Write equations to represent the following observations: When NaOH is added to aqueous `CuSO_(4)` solutin, a pale blue precipitate is formed. On adding aqeous `NH_(3)` solution, When NaOH is added to give a deep blue solution. If the solution is made acidic with dilute `HNO_(3)`, the colour is converted back to pale blue solution.

Explanation

`Cu^(2+)(aq) + 2OH^(-)(aq) to Cu(OH)_(2)(g)`
`Cu(OH)_(2)(s) + 4NH_(3)(aq) to [Cu(NH_(3))_(4)]^(2+)(aq) + 2OH^(-) (aq)`
`[Cu(NH_(3))_(4)]^(2+) (aq) + 4H_(3)O^(+) to [Cu(OH)_(4)]^(2+) + 4NH_(4)^(+) (aq)`