Question

Why is calcium sulphate hemihydrate called plaster of paris 0?

Answer 1

Calcium Sulphate (Plaster of paris)
it is a hemihydrate of calcium sulphate.it is obtained when gypsum, CaSO4 2 H2O,is heated to 393 K.
2(CaSO4.2H2O).... 2(CaSO4).H2O +3 H2O

above 393 K, no water of crystallisation is left and anhydrous calcium sulphate,CaSO4 is formed. this is known as 'dead burnt plaster'.

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Answer 2

$<b>$ Because, :- Plaster of Paris (POP) is obtained by heating calcium sulphate hemi hydrate, also referred as gypsum for about 140-180 degree Celsius. The name Plaster of Paris (POP) is derived as the calcium sulphate hemi hydrates are found in large amount deposited in the Montmartre hill in Paris.