In a non-ideal solution, what does a positive deviation from Raoult's Law indicate?

In a non-ideal solution, a positive deviation from Raoult's Law indicates that the intermolecular forces between the components of the solution are weaker than expected. Raoult's Law suggests that the vapor pressure of a solution is proportional to the mole fraction of each component in the solution, assuming that the components interact ideally.

When a solution demonstrates a positive deviation, it means that the actual vapor pressure of the solution is higher than what would be predicted by Raoult’s Law. This higher vapor pressure occurs because the interactions between the different molecules in the solution are weaker than the interactions that would occur if each component behaved ideally. As a result, the molecules can escape into the vapor phase more easily, leading to an increase in vapor pressure.

In an ideal solution, the attraction between unlike molecules is similar to that between like molecules; in a non-ideal scenario with positive deviation, the difference in strength means that the system behaves differently, allowing for a greater proportion of the solute molecules to enter the vapor phase compared to what Raoult's Law would suggest. This reinforces the idea that the intermolecular forces are indeed weaker in this case.