A P Ch emistry 9 Which of the following statements is true f

A P Ch emistry 9. Which of the following statements is true for all aqueous solutions? I. Vapor pressure is lower than that of pure water. II. Boiling point is higher than that of pure water 111. Freezing point is lower than that of pure water (A) I only (B) I and II only (C) II only (D) III only (E) I, II, and III

Solution

The correct answer is E i.e. all statements are correct.

Vapor pressure is exerted when liquid molecules escape the surface to go into vapor phase. In aqueous solution, non-volatile solutes are present at the surface which decreases the tendency to escape and thereby decreasing vapor pressure as compared to pure water.

Also, when vapor pressure is less high temperature is required to boil the liquid. So, the boiling point is higher than that of pure water.

Freezing point is less than that of pure water as interactions between liquid particles is less as in case of pure water.