Ncert Exercises & Solutions

Write the chemical reactions involved in the extraction of gold by cyanide process. Also give the role of zinc in the extraction.

NEETprep Answer:

(i) 4 A u (s) + 8 C N^{-} (a q) + 2 H_{2} O (a q) + O_{2} (g) \to 4 {[Au {(CN)}_{2}]}^{-} (aq) + 4 {OH}^{-} (aq)

(ii) 2 {[Au {(CN)}_{2}]}^{-} (aq) + Zn (s) \to 2 Au (s) + {[Zn {(CN)}_{4}]}^{2 -} (aq)

Zinc acts as a reducing agent in this reaction.