What is the number of water of crystallisation molecules present in plaster of Paris?

Correct option is D

The correct answer is: (D)

• The number of water of crystallization molecules present in plaster of Paris is half a molecule of water per formula unit.
• The chemical formula for plaster of Paris is CaSO₄·½H₂O. This means for each formula unit of calcium sulfate (CaSO₄), there is half a molecule of water of crystallization (H₂O)
• Plaster of Paris contains ½ water molecule of crystallization.

Information Booster:

• Plaster of Paris is used in making sculptures, molds, and casts.
•  It sets quickly when mixed with water due to its exothermic reaction.
•  It is also used for coating walls and ceilings as it gives a smooth finish.