Copper sulphate solution reacts with `KCN` to give
(a) `Cu(CN)_(2)`
(b) `CuCN`
(c ) `K_(2)[Cu(CN)_(4)]`
(d) `K_(3)[Cu(CN)_(4)]` .

Options

A. `Cu (CN)_(2)`
B. `Cu CN`
C. `K_(2)[Cu CN)_(4)]`
D. `K_(3)[Cu(CN)_(4)]`

Answer

D

Explanation

Copper suophate when reacts `KCN` first gives precipiated of cupric cyanide which reduces into `Cu_(2) CN_(2)` and dissolves in excess of `KCN` to gives soluble `K_(3) [Cu(CN)_(4)]` complex salt.
`[CuSO_(4) + 2KCN rarr underset("Cupric cyanide")Cu(CN)_(2) + K_(2)SO_(4)]xx 2`
`2Cu(CN)_(2) rarr Cu_(2) +underset("cyanogen")(NC-CN)`
`Cu_(2) (CN)_(2) + 6KCN rarr underset("Soluble complex salt")(2K_(3) [Cu(CN)_(4)])`
`bar(2CuSO_(4) + 10 KCN rarr 2K_(3) [Cu(CN)_(4)] +2K_(2)SO_(4) +(CN)_(2)`