Question

Sodium cyanide is used in the extraction of silver from its ore. Explain why it is used and write the relevant equation.

Answer 1

Sodium cyanide is used in the extraction of silver because it forms a soluble complex with silver present in the ore. This process is called cyanide leaching, where silver from its ore (e.g., argentite, Ag₂S) reacts with NaCN in the presence of air (oxygen) to form a soluble complex, sodium dicyanoargentate(I).

\[\ce{Ag2S + 4NaCN + O2 + 2H2O -> 2Na[Ag(CN)2] + 2NaOH + H2SO4}\]

The silver ore reacts with sodium cyanide in the presence of oxygen and water. A soluble complex Na[Ag(CN)₂] is formed. This method helps in the easy separation of silver from the ore in solution form.