The sulphide not soluble in hot dilute nitric acid is

Options

A. CuS
B. ZnS
C. CdS
D. HgS

Explanation

To determine which sulphide is not soluble in hot dilute nitric acid, we will analyze the given options: CuS (Copper Sulphide), CdS (Cadmium Sulphide), ZnS (Zinc Sulphide), and HgS (Mercury Sulphide).

### Step-by-step Solution:

1. **Understanding the Solubility of Sulphides**:
- We need to know the general behavior of sulphides when treated with hot dilute nitric acid (HNO3).

2. **Analyzing Each Sulphide**:
- **CuS (Copper Sulphide)**: Copper sulphide is known to be soluble in hot dilute nitric acid.
- **CdS (Cadmium Sulphide)**: Cadmium sulphide is also soluble in hot dilute nitric acid.
- **ZnS (Zinc Sulphide)**: Zinc sulphide is soluble in hot dilute nitric acid as well.
- **HgS (Mercury Sulphide)**: Mercury sulphide is unique among these. It is not soluble in hot dilute nitric acid. Instead, it is soluble only in aqua regia, which is a mixture of nitric acid and hydrochloric acid.

3. **Conclusion**:
- Among the given options, the sulphide that is not soluble in hot dilute nitric acid is **HgS (Mercury Sulphide)**.

### Final Answer:
The sulphide not soluble in hot dilute nitric acid is **HgS (Mercury Sulphide)**.

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