Final answer:
Toluene and benzene can have different vapor pressures and still conform to Raoult's law for an ideal solution because vapor pressure depends on intermolecular forces as well as intrinsic molecular properties. In an ideal solution like a benzene-toluene mix, the assumption of similar intermolecular forces simplifies the use of Raoult's law, which states that the total vapor pressure of the solution is the sum of its components' vapor pressures.
Step-by-step explanation:
When applying Raoult's law to ideal solutions, it may seem counterintuitive that two substances like toluene and benzene can have different vapor pressures even though they are said to have equal intermolecular forces. The key here is that even though the intermolecular forces may be similar in magnitude and kind, the actual vapor pressure also depends on the intrinsic properties of the substances such as molar mass and molecular structure.
The concept of an ideal solution assumes that the change in enthalpy upon mixing is zero, indicating that the nature of the intermolecular forces in the mixture is very similar to those in the pure components. In real life, most solutions show some deviation from Raoult's law due to differences in intermolecular interactions.
Therefore, different vapor pressures are attributed not only to intermolecular forces but also to other molecular characteristics, allowing benzene and toluene to have different vapor pressures while still adhering to the concept of an ideal solution where Raoult's law can be applied. The total vapor pressure of the solution is the sum of the partial pressures of its components, each of which is calculated using Raoult's law.