Dead burnt plaster is ………….

1.	Dead burnt plaster is ………….
Answer» `CaSO_(4)` `CaSO_(4)(1)/(2)H_(2)O` `CaSO_(4)2H_(2)O` `CaSO_(4)2H_(2)O` Solution :Plaster of paris on HEATING at `200^(@)C` changes into anhydrous `CaSO_(4)`. `2CaSO_(4)2H_(2)O to (CaSO_(4))_(2)(1)/(2)H_(2)O +3H_(2)O` Above 393K, no water of crystallisation is LEFT and anhydrous calcium sulphate, `CaSO_(4)` is formed. This is known as .dead burnt plaster.. `CaSO_(4)(1)/(2)H_(2)O overset(200^(@)C)tounderset("Anhydride")(CaSO_(4)) overset(1100^(@)C)to CaO+SO_(3)`

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