Define water of crystallization mentioning two examples. How can we prove their existence in the examples mentioned in answer?

The water of crystallisation is defined as the water molecules which form part of the structure of a crystal. The salts which contain water of crystallisation are called hydrated salts.

Examples:

1. One formula unit of copper sulphate contains five water molecules (5H₂0). The water molecules which form part of the structure of a crystal are called water of crystallisation.

When heated it loses its blue colour and crystal shape to become a powdery white mass.

$CuSO_{4} .5H_{2} O\ \xrightarrow{heat} CuSO_{4} \ +\ 5H_{2} O$

Blue                              White

2. One formula unit of ferrous sulphate contains seven water molecules (7H₂0). It is also known as Green vitriol as it is green in colour.

When heated it loses its green colour and crystal shape to become a powdery brown mass and gives off the smell of burning sulphur.

$FeSO_{4} .7H_{2} O\xrightarrow{heat} \ FeSO_{4} \ +\ 7H_{2} O$

$2FeSO_{4} \ \xrightarrow{heat} \ \ Fe_{2} O_{3} \ +\ SO_{2} \uparrow +\ SO_{3} \uparrow $