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Question
Plaster of Paris is prepared by heating one of the following to a temperature of 100°C. This is:
Options
CaSO3.2H2O
CaCl2.2H2O
CaCO3.2H2O
CaSO4.2H2O
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Solution
CaSO4.2H2O
Explanation:
Plaster of Paris (POP) is prepared by carefully heating gypsum, which is chemically known as calcium sulphate dihydrate (CaSO4.2H2O), to exactly 100°C (373 K). At this temperature, gypsum loses three-fourths of its water of crystallisation, forming calcium sulphate hemihydrate, which is POP. If heated above 100°C, it loses all its water, becoming “dead burnt plaster” (anhydrous calcium sulphate) and losing its setting properties.
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Match the Following:
| 1. | Antiseptic | a. | Plaster of paris |
| 2. | Making casts for statues | b. | Phenol |
| 3. | Ease stress and relaxes | c. | Gypsum |
| 4. | Fertilizers | d. | Epsum |
Analogy:
______: Calcium Sulphate Dihydrate:: Plaster of Paris: Calcium Sulphate Hemihvdrate.
