Which of the following is insoluble in dil `HNO_(3)`

Options

A. `HgS`
B. `PbS`
C. `Bi_(2)S_(3)`
D. `CuS`

Answer

To determine which of the following compounds is insoluble in dilute nitric acid (HNO₃), we will analyze the solubility of each given sulfide:

1. **Identify the compounds**: The compounds we are examining are:
- HgS (Mercuric sulfide)
- PbS (Lead sulfide)
- Bi₂S₃ (Bismuth sulfide)
- CuS (Copper sulfide)

2. **Check the solubility of each compound in dilute HNO₃**:
- **HgS (Mercuric sulfide)**:
- Mercuric sulfide is known to be insoluble in dilute nitric acid. It is only soluble in aqua regia, which is a mixture of hydrochloric acid and nitric acid.

- **PbS (Lead sulfide)**:
- Lead sulfide is soluble in dilute nitric acid. When treated with HNO₃, it dissolves to form lead nitrate.

- **Bi₂S₃ (Bismuth sulfide)**:
- Bismuth sulfide is also soluble in dilute nitric acid. It reacts with HNO₃ to form bismuth nitrate.

- **CuS (Copper sulfide)**:
- Copper sulfide is soluble in dilute nitric acid as well. It reacts with HNO₃ to produce copper nitrate.

3. **Conclusion**:
- Among the given sulfides, the only compound that is insoluble in dilute nitric acid is **HgS (Mercuric sulfide)**.

Thus, the correct answer is **HgS (Mercuric sulfide)**.