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` (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 solve the question, we need to identify the blue compound that crystallizes when an aqueous solution of copper (II) sulfate is saturated with ammonia and then evaporated. Here’s a step-by-step breakdown of the solution:

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

### Step 2: Understand the Reaction
- When copper (II) sulfate is dissolved in water, it dissociates into Cu²⁺ ions and SO₄²⁻ ions.
- When ammonia is added to this solution, it can coordinate with the Cu²⁺ ions to form a complex.

### Step 3: Formation of the Complex
- In the presence of ammonia, the Cu²⁺ ions will form a complex with ammonia. The maximum number of ammonia molecules that can coordinate with Cu²⁺ is four, leading to the formation of the complex [Cu(NH₃)₄]²⁺.
- The sulfate ion (SO₄²⁻) remains as a counter ion in the solution.

### Step 4: Write the Chemical Formula
- The complex formed can be represented as [Cu(NH₃)₄]SO₄.
- When water is also present in the solution, the complete formula for the crystallized compound becomes [Cu(NH₃)₄]SO₄ · 2H₂O, indicating that two water molecules are associated with the complex.

### Step 5: Identify the Color and Structure
- The complex [Cu(NH₃)₄]SO₄ · 2H₂O is known to be blue in color.
- The geometry of the complex is square planar due to the coordination number of 4, which is typical for strong field ligands like ammonia.

### Conclusion
- Therefore, the blue compound that crystallizes on evaporation is [Cu(NH₃)₄]SO₄ · 2H₂O.

### Final Answer
The blue compound that crystallizes on evaporation is **Cu(NH₃)₄SO₄ · 2H₂O**.

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