Question

Which one of the following salts does not contain water of crystallization?
1. Baking soda
2. Blue vitriol
3. Washing soda
4. Gypsum

Answer 1

Correct Answer - Option 1 : Baking soda

Baking soda is NOT correct.

• Baking soda is sodium bicarbonate.
• The chemical formula of baking soda is NaHCO₃.
• The chemical formula of baking soda does not contain any water molecule(H₂O) hence it is clear that It does not contain any water of crystallisation.
• Baking soda is widely used as dry fire extinguisher because of its alkali nature.
• Baking soda consists of sodium cation(Na⁺) and a bicarbonate anion (HCO₃^-).
• It reacts immediately with acids.

• The chemical formula of all three salts below contains water molecule(H₂O) hence it is clear that It contains water of crystallisation.
• Chemical formula of blue vitriol is CuSO₄ .5H₂O.
• Chemical formula of washing soda Na₂CO₃ .10H₂O.
• Chemical formula of gypsum CaSO₄ 2H₂0.