Question

The addition of a solute to a pure solvent ______ its vapour pressure but ______ its boiling point.

Answer 1

The addition of a solute to a pure solvent lowers its vapour pressure but increases its boiling point.

Explanation:

Adding a non-volatile solute decreases the number of solvent molecules on the surface, resulting in a lower vapour pressure. Since boiling occurs when vapour pressure equals external pressure, the solution must be heated to a higher temperature to boil; the boiling point increases.