1.

Write the chemical reactions involved in the process of extraction of Gold. Explain the role of dilute NaCN and Zn in this process.

Answer»

Solution :Gold is leached with a dilute solution of NaCN or KCN in the PRESSENCE of air (for `O_2`) from which the metal is OBTAINED later by replacement.
`4Cu (s) +8CN^(-) (aq) +2H_(2)O (aq) +O_(2)(g) to 4[Au(CN)_(2)]^(-) (aq) +4OH^(-) (aq)`
`2[Au(CN)_(2)]^(-) (aq) +Zn (s) to [Zn(CN)_(4)]^(2-) (aq) +2Au (s)`
NaCN or KCN ACTS as LEACHING agent and zinc acts as precipitating agent to precipitate gold.


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