Coordination Compounds - Result Question 66
####73. $CuSO_4$ when reacts with $KCN$ forms $CuCN$, which is insoluble in water. It is soluble in excess of $KCN$ due to formation of the following complex
[2002]
(a) $K_2[Cu(CN)_4]$
(b) $K_3[Cu(CN)_4]$
(c) $CuCN_2$
(d) $Cu[K Cu(CN)_4]$
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Solution:
- (b) Copper sulphate react with $KCN$ to give white ppt of $Cu(CN)_2$ and cyanogen gas. The insoluble copper cyanide dissolve in excess of $KCN$ and give soluble potassium cuprocyanide
$ \begin{aligned} & CuSO_4+2 KCN \longrightarrow \\ & 2 Cu(CN)_2 \longrightarrow \\ & K_2 SO_4+Cu(CN)_2 \\ & \text{ insoluble } \text{ cyanogen } \end{aligned} $
$ CuCN+3 KCN \longrightarrow K_3[Cu(CN)_4] $
