Extraction of gold and silver involves leaching the metal with CN- ion. The metal is recovered by

Extraction of gold and silver involves leaching the metal with CN- ion. The metal is recovered by displacement of metal by some other metal from the complex ion. This is an oxidation reaction.4Au(s)+8CN(aq)+2H2O(aq)+O2(g)⟶4Au(CN)2−(aq)+4OH−(aq)4Au(CN)2−(aq)+Zn(s)⟶2Au(s)+Zn(CN)42−(aq)Here, Zn acts as a reducing agent.