Question

The sum of the number of water molecules in gypsum and plaster of paris is:

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

Answer 1

The correct option is A $\frac{5}{2}$

Molecular formula of gypsum and plaster of paris respectively are $CaS{O}_4.2H_{2}O$ and $CaS{O}_4.\frac{1}{2}{H}_{2}O$
Hence sum of water molecule is $2+\frac{1}{2}=\frac{5}{2}$