When Plaster of Paris is mixed with water and applied on a fractured limb it becomes a hard mass. Explain with a balanced chemical equation.

It is converted into Gypsum due to the moisture present in the atmosphere.

$CaS{O}_4\cdot \frac{1}{2}{H}_{2}O+\frac{3}{2}{H}_{2}O\to CaS{O}_4\cdot 2H_{2}O$

(Plaster of Paris)                              (Gypsum)