A white metal sulphide soluble in water is

Options

A. `CuS`
B. `Na_(2)S`
C. `PbS`
D. `ZnS`

Explanation

To solve the question "A white metal sulphide soluble in water is," we can follow these steps:

### Step 1: Identify the options
The given options are:
1. Copper sulphide
2. Sodium sulphide
3. Lead sulphide
4. Zinc sulphide

### Step 2: Analyze the solubility of each option
- **Copper sulphide (CuS)**: This is generally insoluble in water.
- **Sodium sulphide (Na2S)**: This is soluble in water as it is an alkali metal salt.
- **Lead sulphide (PbS)**: This is also insoluble in water.
- **Zinc sulphide (ZnS)**: This is typically insoluble in water.

### Step 3: Determine the color of each sulphide
- **Copper sulphide**: Usually black.
- **Sodium sulphide**: This is a white solid.
- **Lead sulphide**: Usually black.
- **Zinc sulphide**: This is white but is not soluble in water.

### Step 4: Conclusion
From the analysis, the only sulphide that is both white and soluble in water is **sodium sulphide (Na2S)**.

### Final Answer
The white metal sulphide soluble in water is **sodium sulphide (Na2S)**.

---