Question

The number of water molecules in one molecule of gypsum, dead burnt plaster and plaster of paris, respectively

Answer 1

The chemical formulae of the given compounds are:

(i) Gypsum	$CaS{O}_4.2H_{2}O$
(ii) Dead burnt plaster	$CaS{O}_4$
(iii) Plaster of Paris	$CaS{O}_4.\frac{1}{2}{H}_{2}O$

$\therefore$ The number of water molecules in gypsum, dead burnt plaster and plaster of Paris are respectively, $2,0$ and $0.5$.