State what happens when:
$(a)$ Gypsum is heated at $373 \, K$.
Also,write the chemical equation for the reaction.

(N/A) When gypsum $(CaSO_4 \cdot 2H_2O)$ is heated at $373 \, K$,it loses three-fourths of its water of crystallization and forms Plaster of Paris $(CaSO_4 \cdot \frac{1}{2}H_2O)$.
The chemical equation for this reaction is:
$CaSO_4 \cdot 2H_2O(s) \xrightarrow{373 \, K} CaSO_4 \cdot \frac{1}{2}H_2O(s) + 1\frac{1}{2}H_2O(g)$