Question

Which of the following compounds contain water of crystallisation?

• A. Common salt
• B. Gypsum
• C. Plaster of paris
• D. Washing soda

Answer 1

Answer: (B), (C), (D)

The correct options are
B Gypsum
C Plaster of paris
D Washing soda

Water of crystallisation is the fixed number of water molecules present in one formula unit of a salt.
- Chemical formula of common salt is $\text{NaCl}$.
- Chemical formula of gypsum is $CaS{O}_4.2H_{2}O$.
- Chemical formula of plaster of paris is $CaS{O}_4.\frac{1}{2}{H}_{2}O$.
- Chemical formula of washing soda is ${\text{Na}}_2{\text{CO}}_3\cdot 10{\text{H}}_2\text{O}$.
Hence, compounds gypsum, plaster of paris and washing soda have water of crystallisation.