Which of the following salts does not contain water of crystallisation?

Options

A. Blue vitriol
B. Baking soda
C. washing soda
D. Gypsum

Explanation

To determine which of the following salts does not contain water of crystallization, we need to analyze the chemical formulas of the given salts.

1. **Identify the Salts**: The salts mentioned in the question are:
- Blue vitriol (Copper(II) sulfate pentahydrate)
- Baking soda (Sodium bicarbonate)
- Washing soda (Sodium carbonate decahydrate)
- Gypsum (Calcium sulfate dihydrate)

2. **Examine Each Salt for Water of Crystallization**:
- **Blue Vitriol**: The chemical formula is CuSO4·5H2O. This indicates that it contains 5 molecules of water of crystallization.
- **Baking Soda**: The chemical formula is NaHCO3. There are no water molecules associated with this compound, indicating that it does not contain water of crystallization.
- **Washing Soda**: The chemical formula is Na2CO3·10H2O. This shows that it contains 10 molecules of water of crystallization.
- **Gypsum**: The chemical formula is CaSO4·2H2O. This means it contains 2 molecules of water of crystallization.

3. **Conclusion**: Among the salts listed, baking soda (NaHCO3) is the only one that does not contain any water of crystallization.

Thus, the answer to the question is **Baking Soda (NaHCO3)**.