Chemistry - Coordination Chemistry Question with Solution | TestHub

The reaction of CuSO₄ with KCN proceeds in two steps. First, CuCN precipitates. With excess KCN, CuCN dissolves to form a stable tetracyanocuprate(I) complex.

Reaction:

$$2{\mathrm{CuSO}}_4+4\mathrm{KCN}\to 2\mathrm{CuCN}\downarrow +2{\mathrm{K}}_2{\mathrm{SO}}_4+(\mathrm{CN}{)}_2$$

$$2\mathrm{CuCN}+6\mathrm{KCN}\to 2{\mathrm{K}}_3[\mathrm{Cu}(\mathrm{CN}{)}_4]$$

The final product is ${\mathrm{K}}_3[\mathrm{Cu}(\mathrm{CN}{)}_4]$.