How do you prepare bleaching powder and plaster of Paris?
Anonymous:
bleaching powder by passing chlorine through liime water
and plaster of Paris by heating gypsum at 100°C
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Plaster of Paris is prepared by heating gypsum (CaSO4.2H2O) to a temperature of 373 K in a kiln. Actually the chemical name of gypsum is calcium sulphate dihydrate which means that the molecule of gypsum is in fact molecule of calcium sulphate which contains two molecules of water of crystallization. So when gypsum is heated then it loses one and half molecules of water of crystallization leaving only half molecule of water of crystallization remaining attached with calcium sulphate.
During this process care should be taken not to heat the gypsum above 373K because if gypsum is heated beyond the temperature 373 K then all the water of crystallization is removed from it which results in anhydrous calcium sulphate which is also called as dead burnt plaster. The disadvantage of this dead burnt plaster is that it doesn’t set like plaster of Paris after adding in water.
During this process care should be taken not to heat the gypsum above 373K because if gypsum is heated beyond the temperature 373 K then all the water of crystallization is removed from it which results in anhydrous calcium sulphate which is also called as dead burnt plaster. The disadvantage of this dead burnt plaster is that it doesn’t set like plaster of Paris after adding in water.
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bleaching powder is prepared from calcium hydroxide by the action of chlorine
Ca(OH)2+cl2=caocl2+H2O
plaster of Paris
CaSO4.1/2H2O+1 1/2H2O=CaSO4.2H2O.
Ca(OH)2+cl2=caocl2+H2O
plaster of Paris
CaSO4.1/2H2O+1 1/2H2O=CaSO4.2H2O.
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