Q61 / 180 · AIIMS 2018 (27 May) · Chemistry

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 nonvolatile 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.
  • Correct answer
    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.

Solution

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.

Hence, the correct answer is option: 'B'.

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