Question

Equal moles of benzene and toluene and makes the vapour pressure of benzene and toluene in pure state are 700 and 600 mmhg respectively the mole fraction of benzene in vapour state is

Answer 1

Let us consider the number of moles of benzene and toluene be

$x$

Thus their mole fractions will be =

$\frac{Numberofmolesofsolute}{Numberofmolesofsolute+solvent}$

$Molefraction=\frac{x}{2x}=\frac{1}{2}$

$Vaporpressureofbenzeneinpurestateis=700mmHg$

$Vaporpressureoftolueneinpurestate=600mmHg$

$Totalvaporpressure=Vaporpressureinpurestate\times molefractionofeach$

$Totalvaporpressure=700\times \frac{1}{2}+600\times \frac{1}{2}$

$Totalvaporpressure=650mmofHg$

$Molefractionof{C}_6{H}_{6}invaporstate=Vaporpressureofbenzeneinpurestate\times \frac{1}{2}+Totalvaporpressure\times Y$

$Molefractionof{C}_6{H}_{6}invaporstate=700\times \frac{1}{2}+650\times Y$

$Y=\frac{350}{650}=0.54$