Question

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

Answer 1

$Au\left(s\right)+8C{N}^{-}\left(aq\right)+2H_{2}O\left(aq\right)+O_2\left(g\right)\to 4\left[Au\right(CN{)}_2\left]\right(aq)+40H^{-}(aq)$

$2\left[Au\right(CN{)}_2\left]\right(aq)+Zn(s)\to 2Au(s)+[Zn\left(CN{)}_2\right]\left(aq\right)$

NaCN acts as leaching agent and Zn acts as reducing agent.