An aqueous solution is prepared by dissolving a mixture containing `ZnCl_(2),CdCl_(2) and CuCl_(2)`. Now `H_(2)S` gas is passed through the aqueous solution of salt to form precipitate.

Options

A. `CdS`
B. CuS
C. ZnS
D. No ppt.

Answer

To solve the problem, we need to analyze the reactions that occur when hydrogen sulfide (H₂S) gas is passed through the aqueous solution containing the salts ZnCl₂, CdCl₂, and CuCl₂.

### Step-by-Step Solution:

1. **Identify the Compounds**: The mixture contains three salts: Zinc chloride (ZnCl₂), Cadmium chloride (CdCl₂), and Copper(II) chloride (CuCl₂).

2. **Reactions with H₂S**: When H₂S gas is bubbled through the solution, it can react with the metal ions present in the solution to form metal sulfides. The reactions are as follows:
- For Copper(II) chloride (CuCl₂):
\[ \text{Cu}^{2+} + \text{H}_2\text{S} \rightarrow \text{CuS (s)} + 2\text{H}^+ + 2\text{Cl}^- \]
This reaction produces a precipitate of copper sulfide (CuS).

- For Cadmium chloride (CdCl₂):
\[ \text{Cd}^{2+} + \text{H}_2\text{S} \rightarrow \text{CdS (s)} + 2\text{H}^+ + 2\text{Cl}^- \]
This reaction produces a precipitate of cadmium sulfide (CdS).

- For Zinc chloride (ZnCl₂):
\[ \text{Zn}^{2+} + \text{H}_2\text{S} \rightarrow \text{ZnS (s)} + 2\text{H}^+ + 2\text{Cl}^- \]
However, zinc sulfide (ZnS) is not soluble in water, but it does not precipitate under these conditions because it requires a higher concentration of H₂S to form a visible precipitate.

3. **Conclusion**: From the above reactions, we can conclude that:
- Copper(II) sulfide (CuS) and Cadmium sulfide (CdS) will precipitate out of the solution.
- Zinc sulfide (ZnS) does not form a precipitate under these conditions.

4. **Final Answer**: The precipitates formed when H₂S is passed through the aqueous solution are:
- Cadmium sulfide (CdS)
- Copper sulfide (CuS)

### Summary of Precipitates:
- **Precipitates formed**: CuS and CdS
- **No precipitate**: ZnS