Question

Determine the composition of the liquid equilibrium with a vapor containing 70 mol% benzene 30 mol% toluene if the system exists in a vessel under 2 atm pressure. Predict the equilibrium pressure

Answer 1

we know that

Rault's law

Mole fraction of liquid benzene X Pressure of pure benzene = parital pressure of benzene in vapour phase

Dalton's law

Mole fraction of benzene in liquid phase X total pressure of system = Partial pressure in vapour phase

Mole fraction of benzene in liquid phASE

= (total pressure - Pressure of pure toluene) / (Pressure of pure benzene + pressure of pure toluene)

Mole fraction of toluene = Mole fraction of toluene X Pressure of pure benzene / Total pressure

Given :

Total pressure = 2 atmophsere

The composition of liquid = 30% benzene and 70% toluene

The parital pressures will be

Partial pressure of benzene = Mole fraction X total pressure = 0.3 X 2atm = 0.6 atm

Partial pressure of toulene = 0.7 X 2 = 1.4 atm

We need temperature to find the equilibrium pressure