question_answer 106)

  Assertion (A) When NaCI is added to water a depression in freezing point is observed. Reason (R) The lowering of vapour pressure of a solution causes depression in the freezing point.

Answer:

                  (a) Assertion and reason both are correct and reason is correct explanation of assertion. When NaCI is added to water a depression in freezing point is observed. This is due to lowering of vapour pressure of a solution. Lowering of vapour pressure is observed due to intermolecular interaction of solvent-solute particles.