(i) Fe3O4 + 4CO → 3Fe + 4CO2
(ii) Cu2O + C → 2Cu + CO
(iii) Cu2+ (aq) + Fe (s) → Cu (s) + Fe2+ (aq)
(iv) Cu2O + 1/2Cu2S → 3Cu + 1/2SO2
Correct Answer: (iv) Cu2O + 1/2Cu2S → 3Cu + 1/2SO2
Explanation: Sulphide ores of certain metals such as Hg, Pb and Cu if heated in the air they bring about the conversion of part of the metal sulphide into oxide or sulphate and then react with the remaining sulphide to give matte SO2. Reducing agent is not used in this process.
Reaction Involved:
2Cu2S+3O2→2Cu2O+3SO2
2Cu2O+Cu2S→6Cu+SO2