Sulphides of which of the metals is/are soluble in water.

Options

A. Na
B. K
C. Zn
D. Cu

Explanation

To determine which sulfides of the given metals are soluble in water, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Metals and Their Sulfides**:
- The metals given are sodium (Na), potassium (K), zinc (Zn), and copper (Cu).
- The corresponding sulfides are:
- Sodium sulfide (Na₂S)
- Potassium sulfide (K₂S)
- Zinc sulfide (ZnS)
- Copper sulfide (CuS)

2. **Understand the Concept of Solubility**:
- For a compound to be soluble in water, the hydration energy (energy released when the compound dissolves in water) must be greater than the lattice energy (energy required to separate the ions in the solid compound).

3. **Analyze the Hydration and Lattice Energies**:
- For sodium sulfide (Na₂S) and potassium sulfide (K₂S):
- The hydration energy is greater than the lattice energy, which means Na₂S and K₂S are soluble in water.
- For zinc sulfide (ZnS) and copper sulfide (CuS):
- The hydration energy is less than the lattice energy, indicating that ZnS and CuS are not soluble in water.

4. **Conclusion**:
- The sulfides that are soluble in water are:
- Sodium sulfide (Na₂S)
- Potassium sulfide (K₂S)
- Therefore, the answer is that the sulfides of sodium and potassium are soluble in water.

### Final Answer:
Sulfides of sodium (Na₂S) and potassium (K₂S) are soluble in water.

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