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

`P_("Benzene") = X_("Benzene") P_"Benzene"^@ P_("Toluene") = X_("Toluene") P_"Toluene"^@`
For an ideal 1 : 1 molar mixture of benzene and toluene,
`x_("Benzene") =1/2 and x_("Toluene") =1/2`
`P_("benzene") = 1/2 P_"Benzene"^@ = 1/2 xx12.8kPa = 6.4 kPa`
`P_("Toluene") = 1/2 P_"Toluene"^@=1/2 xx 3.85 kPa = 1.925 kPa`
Thus, the vapour will contain a high percentage of benzene as the partial vapour pressure of benzene is higher as compared to that of toluene.