In qualitative analysis when `H_(2)S` is passed through an aqueous solution of salt acidified with dil. HCl, a black precipitate is obtained. On boiling the precipitate with dil. `HNO_(3)`, it forms a solution of blue colour. Addition of excess of aqueous solution of ammonia to this solution gives

Options

A. 1. deep blue precipitate of `Cu(OH)_(2)`
B. 2. deep blue solution of `[Cu(NH_(3))_(4)]^(2+)`
C. 3. deep blue solution of `Cu(NO_(3))_(2)`
D. 4. deep blue solution of `Cu(OH)_(2).Cu(NO_(3))_(2)`

Explanation

To solve the given problem step by step, we will analyze the reactions involved and the resulting products.

### Step 1: Identify the Reaction with H₂S
When hydrogen sulfide (H₂S) is passed through an aqueous solution of a salt that is acidified with dilute hydrochloric acid (HCl), a black precipitate is formed. This black precipitate is likely copper sulfide (CuS), which is formed when H₂S reacts with copper(II) ions (Cu²⁺) from copper sulfate (CuSO₄).

**Reaction:**
\[ \text{CuSO}_4 + \text{H}_2\text{S} \rightarrow \text{CuS (black precipitate)} + \text{H}_2\text{SO}_4 \]

### Step 2: Boiling with Dilute HNO₃
When the black precipitate (CuS) is boiled with dilute nitric acid (HNO₃), it dissolves to form a blue solution of copper(II) nitrate (Cu(NO₃)₂).

**Reaction:**
\[ \text{CuS} + 2 \text{HNO}_3 \rightarrow \text{Cu(NO}_3\text{)}_2 + \text{H}_2\text{S} \]

### Step 3: Addition of Excess Aqueous Ammonia
When excess aqueous ammonia (NH₃) is added to the blue solution of copper(II) nitrate (Cu(NO₃)₂), a complex ion is formed. The ammonia reacts with copper(II) ions to form tetraamminecopper(II) complex, which is deep blue in color.

**Reaction:**
\[ \text{Cu(NO}_3\text{)}_2 + 4 \text{NH}_3 \rightarrow \text{Cu(NH}_3\text{)}_4^{2+} + 2 \text{NO}_3^{-} \]

### Conclusion
The final product after adding excess aqueous ammonia to the blue solution is the deep blue solution of the tetraamminecopper(II) complex, \(\text{Cu(NH}_3\text{)}_4^{2+}\).

### Final Answer
The addition of excess aqueous solution of ammonia to the blue solution gives a deep blue solution of \(\text{Cu(NH}_3\text{)}_4^{2+}\).

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