Which one of the following reactions is an example of auto-reduction?

Options

A. `Fe_(3)O_(4)+4CO to 3Fe+4CO_(2)`
B. `Cu_(2)O+C to 2Cu+ CO `
C. `Cu^(2+)(aq)+Fe(s) to Cu(s)+Fe^(2+)(aq)`
D. `Cu_(2)O+(1)/(2)Cu_(2)S to 3Cu+(1)/(2)SO_(2)`

Answer

D

Explanation

Auto-reduction is also known as self-reduction . This is used when no external reducing agent is required. The sulphide ores of less electropositive metal like Hg, Pb, Cu etc., are heated in air to convert a part of the ore into oxide or sulphide which then reacts with the remaining sulphide ore to given the metal and sulphur dioxide , e.g., `Cu_(2)O+(1)/(2)Cu_(2)S to 3Cu+(1)/(2)SO_(2)`