Question

Consider a solution made from a nonvolatile solute and a volatile solvent. Which statement is true?

a) The vapor pressure of the solution is always greater than the vapor pressure of the pure solvent.

b) The boiling point of the solution is always greater than the boiling point of the pure solvent.

c) The freezing point of the solution is always greater than the freezing point of the pure solvent.

Answer 1

b) The boiling point of the solution is always greater than the boiling point of the pure solvent.

Because

When anon volatile solute is added to avolatile solvent, the vapor pressure of the solution (above the resulting solutiion) is less than the vapor pressure of the pure solvent. The boiling point of a solution, then, will be greater than the boiling point of the pure solvent because the solution (which has a lower vapor pressure) will need to be heated to a higher temperature in order for the vapor pressure to become equal to the external pressure (i.e., the boiling point)