Exams › JEE Advanced › Chemistry
Which of the following conversions correctly represents the indicated metallurgical process? (A) PbSO4 -> PbO + SO2 + (1/2)O2 (roasting) (B) PbSO4 + PbS -> Pb + 2SO2 (self-reduction) (C) 2Na[Ag(CN)2] + Zn -> Na2[Zn(CN)4] + 2Ag (extraction from leached solution) (D) CuSO4(aq) + 2Ag -> Ag2SO4(aq) + Cu (metal displacement method)
- PbSO4 -> PbO + SO2 + (1/2)O2 (roasting)
- PbSO4 + PbS -> Pb + 2SO2 (self-reduction)
- 2Na[Ag(CN)2] + Zn -> Na2[Zn(CN)4] + 2Ag (extraction from leached solution)
- CuSO4(aq) + 2Ag -> Ag2SO4(aq) + Cu (metal displacement method)
Correct answer: 2Na[Ag(CN)2] + Zn -> Na2[Zn(CN)4] + 2Ag (extraction from leached solution)
Solution
Option A: Roasting of PbSO4 would more typically give Pb + SO3 or other products; the given equation is not a standard balanced roasting reaction. Option B: The self-reduction reaction for PbS (not PbSO4) is: PbS + 2PbO -> 3Pb + SO2, or PbS + PbSO4 -> 2Pb + 2SO2. The stated equation mixes PbSO4+PbS but the balancing is off. Option C: This is the correct cementation reaction in the cyanide process for silver: 2Na[Ag(CN)2] + Zn -> Na2[Zn(CN)4] + 2Ag. Zinc displaces silver from the complex. Option D: Cu is more reactive than Ag, so Ag cannot displace Cu from CuSO4. The reaction is non-spontaneous. Correct answer: C.
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