Long Answer Type
Short Answer TypeHow is quick lime prepared on a commercial scale? How is it converted into slaked lime?
Long Answer TypeWhat is Plaster of Paris? How is it prepared? What are its properties and uses?
Plaster of Paris is calcium sulphate hemihydrate.
Preparation:
(i) From gypsum (CaSO4. 2H2O): When gypsum is heated to about 393 - 403 K, partial dehydration takes place with the formation of Plaster of Paris. 
(ii) On a large scale, gypsum is gradually heated in a large steel vessel, holding several tonnes of material. This steel vessel is provided with a mechanical stirrer. During heating, the gypsum is stirred mechanically and the temperature is maintained between 393 - 403 K.
The temperature should be controlled carefully between 393 - 403 K, otherwise above this temperature (say 473 K), the whole of the water of hydration is lost and the gypsum gets dead burnt.
Properties:
(i) It is a white powder.
(ii) When mixed with water, Plaster of Paris quickly solidifies to gypsum with the evolution of heat and also expands slightly.
(iii) The action of heat: When plaster of Paris is heated at 473 K, it forms anhydrous calcium sulphate.
Uses. (i) It is used in surgery for plastering fractured parts of the body.
(ii) It is used for making casts for statues and for preparing blackboard chalks.
What is the effect of heat on the following compounds? (Write equations for the reactions):
(i) Calcium Carbonate
(ii) Magnesium chloride hexahydrate
(iii) Gypsum
(iv) Magnesium sulphate heptahydrate
Short Answer Type
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