The fixed number of water molecules present in one formula unit of a salt is called water of crystallisation. For instance, there are five molecules of water in one formula unit of copper sulphate and hence the chemical formula for hydrated copper sulphate is \(CuSO_4.5H_2O\).Gypsum has two molecules of water as water of crystallisation and hence the chemical formula for hydrated gypsum stands out to be \(CaSO_4.2H_2O\)This gypsum on getting heated loses water molecules and becomes calcium sulphate hemihydrate (CaSO4. \(\frac12\)H2O). 1. How many molecules of water of crystallization are there in calcium sulphate?(i) 1(ii) 2(iii) 3(iv) 42. Chemical formula for Plaster of Paris is(i)  CaSO4. \(\frac12\)H2O(ii)  CaSO4. 2H2O(iii)  CuSO4. \(\frac12\)H2O(iv)  CuSO4. 2H2O3. Chemical formula for Gypsum is(i) CaSO4. \(\frac12\)H2O(ii) CaSO4. 2H2O(iii)  CuSO4. \(\frac12\)H2O(iv) CuSO4. 2H2O4. Plaster of Paris is prepared by heating gypsum to a temperature of _____ K in a kiln.(i) 273(ii) 373(iii) 100(iv) 5735. True or false. Plaster of paris is not used for making toys, materials for decoration and for making smooth surfaces.(i) TRUE(ii) FALSE