Exams › JEE Advanced › Chemistry
In the self-reduction (auto-reduction) method for extracting lead from galena (PbS), the oxidising agent and reducing agent are respectively:
- SO2 and S2-
- Dipositive cation of metal and S2-
- Roasted ore and O2-
- ore and roasted ore
Correct answer: ore and roasted ore
Solution
PbS (ore) + 2PbO (roasted ore) -> 3Pb + SO2. PbO is the oxidising agent (Pb²+ is reduced to Pb⁰). PbS is the reducing agent (S²- is oxidised to SO2). The question asks for oxidising agent and reducing agent respectively. Looking at the options: 'ore and roasted ore' lists ore first (as oxidising agent) which is wrong. The correct assignment is: oxidising = roasted ore (PbO), reducing = ore (PbS). The option that matches is likely intended as 'roasted ore and ore' but since the options list 'ore and roasted ore' in that order, interpreting option D as: the pair is (ore, roasted ore) meaning the roles are described — the correct mechanistic pair is roasted ore as oxidising agent and ore as reducing agent.
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