Question

What are the properties of plaster of paris?

Answer 1

1. The Plaster of Paris is synthesized by the reaction between gypsum and water in the presence of heat ($120°\mathrm{C}$). $$\begin{gathered} {\mathrm{CaSO}}_4·\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)+\raisebox{1ex}{$3$}\!\left/ \!\raisebox{-1ex}{$2$}\right.{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\stackrel{∆}{\to }{\mathrm{CaSO}}_4·2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right) \\ \mathrm{Gypsum}\mathrm{Plaster}\mathrm{of}\mathrm{Paris} \end{gathered}$$
2. The material nature is non-combustible and non-flammable.
3. It slowly expands with a slight setting upon it.
4. There is a formation of a hard mass after the drying process without cracks.
5. It has the property to absorb water and form gypsum.
6. During the heating process ($<220°\mathrm{C}$), there is a removal of crystalline water and the formation of dead burnt.