What effect does the presence of a nonvolatile solute have upon the boiling point of a solution

Yes, nonvolatile solute lowers the vapor pressure and increases the boiling point. For instance, salt is an example of an nonvolatile solute in water. Ever wonder why salt is used in icy roadways in the winter? Because salt help inhibit the crystallization of water particles into ice by lowering the freezing point.

Problem 17Q

How does the presence of a nonvolatile solute affect the boiling point and melting point of a solution relative to the boiling point and melting point of the pure solvent?

Step-by-Step Solution:

Step 1 of 3

Solution: Here, we are going to explain how the pressure of a nonvolatile solute affect the boiling and melting point of a solution relative to the boiling and melting point of the pure solvent.

Step1:

In a pure liquid the entire surface is occupied by the molecules of the liquid. If a non-volatile solute is added to a solvent to give a solution, the vapour pressure of the solution is solely from the solvent alone. This vapour pressure of the solution at a given temperature is found to be lower than the vapour pressure of the pure solvent at the same temperature. In the solution, the surface has both solute and solvent molecules; thereby the fraction of the surface covered by the solvent molecules gets reduced. Consequently, the number of solvent molecules escaping from the surface is correspondingly reduced, thus, the vapour pressure is also reduced.

A liquid boils at the temperature at which its vapour pressure is equal to the atmospheric pressure. Now, in order to make the solution boil, its vapour pressure must be increased by raising the temperature above the boiling temperature of the pure solvent. Thus, the boiling point of a solution is always higher than that of the boiling point of the pure solvent in which the solution is prepared .

Step2:

Again, at the melting point of a substance, the solid phase is in dynamic equilibrium with the liquid phase. Thus, the melting point of a substance may be defined as the temperature at which the vapour pressure of the substance in its liquid phase is equal to its vapour pressure in the solid phase.

When a non-volatile solid is added to the solvent its vapour pressure decreases and now it would become equal to that of solid solvent at lower temperature. Thus, the melting point of the solvent decreases.

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Introductory Chemistry was written by and is associated to the ISBN: 9780321910295. The full step-by-step solution to problem: 17Q from chapter: 13 was answered by , our top Chemistry solution expert on 05/06/17, 06:45PM. Since the solution to 17Q from 13 chapter was answered, more than 1241 students have viewed the full step-by-step answer. This textbook survival guide was created for the textbook: Introductory Chemistry, edition: 5. The answer to “?How does the presence of a nonvolatile solute affect the boiling point and melting point of a solution relative to the boiling point and melting point of the pure solvent?” is broken down into a number of easy to follow steps, and 30 words. This full solution covers the following key subjects: point, boiling, Melting, presence, affect. This expansive textbook survival guide covers 19 chapters, and 2046 solutions.

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