Question

Plaster of Paris on making paste with little water sets to hard mass due to formation of

• A. $ CaSO_{4} $
• B. $ CaSO_{4} \cdot 1/2 H_{2}O $
• C. $ CaSO_{4} \cdot H_{2}O $
• D. $ CaSO_{4} \cdot 2H_{2}O $

Answer 1

Answer: (D)

Plaster of Paris becomes very hard by the process of hydration
Plaster of paris is a white powder. It changes into a hard mass called gypsum on mixing with water. There is a slight increase in volume during this process
$\underset{\text{Plaster of Paris}}{{CaSO_{4}\cdot\frac{1}{2}H_{2} O}}+1 \frac{1}{2}H_{2}O \to \underset{\text{Gypsum}}{{CaSO_{4}\cdot2H_{2}O}}+ Heat$