CGPET 2013 Solved Paper

Gypsum is a very soft sulphate mineral composed of calcium sulphate dihydrate, with the chemical formula CaSO4⋅2H2O.
On heating, gypsum loses water and gives the hemihydrate (CaSO4⋅‌

1

2

H2O) or the anhydrite.

2CaSO4⋅2H2O

gypsum

120∘C

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(CuSO4)2⋅H2O+3H2O

plaster‌of‌Paris(Calcium‌sulphate‌hemihydrate)

The hemihydrate is known as calcined gypsum or plaster of Paris.