Chemistry NCERT Exemplar Solutions Class 12th Chapter Six

34. Which of the following options are correct?

(i) Cast iron is obtained by smelting pig iron with scrap iron and coke using hot air blast.

(ii) In extraction of silver, silver is extracted as a cationic complex.

(iii) Nickel is purified by zone refining.

(iv) Zr and Ti are purified by van Arkel method.

Note: In the following questions two or more options may be correct.

33. At the temperature corresponding to which of the points in Fig.6.1, FeO will be reduced to Fe by coupling the reaction 2FeO→2Fe+O₂with all of the following reactions?

(a) C+O₂ → CO₂ 

(b) 2C+O₂ → 2CO and

(c) 2CO + O₂ → 2CO₂.

(i) Point A

(ii) Point B

(iii) Point D

(iv) Point E

32. For the reduction of FeO at the temperature corresponding to point D, which of the following statements is correct?

(i) ΔG value for the overall reduction reaction with carbon monoxide is zero.

(ii) ΔG value for the overall reduction reaction with a mixture of 1 mol carbon and 1 mol oxygen is positive.

(iii) ΔG value for the overall reduction reaction with a mixture of 2 mol carbon and 1 mol oxygen will be positive.

(iv) ΔG value for the overall reduction reaction with carbon monoxide is negative.

31. Below point ' A ' FeO can

(i) Be reduced by carbon monoxide only. 

(ii) Be reduced by both carbon monoxide and carbon.

(iii) Be reduced by carbon only.

(iv) Not be reduced by both carbon and carbon monoxide.

Note : Answer the questions 11-13 on the basis of Fig. 6.1.

30. Choose the correct option of temperature at which carbon reduces FeO to iron and produces CO

(i) Below temperature at point A.

(ii) Approximately at the temperature corresponding to point A.

(iii) Above temperature at point A but below the temperature at point D.

(iv) Above temperature at point A.

29. Extraction of gold and silver involves leaching the metal with CN⁻ion. The metal is recovered by

(i) Displacement of metal by some other metal from the complex ion.

(ii) Roasting of metal complexes.

(iii) Calcination followed by roasting.

(iv) Thermal decomposition of metal complexes.

28. Electrolytic refining is used to purify which of the following metals?

(i) Cu and Zn

(ii) Ge and Si

(iii) Zr and Ti

(iv) Zn and Hg

27. In the metallurgy of aluminum

(i) Al³⁺ is oxidized to Al (s).

(ii) Graphite anode is oxidized to carbon monoxide and carbon dioxide.

(iii) Oxidation state of oxygen changes in the reaction at anode.

(iv) Oxidation state of oxygen changes in the overall reaction involved in the process.

26. Brine is electrolysed by using inert electrodes. The reaction at anode is 

(i) Cl⁻(aq)→ $\mathbf{}\frac{1}{2}$ Cl₂(g)+ e−;E $°$ _cell =1.36 V

(ii) 2H₂O(l)→O₂(g) + 4H⁺ + 4e⁻, E $°$ _cell  = 1.23 V

(iii) Na+(aq.)+ e→Na(s); E $°$ _cell = 2.71 V

(iv) H⁺(aq) + e⁻→12H₂(g); E $°$ _cell  = 0.00 V

25. In the extraction of copper from its sulfide ore, the metal is formed by the reduction of Cu₂O with

(i) FeS

(ii) CO

(iii) Cu₂S

(iv) SO₂