Question

The difference in number of crystalline water molecules in a molecule of gypsum and a molecule of plaster of Paris is

• A. $\frac{5}{2}$
• B. $2$
• C. $\frac{1}{2}$
• D. $\frac{3}{2}$

Answer 1

The correct option is D $\frac{3}{2}$

Gypsum is calcium sulfate dihydrate.
Plaster of Paris is calcium sulfate hemihydrate
The difference in number of crystalline water molecules in a molecule of gypsum and a molecule of plaster of Paris is $2-\frac{1}{2}=\frac{3}{2}$.