Answer:
Mole fraction for benzene is 0.683
Explanation:
We need to determine the colligative property about vapour pressure which formula is:
ΔP = P° . Xm
where P° is vapour pressure of pure solvent.
ΔP = Vapor pressure of pure solvent - Vapor pressure of solution
In this case, our solvent is benzene and the solute is toluene. For this colligative property vapour pressure of solution is lower than pure solvent.
P° of benzene at 20°C is 74.7 Torr
Xm is the value for the mole fraction of solute.
Let's replace data: 74.7 Torr - 51 Torr = 74.7 Torr . Xm
Xm = 0.317 → That's the mole fraction for toluene.
Then, mole fraction for benzene will be: 1 - 0.317 → 0.683
