Q1. [1]
The water of crystallization is present in
(i) Bleaching Powder
(ii) Plaster of Paris
(iii) Washing Soda
(iv) Baking Soda
- (A) (ii) and (iv)
- (B) (ii) and (iii)
- (C) (i) and (iii)
- (D) (i) and (iv)
Previously asked in CBSE board exam
2025 31/6/1 Q7
Generated by claude-sonnet-4-6 · 2026-06-15 06:45 · grounding rag
Model Answer
(B) (ii) and (iii)
Washing soda (Na₂CO₃·10H₂O) and Plaster of Paris (CaSO₄·½H₂O) both contain water of crystallisation. Bleaching powder and baking soda do not contain water of crystallisation.
Explanation
- Water of crystallisation = fixed number of water molecules in one formula unit of a salt.
- Washing soda: Na₂CO₃·10H₂O ✓
- Plaster of Paris: CaSO₄·½H₂O ✓
- Baking soda (NaHCO₃) and Bleaching powder (CaOCl₂) have no water of crystallisation.
- Examiners expect you to recall the chemical formulae of these common compounds to answer such questions correctly.
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