Question

Substances exposed to atmosphere at ordinary temperature , lose their water of crystallization
are called as

Answer 1

Answer:

Deliquescene

lt is the process by which a substance absorbs moisture from the atmosphere until it absorbs water and forms a solution.

Answer 2

Substances which lose their water of crystallization on being exposed to atmosphere are called efflorescent substances.

• Efflorescence is the property of hydrated salts, containing water of crystallization, to lose their water molecules by evaporation, when left open in the air.

• Now let us understand, what causes efflorescence. When the vapour pressure of the water molecules in a salt is greater than the vapour pressure of the atmosphere, the water molecules from the salt escape into the atmosphere to balance the pressure outside.

• Efflorescence converts a crystalline salt into a powdery substance, as the water molecules that impart crystalline structure to the salt are lost.

• The turning of washing soda crystals (Na₂CO₃.10H₂O) into a white powdery substance on being exposed to atmosphere is a very common example of efflorescence.