Question

A compound' a'on heating at 370k gives b used as plaster for supporting fractured bones in the right position b on mixing with water changes to a identify a and b and write the chemical reaction

Answer 1

a= Gypsum (CaSO4.2H2O) also called calcium sulphate di hydrate

b= Plaster of Paris (CaSO4.1/2H2O) also called calcium sulphate hemi hydrate.

Chemical reactions taking place are:

(1) CaSO4.2H2O(Gypsum)(heat)----->

CaSO4.1/2H2O(POP)+3/2H2O(water vapours)

(2) CaSO4.1/2H2O(POP)+3/2H20(water)

--------> CaSO4.2H2O(Gypsum) + heat