When ammonia is added to cupric salt solution, the deep blue colour is observed it is due to the formation of:

Options

A. `[Cu(OH)_(4)]^(2-)`
B. `[Cu(NH_(3))_(4)]^(2+)`
C. `[Cu(H_(2)O)_(2)(NH_(3))_(2)]^(2+)`
D. `[Cu(H_(2)O)_(4)]^(2-)`

Answer

**Step-by-Step Solution:**

1. **Identify the Cupric Salt**: The cupric salt in question is typically copper(II) sulfate, which has the formula CuSO₄.

2. **Add Ammonia**: When ammonia (NH₃) is added to the cupric salt solution, it interacts with the copper ions (Cu²⁺) present in the solution.

3. **Formation of Complex Ion**: Ammonia acts as a ligand. It has a lone pair of electrons that it can donate to the copper ion. When excess ammonia is added, it forms a complex ion, specifically [Cu(NH₃)₄]²⁺.

4. **Color Change**: The formation of the complex ion [Cu(NH₃)₄]²⁺ is responsible for the deep blue color observed in the solution. This deep blue color is characteristic of copper(II) complexes with ammonia.

5. **Conclusion**: Therefore, the deep blue color observed when ammonia is added to the cupric salt solution is due to the formation of the complex ion [Cu(NH₃)₄]²⁺.

**Final Answer**: The deep blue color is due to the formation of the complex ion [Cu(NH₃)₄]²⁺.

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