(A) The extraction of gold from its ore involves the formation of the dicyanoaurate$(I)$ complex,$[Au(CN)_2]^-$. To recover metallic gold from this co

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(A) The extraction of gold from its ore involves the formation of the dicyanoaurate$(I)$ complex,$[Au(CN)_2]^-$. To recover metallic gold from this complex,a more electropositive metal like zinc $(Zn)$ is added. The displacement reaction is: $2[Au(CN)_2]^- (aq) + Zn (s) \rightarrow 2Au (s) + [Zn(CN)_4]^{2-} (aq)$.