Q.Cyanide process is used for the extraction of which of the following metals?

Silver is extracted by dissolving its ore in dilute cyanide solution and then displacing the metal with zinc.

In the cyanide (hydrometallurgical) process, silver ore is treated with a dilute solution of sodium or potassium cyanide in the presence of air:

4 Ag + 8 CN- + 2 H2O + O2 -> 4 [Ag(CN)2]- + 4 OH-

The soluble dicyanoargentate(I) complex is then reduced by a more electropositive metal (zinc):

2 [Ag(CN)2]- + Zn -> [Zn(CN)4]2- + 2 Ag …

The cyanide process is used to extract silver (and gold) — option (B).

In the cyanide (leaching) process, the crushed ore is treated with a dilute solution of sodium cyanide in the presence of air. Silver dissolves as a soluble complex:

4Ag + 8NaCN + 2H2O + O2 → 4Na[Ag(CN)2] + 4NaOH

The silver is then displaced from the complex by adding a more reactive metal such as zinc:

2Na[Ag(CN)2] + Zn → Na2[Zn(CN)4] + 2Ag …