Which of the following statements about the composition of the vapour over an ideal 1 : 1 molar mixture of…

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 25oC . (Given vapour pressure data at 25oC , benzene = 12.8 kPa, toluene = 3.85 kPa)
  1. The vapour will contain a higher percentage of benzene.
  2. The vapour will contain a higher percentage of toluene.
  3. The vapour will contain equal amounts of benzene and toluene.
  4. Not enough information is given to make a prediction.

Solution

A - benzene, B - Toluene
PT=PAo XA+PBo XB
=12.8×0.5+3.85×0.5
=6.2+1.925
=8.125
Also, mole fraction of benzene in vapour form
YA=PAo XAPT=6.28.121=0.75
And mole fraction of Toluene in vapour form
YB=1-0.75=0.25

Asked in: NEET 2016 (Phase 1)

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