The metal extracted by leaching with cyanide | vedclass

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Question

(D) Leaching is a process used when the ore is soluble in a suitable solvent. In the metallurgy of silver $(Ag)$ and gold $(Au)$,the metal is leached

Vedclass · Accepted Answer

$Ag$

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(D) Leaching is a process used when the ore is soluble in a suitable solvent. In the metallurgy of silver $(Ag)$ and gold $(Au)$,the metal is leached with a dilute solution of $NaCN$ or $KCN$ in the presence of air (for $O_2$). The metal is subsequently recovered by displacement using a more reactive metal like zinc $(Zn)$.The chemical reaction is:$4 M_{(s)} + 8 CN^{-}_{(aq)} + 2 H_2O_{(aq)} + O_{2(g)} \rightarrow 4[M(CN)_2]^{-}_{(aq)} + 4 OH^{-}_{(aq)}$ (where $M = Ag$ or $Au$)Recovery step:$2[M(CN)_2]^{-}_{(aq)} + Zn_{(s)} \rightarrow [Zn(CN)_4]^{2-}_{(aq)} + 2 M_{(s)}$

The metal extracted by leaching with cyanide is

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