What is the coordination entity formed when excess of aqueous KCN is added to an aqueous solution of copper sulphate?

Options

A. `CuCN`
B. `K_3[Cu(CN)_6]`
C. `K[Cu(CN)_4]`
D. `K_3[Cu(CN)_4]`

Answer

D

Explanation

When excess of KCN(aq) is mixed with `CuSO_4(aq)`, a complex named potassium tetracyanocuprate (II) is formed. Since , `CN^(-)` ions are strong ligands, the complex is quite stable.
`2Cu^(2+) + 2CN^(-) to 2Cu^(+) + C_2N_2 , 2Cu^(+) + 2CN^(-) to 2CuCN`
`CuCN + 3CN^(-) to [Cu(CN)_4]^(3-)`