Chemistry - Complete s-block Question with Solution | TestHub

The setting of plaster of Paris (calcium sulfate hemihydrate, CaSO₄·½H₂O) is a hydration reaction. It combines with water to form gypsum (calcium sulfate dihydrate, CaSO₄·2H₂O), which is a harder, crystalline solid.

The chemical reaction is:

$$\mathrm{CaS}{\mathrm{O}}_4\cdot \frac{1}{2}{\mathrm{H}}_2\mathrm{O}+\frac{3}{2}{\mathrm{H}}_2\mathrm{O}\to \mathrm{CaS}{\mathrm{O}}_4\cdot 2{\mathrm{H}}_2\mathrm{O}$$