Question

Copper sulphate when dissolved in exess of KCN gives.
a) Cu(CN)₂b) [Cu(CN)₄]³⁻c) [Cu(CN)₄]²⁻d) CuCN

Answer 1

hey mate...........
"C" option is correct..

Answer 2

c) [Cu(CN)₄]²⁻.

First cupric cyanide is formed, Cu(CN)2 and Cupric Cyanide will decompose to produce cuprous cyanide, Cu2CN2.

With Cuprous cyanide reacts with excess of KCN to form a complex, K3[Cu(CN)4] which is a stable complex.

CuSO4 decolourises on the KCN, as product is Cu2+ get reduced to form in the system.