What happens to the crystals of washing soda when exposed to air ?

What happens when crystals of washing soda are exposed to air?

Answer the following : What happens when crystals of washing soda are left open in dry air ?

Washing soda is:

Crystals of ferrous sulphate when exposed to air become

When crystals of washing soda are left open in air, they lose

What is the chemical formula of washing soda?

Give reasons : A white powder is formed on the surface of washing soda crystals when left exposed to atmosphere.