Which of the following compounds turns white on treatment with `H_(2)O_(2)`?

Options

A. HgS
B. PbS
C. NiS
D. CuS

Explanation

To determine which of the given compounds turns white upon treatment with hydrogen peroxide (H₂O₂), we will analyze each compound step by step.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds we need to analyze are:
- HgS (Mercury(II) sulfide)
- PbS (Lead(II) sulfide)
- NiS (Nickel(II) sulfide)
- CuS (Copper(II) sulfide)

2. **Reactions with H₂O₂**:
- **For HgS**:
- Reaction:
\[ \text{HgS} + 4 \text{H}_2\text{O}_2 \rightarrow \text{HgSO}_4 + 4 \text{H}_2\text{O} \]
- HgSO₄ is a white crystalline solid. Thus, HgS turns from black to white.

- **For PbS**:
- Reaction:
\[ \text{PbS} + 4 \text{H}_2\text{O}_2 \rightarrow \text{PbSO}_4 + 4 \text{H}_2\text{O} \]
- PbSO₄ is also a white precipitate. Therefore, PbS also turns from black to white.

- **For NiS**:
- Reaction:
\[ \text{NiS} + 4 \text{H}_2\text{O}_2 \rightarrow \text{NiSO}_4 + 4 \text{H}_2\text{O} \]
- NiSO₄ is green in color, so NiS does not turn white.

- **For CuS**:
- Reaction:
\[ \text{CuS} + 4 \text{H}_2\text{O}_2 \rightarrow \text{CuSO}_4 + 4 \text{H}_2\text{O} \]
- CuSO₄ is blue, indicating that CuS does not turn white.

3. **Conclusion**:
- The compounds that turn white upon treatment with H₂O₂ are:
- HgS (turns to HgSO₄, white)
- PbS (turns to PbSO₄, white)
- Therefore, the correct options are **HgS and PbS**.

### Final Answer:
The compounds that turn white on treatment with H₂O₂ are **HgS and PbS**.