Question

Assertion : The vapour pressure of a liquid decreases if some non-volatile solute is dissolved in it.
Reason : The relative lowering of vapour pressure of a solution containing a non-volatile solute is equal to the mole fraction of the solute in the solution.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (B)

On adding a non volatile solute in a liquid the vapour pressure decreases because some molecules of the solvent on the surface are replaced by the molecules of the solute.