Which of the following statements about the composition of the vapour over an ideal `1:1` mol mixture of benzene and toluene is correct? Assume that the temperature is constant at `25^(@)C`. (Given: vapour pressure Date at `25^(@)C`, benzene=12.8 kP, toluene=3.85 kPa)

Options

A. The vapour will contain a higher percentage of benzene
B. The vapour will contain a higher percentage of toluene
C. The vapour will contain equal amounts of benzene and toluene
D. Not enough information is given to make a predication

Answer

A

Explanation

`Ararr` benzene, `Brarr` toluene
1 : 1 molar mixture of A and B
`therefore x_(A)=(1)/(2) and x_(B)=(1)/(2)`
`P_(s)=P_(A)^(0)X_(A)+P_(B)^(0)X_(B)`
`P_(s)=12.8xx(1)/(2)+3.85xx(1)/(2)=8.325kPa`
`Y_(A)=(P_(A)^(0)X_(A))/(P_(s))=(12.8xx(1)/(2))/(8.325)=0.768`
`therefore Y_(B)=1-Y_(A)=1-0.768=0.232`
So, the vapour will contain higher percentage of benzene.