Question

1) The change in Freezing Point of a solution is due to presence of solute(s). The more solute is dissolved in the solution, the lower is its freezing point

Select one:

True

False

2) What volume (in L) of a 1.38 M solution of KOH would be needed to prepare 348 mL of a 0.681 M solution?

3) The vapor pressure of a solution is indeed lower that the vapor pressure of the pure solvent. The reason is in part due to surface tension, solvent molecules are more closer to each other because of the presence of solute molecules, leading to increased intermolecular forces and therefore less molecules would escape

Select one:

True

False

Answer 1

1. True. The depression in freezing point of solution increases with increasing concentration of solute in solution.Freezing point is reached when the chemical potential of the pure liquid solvent reaches that of the pure solid solvent. As solute is added into the solvent,the chemical potential of the solution decreases and thus it is expected that the freezing point will change. The chemical potential of the solution or impure solvent requires a colder temperature for it to reach the chemical potential of the solid pure solvent. Therefore, as more of solute is added,lesser is the chemical potential and thus more will be freezing point depression and lower will be the freezing point.

2.3. True

According to Raoult's law, when a nonvolatile solute is dissolved in a solvent, it lowers the vapor pressure of the solvent because of the interactions between solvent and solute molecules.

At this time, there will be solvent to solute attractions which will cause less solvent particles to evaporateare. This happens mainly because there are less solvent molecules at the surface and thus more energy is needed to bring the molecules to surface and make them escape into gas form.