Van't hoff factor, solvent and solute

Question

1. I add a non-volatile solute to a pure solvent to form a solution. Will the vapor pressure of this newly formed solution be lower than that of the pure solvent at the PURE SOLVENT's normal boiling point? 

2. Is it true that the actual Van't hoff's factor tend to deviate greatly from the theoretical Van't hoff's factor under these two conditions

--- high solute concentration

- greater magnitude of charge

Answer 1

Boiling point is a colligative property meaning it depends on the number of particles and not the nature of the particles. Also, boiling point is the temperature at which the vapor pressure equals the atmospheric pressure. Vapor pressure of a pure solvent will decrease when a non volatile solute is added. Putting these facts together, it is clear that the boiling point of the solution will be higher than that of the pure solvent.

It is true that the actual vant Hoff factor deviates from theoretical value under the conditions described. The actual values will be LOWER than theoretical.