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Question : How is Plaster of Paris prepared? What reaction takes place when it sets to a hard mass?

Answer»

Solution :Plaster of PARIS is PREPARED by heating gypsum to a temperature of `100^@C` . The following reaction takes place
` CaSO_4. 2H_2O overset(100^@C)(to) CaSO_(4) 1/2H_2O+ 1(1)/(2) H_2O`
: On mixing with water, it react to a hard mass to form gypsum again i.e, the REVERSE reaction takes place.


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