Extraction of gold and silber involves leaching the metal with `CN^(-)` ion. The metal is recovered by _______ .

Options

A. displacement of metal by some other metal from the complex ion.
B. roasting of metal complex.
C. calcination followed by roasting.
D. thermal decomposition of metal complex.

Answer

A

Explanation

`2[Ag(CN)_2]^(-) + Zn to 2Ag + [Zn(CN)_4]^(2-) , " " 2[Au(CN)_2]^(-) + Zn to Au + [ Zn(CN)_4 ]^(2-)`