When an aqueous solution of copper (II) sulphate is saturated with ammonia, the blue compound crystallises on evaporation. The formula of this blue compound is:

Options

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

Answer

To determine the formula of the blue compound that crystallizes when an aqueous solution of copper (II) sulfate is saturated with ammonia, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**: The reactants in this scenario are copper (II) sulfate (CuSO₄) and ammonia (NH₃).

2. **Understand the Reaction**: When copper (II) sulfate is mixed with ammonia, it forms a complex. The ammonia acts as a ligand and coordinates with the copper ions.

3. **Write the Reaction**: The reaction can be represented as:
\[ \text{CuSO}_4 + \text{NH}_3 \rightarrow \text{[Cu(NH}_3\text{)}_4]^{2+} + \text{SO}_4^{2-} \]
Here, the copper ion (Cu²⁺) coordinates with four ammonia molecules to form a complex ion.

4. **Determine the Blue Compound**: The complex formed is tetraamminecopper(II) sulfate, which can be represented as:
\[ \text{[Cu(NH}_3\text{)}_4]\text{SO}_4 \]
This compound is blue in color.

5. **Final Formula**: The formula of the blue compound that crystallizes upon evaporation is:
\[ \text{Cu(NH}_3\text{)}_4\text{SO}_4 \cdot \text{H}_2\text{O} \]
This indicates that the compound may also contain water of crystallization.

### Conclusion:
The blue compound formed when an aqueous solution of copper (II) sulfate is saturated with ammonia is \(\text{Cu(NH}_3\text{)}_4\text{SO}_4 \cdot \text{H}_2\text{O}\).