Question

A solution of methanol and water has a mole fraction of water of 0.312 and a total vapor pressure of 21 torr at 39.9 degrees C. The vapor pressures of pure methanol and pure water at this temperature are 256 torr and 55.3 torr , respectively.

Is the solution Ideal? NO, it isnt.

What can you say about the relative strengths of the solute-solvent interactions compared to the solute-solute and solvent-solvent interactions?

a. the methanol-water interactions are stronger than the methanol-methanol and water-water interactions.
b. the methanol-water interactions are weaker than the methanol-methanol and water-water interactions.

Answer 1

Based on the conditions given as vapor pressure is 256 torr,the methanol-water interactions are stronger than the methanol-methanol and water-water interactions is the correct option.

Answer 2

Step-by-step explanation:

Given the details, we can say that

Pure methanol is a volatile solvent as the vapour pressure has a high value. This means that methanol - methanol intermolecular forces are weak in comparisson to water - water forces. When having about 30% of water in a methanol mixture, the mixture Pv decreased, showing that it is not a volatile mixture, so then there are strong intermolecular interactions between methanol - water, part of it due to the hydrogen bonds.