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


4M(s) + 8CN (aq)+ 2H2O(aq) + O2(g) 4[M(CN)2] (aq) + 4OH (aq) (M= Ag or Au)


2[M(CN)2]-(aq) +Zn(s) [Zn(CN)4]2-(aq) + 2M(s)


Here the metal M(M=Ag or Au) is displaced from the complex by the action of zinc as a reducing agent.

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