Write the chemical name of Plaster of Paris. Write the chemical equation of its preparation. Why should Plaster of Paris be stored in a dry place ?

Explanation

Chemical name of Plaster of Paris is calcium sulphate hemihydrate and its formula is `CaSO_(4). 1/2 H_(2)O`.
Preparation :
`underset("Gypsum")(CaSO_(4).2H_(2)O) overset("Heat")(rarr) underset("Plaster of Paris")(CaSO_(4). 1/2 H_(2)O+1 1/2 H_(2)O)`
In the presence of moisture the Plaster of Paris powder changes to a hard solid mass called gypsm, so it has to be stored in a dry place.