Question

On adding the proper amount of water to plaster of paris, hard and porous solid compound is obtained. Identify this compound and show its method of preparation by chemical equation. Give one use of plaster of paris in hospital.​

Answer 1

(a) Plaster of Paris is calcium sulphate hemihydrate. Its chemical formula is: CaSO

4

.

2

1

H

2

O.

(b) It is prepared by heating gypsum to a temperature of 100

0

C in a kiln. It loses 3/4th of its water of crystallisation and forms plaster of Paris.

Gypsum

CaSO

4

.2H

2

O

Heat at 100

0

C

373k

Plaster of paris

CaSO

4

.

2

1

H

2

O

+

water

1

2

1

H

2

O

(c) Plaster of Paris should be stored in a moisture-proof container because the presence of moisture can cause the slow setting of the plaster of Paris by bringing about its hydration.

(d) Uses of plaster of Paris:

(i) It is used as a fire proofing material.

(ii) it is used in hospitals for setting fractured bones in the right position to ensure correct healing.