What does Raoult's Law state about vapor pressure?

Raoult's Law describes the relationship between the vapor pressure of a solvent in a solution and its mole fraction. Specifically, it states that the vapor pressure of the solvent in the solution is directly proportional to the vapor pressure of the pure solvent at the same temperature, multiplied by the mole fraction of the solvent in the solution. This means that as the concentration of the solvent decreases due to the presence of solutes, the vapor pressure of the solvent also decreases.

This law is particularly applicable in ideal solutions where interactions between the solvent and solute do not significantly affect the vapor pressures. By knowing the mole fraction, you can predict how the addition of solutes affects the overall vapor pressure of the solution. This understanding is critical in various applications, including distillation and understanding colligative properties of solutions.

The other options do not accurately reflect the principles established by Raoult's Law. For instance, the idea that the vapor pressure of a solution is equal to the sum of pure solvent vapor pressures misunderstands how vapor pressures are calculated in mixtures.