How many of the following statements related to metal extraction processes are correct? (i) A mixture of PbS and PbO undergoes self-reduction to produce Pb and SO2. (ii) Liquation method is used to refine metals that have high melting points and are associated with low-melting-point impuri

Question

How many of the following statements related to metal extraction processes are correct? (i) A mixture of PbS and PbO undergoes self-reduction to produce Pb and SO2. (ii) Liquation method is used to refine metals that have high melting points and are associated with low-melting-point impurities. (iii) Partial roasting of copper sulphide ore followed by self-reduction yields blister copper. (iv) In the cyanide process, zinc powder is used to precipitate gold from Na[Au(CN)2]. (v) Blister copper is refined by carbon reduction.

Accepted Answer

3. (i) Correct: PbS + 2PbO -> 3Pb + SO2 (self-reduction). (ii) Incorrect: Liquation is used for metals with LOW melting points (like Sn, Bi) mixed with high-melting impurities, not the reverse. (iii) Correct: 2Cu2S + 3O2 -> 2Cu2O + 2SO2 (roasting); Cu2S + 2Cu2O -> 6Cu + SO2 (self-reduction -> blister copper). (iv) Correct: 2Na[Au(CN)2] + Zn -> Na2[Zn(CN)4] + 2Au (precipitation by zinc). (v) Incorrect: Blister copper is refined by electrolytic refining (electrolysis), not carbon reduction. Correct statements: (i), (iii), (iv) = 3.

Solution

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