefaction
Answer : B

Question. A sulphide ore is generally roasted to the oxide before reduction, because
(a) the enthalpy of formation of CO₂ is more than that of CS₂
(b) a metal sulphide is generally more stable than the metal oxide
(c) no reducing agent is found suitable for reducing a sulphide ore
(d) a sulphide ore cannot be reduced at all
Answer : A

Question. Hydro-metallurgical process of extraction of metals is based on
(a) complex formation
(b) hydrolysis
(c) dehydration
(d) dehydrogenation
Answer : A

Question. The process of converting hydrated alumina into anhydrous alumina is called
(a) roasting
(b) smelting
(c) dressing
(d) calcination
Answer : D

Question. One of the ores of lead is known as lead pyromorphite. What is approximate composition?
(a) Pb₃O₄.PbC)₂
(b) PbSO₄.Pb(OH)₂
(c) 3Pb₃(PO4)₂.PbCl₂
(d) PbCO₃.Pb(OH)₂
Answer : C

Question. Which of the following process is generally used for the extraction of tin and lead from their chief ores ?
(a) carbon reduction and self-reduction
(b) self reduction and carbon-reduction
(c) electrolysis and self-reduction
(d) self-reduction and electrolysis
Answer : A

Question. The method of zone refining of metals is based on the principle of
(a) greater solubility of the impurities in the molten state than in the solid
(b) greater mobility of the pure metal than that of the impurite
(c) higher melting point of the impurities than that of the pure metal
(d) greater noble character of the solid metal than that of the impurities
Answer : A

Question. Nickel is purified by thermal decomposition of its
(a) hydride
(b) chloride
(c) azide
(d) carbonyl
Answer : D

Question. Composition of azurite mineral is
(a) CuCO₃CuO
(b) Cu(HCO₃)₂. Cu(OH)₂
(c) 2CuCO₃.Cu(OH)₂
(d) CuCO₃. 2Cu(OH)₂
Answer : C

Question. In order to refine “blister copper” it is melted in a furnace and is stirred with green logs of wood. The purpose is
(a) to expel the dissolved gases in blister copper.
(b) to bring the impurities to surface and oxidize them.
(c) to increase the carbon content of copper.
(d) to reduce the metallic oxide impurities with hydrocarbon gases liberated from the wood.
Answer : D

Question. Consider the following statements –
(A) In the Aluminothermite process, aluminium acts as reducing agent.
(B) The process of extraction of gold involves the formation of [Au(CN)₂]^– and [Zn(CN)₄]^2–.
(C) In the extractive metallurgy of zinc, partial fusion of ZnO with coke is called sintering and reduction of ore to the molten metal is called smelting.
(D) Extractive metallurgy of silver from its ore argentine involves complex formation and displacement by more electropositive metal.
Choose the correct options –
(a) A and B
(b) B and C
(c) A, B and C
(d) A, B, C and D
Answer : D

Question. Carbon cannot be used in the reduction of Al₂O₃  because
(a) the enthalpy of formation of CO₂ is more than that of Al₂O₃
(b) pure carbon is not easily available
(c) the enthalpy of formation of Al₂O₃ is very high
(d) it is an expensive proposition
Answer : C

Question. Muffle furnace is used in the metallurgy of
(a) Zn
(b) Sn
(c) Pb
(d) Cu
Answer : A

1. Name chief ore of Iron and Aluminium.

2. At what temperature CO is better reducing agent than carbon?

3. What is meant by gangue?

4. Name the impurities associated with bauxite.

5. What is the basis of zone refining?

6. What is the basis of vapour phase refining?

7. Name the refining method used for high degree of purity of metal.

8. How is copper extracted from low grade copper ore?

9. What is the role of collectors in froth floatation process?

10. Name two metals that occur in nature as oxides.

11. Out of C and CO which is better reducing agent for ZnO?

12. What is the role of cryolite in electrometallurgy of aluminum?

13. Why is Bauxite not heated to remove the impurities of water associated with it?

14. Copper can be extracted by hydrometallurgy but not Zn. Why?

15. What is the role of CaF₂ in electrometallurgy of aluminum?

16. Why is CaCO₃ added to blast furnace during reduction of Haematite?

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