Extraction of gold and silver involves leachi | vedclass

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(A) The extraction of gold and silver involves the formation of a soluble complex with $CN^{-}$ ions in the presence of air $(O_2)$.$4Au(s) + 8CN^{-}(

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Displacement of metal by some other metal from the complex ion

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(A) The extraction of gold and silver involves the formation of a soluble complex with $CN^{-}$ ions in the presence of air $(O_2)$.$4Au(s) + 8CN^{-}(aq) + 2H_2O(aq) + O_2(g) \rightarrow 4[Au(CN)_2]^{-}(aq) + 4OH^{-}(aq)$$2Ag(s) + 4CN^{-}(aq) + 2H_2O(aq) + O_2(g) \rightarrow 2[Ag(CN)_2]^{-}(aq) + 4OH^{-}(aq)$The metal is then recovered from the complex by displacement using a more electropositive metal like zinc $(Zn)$:$2[Au(CN)_2]^{-}(aq) + Zn(s) \rightarrow [Zn(CN)_4]^{2-}(aq) + 2Au(s)$$2[Ag(CN)_2]^{-}(aq) + Zn(s) \rightarrow [Zn(CN)_4]^{2-}(aq) + 2Ag(s)$Thus,the correct method is the displacement of the metal by some other metal from the complex ion.

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

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