Chemistry Question on General Principles and Processes of Isolation of Elements

Question

This metal is extracted from its ore by formation of a cyanide complex

Answer 1

Solution

Gold (Au) and silver (Ag) are extracted by treating their ores with dilute NaCN solution in the presence of air. During this process, a cyanide complex is formed which gives pure metal when treated with more electropositive metal like $Z n$ .
$4 Ag +8 CN ^{-}+2 H _{2} O + O _{2}$
$\longrightarrow 4\left[ Ag ( CN )_{2}\right]^{-}+4 OH ^{-}$
$2\left[ Ag ( CN )_{2}\right]^{-}+ Zn \longrightarrow\left[ Zn ( CN )_{4}\right]^{2-}+\underset{\text{silver}}{2 Ag}$
This process is called Mac Arthur Forest process.