Chemical Engineering - Chemical Engineering Thermodynamics - Discussion

Fugacity in nothing but the pressure of real gas and it is always directly proportional to its mole fraction (Roults law).

Fugacity is a thermodynamic property of a real gas which if substituted for the pressure or partial pressure in the equations for an ideal gas gives equations applicable to the real gas.

This is worked by the Lewis Randall's rule.

Here, the ideal gas in not mentioned in question.

Fugacity is proportional to mole fraction.

We know that the fugacity coefficient of a pure specie present in a binary mixture = fugacity of pure component present in a binary mixture/mole fraction of component in vapor phase*absolute pressure.

Now given that if the temp and pressure is kept const then by hit and trial analogy; fugacity of a pure component present in binary mixture increases when the mole fraction is increased. So answer is B.

Component fugacity is proportional to mole fraction(for ideal solution).