Question

Boiling point of benzene and toluene solution is 130 celsius.calculate ratio of pbenzene/ptoluene at 130 Celsius. Mole fraction of benzene in solution is 0.4

Answer 1

Benzene and toluene form an ideal solution over the entire range of composition. The vapour pressure of pure benzene and toluene at 300 K are 50.71 mm Hg and 32.06 mm Hg respectively. Calculate the mole fraction of benzene in vapour phase if 80 g of benzene is mixed with 100 g of toluene.

Explanation:

Number of moles is the ratio of mass to molar mass.

The molar masses of benzene and toluene are 78 g/mol and 92 g/mol respectively.

Number of moles of benzene =7880=1.026

Number of moles of toluene =92100=1.087

Mole fraction of benzene, XB=1.026+1.0871.026=0.486

Mole fraction of toluene, XT=1−0.486=0.514

PB=PBo×XB=50.71×0.486=24.65 mm Hg

PT=PToXT=32.06×0.514=16.48 mm of Hg

Total vapour pressure =24.65+16.48=41.13 mm Hg

Mole fraction of benzene in vapour phase is as follows:

YB=41.1324.65=0.60