Benzene has a formula of C6H6 and a vapor pressure of 96.4 torr at 298 K. Toluene has a formula of C7H8 and a vapor pressure of 28.9 torr at 298 K. If a solution is made of 299 g of toluene and 391 g of benzene, what is the vapor pressure of the solution?

The vapor pressure of the solution is 55.2 torr

Explanation:

and

where, x = mole fraction in solution

= pressure in the pure state

According to Dalton's law, the total pressure is the sum of individual pressures.

x = mole fraction =

Given : 299 g of toluene and 391 g of benzene.

moles of toluene =

moles of benzene=

Total moles = moles of solute (toluene)  + moles of solvent (benzene) = 3.25 + 5.01 = 8.26

= mole fraction of benzene =

=mole fraction of toluene = (1-0.39) = 0.61

Thus the vapor pressure of the solution is 55.5 torr