Question

(a) Define ‘water of crystallization’.

(b) Give two examples of substances having water of crystallization. Write their chemical formulae.

Answer 1

Part- (a)

Crystallization: Crystallization is the process of a well-defined arrangement of atoms or molecules in a rigid "space lattice" in order to reduce their energetic state. The smallest unit of "space lattice" is designated a unit, which can accept atoms or molecules to grow a macroscopic crystal.

Part- (b)

The water of crystallization: The water of crystallization means having a fixed number of molecules present in one formula of a unit of salt. Crystal salts with water of crystallization are known as hydrates. The other names for water crystallization are crystallization water or water of hydration.

Following are the two examples of substances having water of crystallization:

1. Copper sulfate pentahydrate with five molecules of water of crystallization. The chemical formula of Copper sulfate pentahydrate is ${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}$.
2. Gypsum with two molecules of water of crystallization. The chemical formula of Gypsum is ${\mathrm{CaSO}}_4.2{\mathrm{H}}_2\mathrm{O}$.

Final answer: hence, the substances having water of crystallization Copper sulfate pentahydrate is ${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}$ and Gypsum is ${\mathrm{CaSO}}_4.2{\mathrm{H}}_2\mathrm{O}$.