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The extraction of Au by leaching with Na...

The extraction of Au by leaching with NaCN involves both oxidation and reduction.Justify by giving equation.

Text Solution

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`4Au(s)+8CN^(-)(aq)+2H_(2)O(aq)+O_(2)(g)to4[Au(CN)_(2)]^(-)(aq)+4OH^(-)(aq)`
`2[Au(CN)_(2)]^(-)(aq)+Zn(s)to2Au(s)+[Zn(CN)_(4)]^(-2)(aq)`
In the first reaction Au changes into `Au^(+)`,i.e its oxidation takes place.In the second reaction:
`Au^(+)toAu^(@)` (i.e) reduction takes place.
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