Question

Write the principle involved in the following: Recovery of silver after silver ore was leached with NaCN.

Answer 1

Role of NaCN in the extraction of silver (Ag) is to do the leaching of Ag ore in the presence of air from which the silver is obtained later by replacement.

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

Answer 2

In the process of leaching of silver, Ag is treated with sodium cyanide. The solution of sodium cyanide oxidizes Ag in to Ag+ .

Then this Ag+ combines with the cyanide ions present in the solution and forms a soluble complex [Ag(CN)2]- .

Through the soluble complex formed the silver is recovered through displacement method, by using more electropositive Zinc.

The process of leaching is also known as process of extraction in chemical industry. It is a process of extracting a substance from a solid material dissolved in a liquid.