Question

Discuss why the freesing point of a solution is typically lower than the freezing poiunt of pure solvent

Answer 1

Whenever a non volatile solute is added to a volatile solvent , the vapour pressure of the solution decreases. This lowering of vapour pressure of the solution causes the lowering of the freezing point of the solution .

Since you may know that freezing point of the substance is the temperature at which vapour pressure of the substance in its liquid phase becomes equal to the vapour pressure in its solid phase . Now when the non volatile solute has been added to the solvent , the temperature at which both the vapour pressures become equal occur at a lower temperature than that of the pure solvent freezing point.

Hence the freezing point of the solution decreases.