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

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

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In extraction of gold by cyanide process, gold particles present in the ore are treated with a dilute solution of NaCN in the presence of atmospheric oxygen. Gold particles dissolve by forming complex cyanide that is soluble in nature.

4Au+8NaCN+2H_{2}O+O_{2}\rightarrow 4Na[Au(CN)_{2}]+4NaOH

On adding electropositive metal like zinc Au is recovered from solution.

2Na [Au(CN)_{2}]+Zn\rightarrow Na_{2}[Zn(CN)_{4}]+2Au

The process of extraction of gold by cyanide oxidation as well as reduction. oxidation of gold takes place during the formation of cyanide complex whereas reduction takes place during its recovery. Zn acts as a reducing agent.

 

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