Question

Write the chemical reaction for the change of Gypsum into Plaster of Paris.

Answer 1

1. Gypsum is the dihydrate form of Calcium sulfate(CaSO₄.2H₂O) that is a white hard solid substance.
2. Plaster of Paris(POP) is the semihydrate form of Calcium sulphate $\left({\mathrm{CaSO}}_4·\frac{1}{2}{\mathrm{H}}_2\mathrm{O}\right)$ that is in the form of a white powder.

When Gypsum is converted into POP the following reaction takes place:-

$\underset{Gypsum}{{\mathrm{CaSO}}_4·2{\mathrm{H}}_2\mathrm{O}}\stackrel{373\mathrm{K}\mathrm{or}100°\mathrm{C}}{\to }\mathrm{C}\underset{\mathrm{Plaster}\mathrm{of}\mathrm{Paris}}{{\mathrm{aSO}}_4·\frac{1}{2}{\mathrm{H}}_2\mathrm{O}}+1\frac{1}{2}{\mathrm{H}}_2\mathrm{O}$