Hey there! The answer and explanation is below.
Tip: Plaster of Paris on reaction with water to give gypsum.
Plaster of Paris is nothing but calcium salt. It consists of water of crystallization. This is known as the calcium sulphate hemihydrate.
In reaction with water it gives gypsum which is the hydrated salt of calcium sulphate. The reaction is carried out exactly at 373 Kelvin. It needs 2.5 moles of water to form gypsum.
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