Question

How is plaster of Paris chemically different from gypsum? How may these be inter converted? Write one use of plaster of Paris?

Answer 1

Plaster of Paris is different from Gypsum in term of water of crystallization.Gypsom has 2 mole of water of crystallization where as Plaster of Paris has half mole of water of crystallization.Plaster of Paris is prepared from heating gypsum.

CaSO₄.2H₂O ------Heat/273 k--> CaSO₄.1/2 H₂O

When plaster of Paris is mixed with water it get converted into Gypsum

CaSO₄.1/2 H₂O + 3/2 H₂O ----------> CaSO₄.2H₂O

The use of plaster of Paris are- 

(i) It is used for making moulds or casts for toys pottery, ceramics etc. 

(ii) In surgical bandages for setting fractured bones.