Statement I : Leaching of gold with cyanide ion in absence of air / O2 leads to cyano complex of Au(III).
Statement II : Zinc is oxidized during the displacement reaction carried out for gold extraction.
In the light of the above statements, choose the correct answer from the options given below.
Solution
Leaching of gold with cyanide ion is done in
presence of air/O<sub>2</sub> leading to cyano complex [Au(CN)<sub>2</sub>]<sup>–</sup> where Au is in +1 oxidation state.<br/><br/>
4Au(s) + 8CN<sup>–</sup>(aq) + 2H<sub>2</sub>O(aq) + O<sub>2</sub>(g) $$\longrightarrow 4\left[\mathrm{Au}(\mathrm{CN})_{2}\right]_{\mathrm{aq}}^{-}+4 \mathrm{OH}^{-}$$<br/><br/>
$$\begin{aligned} 2\left[\mathrm{Au}(\mathrm{CN})_{2}\right]_{(\mathrm{aq})}^{-} &+\mathrm{Zn}(\mathrm{s}) \\ & \longrightarrow\left[\mathrm{Zn}(\mathrm{CN})_{4}\right]_{(\mathrm{aq})}^{2-}+2 \mathrm{Au}(\mathrm{s}) \end{aligned}$$<br/><br/>
Zinc is oxidised from (0) to +2 oxidation state during
displacement reaction carried out for gold
extraction.
About this question
Subject: Chemistry · Chapter: p-Block Elements · Topic: Group 13: Boron Family
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