Which of the anhydrous salts when come in contact with water turns blue

Options

A. Ferrous sulphate
B. Copper sulphate
C. Znic sulphate
D. Cobalt sulphate

Explanation

To determine which anhydrous salt turns blue when it comes in contact with water, we will analyze the behavior of various salts when dissolved in water.

### Step-by-Step Solution:

1. **Identify the Salts**: The salts we will consider include ferrous sulfate (FeSO4), copper sulfate (CuSO4), zinc sulfate (ZnSO4), and cobalt sulfate (CoSO4).

2. **Analyze Ferrous Sulfate (FeSO4)**:
- When FeSO4 is dissolved in water, it forms a solution that is orange-red in color due to the presence of Fe²⁺ ions.
- **Conclusion**: FeSO4 does not turn blue.

3. **Analyze Copper Sulfate (CuSO4)**:
- When CuSO4 is dissolved in water, it forms a blue solution because of the Cu²⁺ ions.
- **Conclusion**: CuSO4 turns blue when it comes in contact with water.

4. **Analyze Zinc Sulfate (ZnSO4)**:
- When ZnSO4 is dissolved in water, it forms a colorless solution.
- **Conclusion**: ZnSO4 does not turn blue.

5. **Analyze Cobalt Sulfate (CoSO4)**:
- When CoSO4 is dissolved in water, it forms a solution that is olive or grey in color.
- **Conclusion**: CoSO4 does not turn blue.

### Final Answer:
The anhydrous salt that turns blue when it comes in contact with water is **Copper Sulfate (CuSO4)**.