Here are the calculations for the vapor pressure contribution of methylbenzene.
Assumption: The vapor pressure of pure methylbenzene (Pmethylbenzene∘) is not provided. Therefore, the vapor pressure contributions of methylbenzene will be expressed in terms of Pmethylbenzene∘.
Step 1: Use the mole fractions of methylbenzene (Xmethylbenzene) calculated previously.
Step 2: Calculate the vapor pressure contribution of methylbenzene (Pmethylbenzene).
According to Raoult's Law for an ideal solution:
Pmethylbenzene=XmethylbenzenePmethylbenzene∘
where Pmethylbenzene∘ is the vapor pressure of pure methylbenzene.
Here are the results for the given concentrations:
| Xbenzene | Xmethylbenzene | Pmethylbenzene (Vapor Pressure Contribution) |
| :------------------- | :------------------------- | :------------------------------------------------------- |
| 0 | 1 | 1⋅Pmethylbenzene∘=Pmethylbenzene∘ |
| 0.25 | 0.75 | 0.75⋅Pmethylbenzene∘ |
| 0.5 | 0.5 | 0.5⋅Pmethylbenzene∘ |
| 0.75 | 0.25 | 0.25⋅Pmethylbenzene∘ |
| 1 | 0 | 0⋅Pmethylbenzene∘=0 |
The respective vapor pressure contributions of methylbenzene are Pmethylbenzene∘, 0.75Pmethylbenzene∘, 0.5Pmethylbenzene∘, 0.25Pmethylbenzene∘, 0.