Write the chemical reactions involved in the extraction of gold by the cyanide process. Also,explain the role of zinc in this extraction.

(N/A) The extraction of gold involves the following steps:
$1$. Leaching: Gold is treated with a dilute solution of sodium cyanide $(NaCN)$ in the presence of air $(O_2)$ to form a soluble complex:
$4 Au(s) + 8 CN^{-}(aq) + 2 H_{2}O(l) + O_{2}(g) \rightarrow 4 [Au(CN)_{2}]^{-}(aq) + 4 OH^{-}(aq)$
$2$. Reduction: The gold is recovered from the complex by adding zinc $(Zn)$,which acts as a reducing agent:
$2 [Au(CN)_{2}]^{-}(aq) + Zn(s) \rightarrow 2 Au(s) + [Zn(CN)_{4}]^{2-}(aq)$
Zinc acts as a reducing agent by displacing gold from its complex.