Question

Extraction of gold and silver involves leaching the metal with CN^– ion. The metal is recovered by ______.

Options

• displacement of metal by some other metal from the complex ion.

• roasting of metal complex.

• calcination followed by roasting.

• thermal decomposition of metal complex.

Answer 1

Extraction of gold and silver involves leaching the metal with CN^– ion. The metal is recovered by displacement of metal by some other metal from the complex ion.

Explanation:

The metal in cyanide process is recovered by displacement of metal by some more reactive metal from the complex.

The metal is later recovered by displacement method.

\[\ce{4M + 8CN^{-} + 2H2O + O2  -> 4[M(CN)2]^{-} + 4OH^{-}}\]

\[\ce{2[M(CN)2]^{-} + Zn -> [Zn(CN)4]^{2-} + 2M}\]