Question

What is the water of crystallisation of plaster of paris and gypsum. why is it so?

Answer 1

water of crystallization is the fixed no. of water molecules present in one formula unit of a salt in its crystaline form.plaster of paris is obtained from on careful heating of gypsum. on careful heating of gypsum at 373k , it loses water molecules partially to become calcium sulphate hemihydrate. this is called plaster of paris (CaSO4.1/2 H2O). plaster of paris is a white powder and on mixing with water, it sets into hard solid mass due t the formation of gypsum.                                  CaSO4. 1/2 H2O+1 1/2 H2O = CaSO4. 2H2O.

Answer 2

Answer:

Water of crystallisation is the fixed number of water molecules present

in one formula unit of a salt.

Explanation:

Five water molecules are present in one

formula unit of copper sulphate. Chemical formula for hydrated copper

sulphate is Cu SO4. 5H2O. Now you would be able to answer the question

whether the molecule of Na2CO3.10H2O is wet.

One other salt, which possesses water of crystallisation is gypsum.

It has two water molecules as water of cyrstallisation. It has the chemical

formula CaSO4.2H2