Ammonia is used in detection of `Cu^(2+)` ion because

Options

A. 1. aqueous solution of `NH_(3)` reacts with `Cu^(2+)` ion to form deep blue coloured complex
B. 2. `NH_(3)` reacts with `Cu^(2+)` ion to give blue precipitate of CuO
C. 3. aqueous solution of `NH_(3)` reacts with `Cu^(2+)` ion to form white coloured complex
D. 4. `NH_(3)` reacts with `Cu_(2+)` ion to give green precipitate.

Explanation

To answer the question "Ammonia is used in detection of `Cu^(2+)` ion because...", we can break down the solution step by step:

### Step 1: Understanding Ammonia
Ammonia (NH₃) is a compound that acts as a Lewis base. A Lewis base is defined as a substance that can donate a pair of electrons to form a covalent bond. In the case of ammonia, the nitrogen atom has a lone pair of electrons that can be donated.

**Hint:** Remember that Lewis bases have lone pairs of electrons that can be shared with other species.

### Step 2: Reaction with Copper Ions
When ammonia is introduced to a solution containing copper ions, specifically Cu²⁺ (copper(II) ions), it forms a complex. The reaction involves the formation of a deep blue-colored complex due to the interaction between the lone pair of electrons from ammonia and the Cu²⁺ ion.

**Hint:** The color change is a key indicator of the reaction taking place.

### Step 3: Formation of Copper Hydroxide
Initially, when ammonia is added to a solution of copper(II) chloride (CuCl₂), it can lead to the formation of copper(II) hydroxide (Cu(OH)₂), which is a light blue precipitate. This reaction can be represented as:
\[ \text{CuCl}_2 + 2 \text{NH}_3 + 2 \text{H}_2\text{O} \rightarrow \text{Cu(OH)}_2 + 2 \text{NH}_4^+ + 2 \text{Cl}^- \]

**Hint:** Pay attention to the precipitate formed; it indicates the initial reaction before the complex forms.

### Step 4: Formation of the Deep Blue Complex
When excess ammonia is added to the light blue precipitate of copper(II) hydroxide, the copper ions go back into the solution and form a deep blue complex, specifically [Cu(NH₃)₄]²⁺. This deep blue color is a definitive indicator of the presence of Cu²⁺ ions.

**Hint:** The deep blue color is a hallmark of the complex formed with ammonia.

### Step 5: Conclusion
Thus, ammonia is used in the detection of Cu²⁺ ions because it forms a deep blue complex with the copper ions, which can be visually identified. The presence of this complex indicates the presence of Cu²⁺ in the solution.

**Final Answer:** Ammonia is used in the detection of Cu²⁺ ion because it forms a deep blue complex with the ion, indicating its presence.