Plaster of Paris

Question 1 Write the chemical formula and name of plaster of paris? 

Question 2 What is gypsum? 

Question 3 Name the calcium compound which hardens on wetting with water? 

Question 4 What will happen if heating is not controlled while preparing plaster of paris? 

Question 5 Name the compound which is used in hospitals for setting fracture bones? 

Question 6 How is plaster of paris prepared from gypsum? 

Question 7 Give few uses of plaster of paris?

Plaster of Paris

Plaster of paris is calcium sulphate hemihydrate.

The chemical formula of Plaster of paris is CaSO₄·½H₂O

It is known as P.O.P.

 

Preparation of Plaster of Paris

It is prepared from gypsum. 

Gypsum is calcium sulphate dihydrate. The chemical formula of gypsum is CaSO₄·2H₂O

Plaster of Paris is prepared by heating gypsum to a temperature of 373K.When gypsum is heated to a temperature of 373k ,It loses three-Fourths of its water of crystallisation and forms Plaster of Paris.

Properties of Plaster of Paris

(1) It is a white powder. 

(2) It has a very remarkable property of setting into a hard mass on wetting with water.

P.O.P. should be stored in a moisture proof container.

Uses of Plaster of Paris

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

(2) It is used in making toys, decorative materials, cheap ornaments, cosmetics, black-board and casts for statues. 

(3) It is used in chemistry laboratories for sealing air gaps in apparatus where air-tight arrangement is required. 

(4) It is used for making surfaces smooth before painting.