If a aqueous solution of copper (II) sulphate is saturated with ammoina, the blue compound ----- crystallises on evaporation.

Options

A. `[Cu (NH_(3))_(4)]SO_(4) . H_(2)O`
B. `[Cu(NH_(3))_(6)]SO_(4)`
C. `[Cu(NH_(3))_(5)H_(2)O]SO_(4)`
D. `[Cu(H_(2)O)_(2)(NH_(3))_(4)]SO_(4)`

Answer

A

Explanation

With ammonia solution, it forms the soluble blue complex. First it forms a precipitate of `Cu(OH)_(2)` which dissolves in excess of ammonia solution:
`CuSO_(4) + 2NH_(4)OH rarr Cu(OH)_(2) + (NH_(4)) SO_(4)`
`Cu(OH)_(2) + 2NH_(4)OH + (NH_(4))_(2)SO_(4) rarr [Cu(NH_(3))_(4)]SO_(4) + 4H_(2)O`