Q.Which of the following metals is extracted by leaching the ore with dilute cyanide solution ?

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 …