Question

Give suitable chemical term for

The process in which a substance absorbs moisture from the atmospheric air to become moist and ultimately dissolves in the absorbed water.

Answer 1

Deliquescence

• The absorption of atmospheric water vapour by a crystalline solid until the crystal eventually dissolves into a saturated solution.
• This phenomenon is called deliquescence.
• Thermodynamically deliquescence occurs when the partial pressure of the water vapour in the air exceeds the vapour pressure of water in the saturated solution of the salt.
• Substances which are highly soluble in water have a greater tendency to be deliquescent as concentrated solution have a lower vapour pressure.

Example:

Sodium chloride (NaCl) turns moist and ultimately forms a solution on exposure to air.

NaCl (s) + H₂O(g) ⇢ NaCl (aq)