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What is dead burnt plaster ? Why is it so called ? |
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Answer» Solution :When gypsum or PLASTER of Paris is heated above 393 K , it loses all the water of CRYSTALLIZATION and anhydrous calcium sulphate is obtained . `Caunderset("Gypsum")(SO_(4).2H_(2)) O overset( gt 393K)(to) underset("Dead burnt plaster")(CaSO_(4)) + 2H_(2)O` `2 underset("Plaster of Paris")(CaSO_(4).2H_(2)) O overset(gt 393 K)(to) 2 CaSO_(4) + H_(2)O` Anhydrous calcium sulphate does not absorb water to form gypsum and HENCE loses the properties of setting with water . That is why anhydrous calcium sulphate is called dead burnt plaster . |
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