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

Answer

C

Explanation

Mole fraction of benzene `(x_(b)) = (1)/(2)`
Mole fraction of toluene `(x_(l)) =(1)/(2)`
Vapour pressure of benzene `(p_(b)) = 12.8 xx (1)/(2) = 6.4 kPa`
Vapour pressure of toluene `(p_(t)) = 3.85 xx (1)/(2) = 1.925 kPa`
Total vapour pressure of solution `(p) = 6.4 +1.925`
` = 8.325 kPa`
Mole fraction of benzene in vapour phase ` = (6.4)/(8.325) = 0.77`
Mole fraction of toluene in vapour phase `= (1.925)/(8.325) = 0.23`
The vapour will contain higher percentage of benzene.