Problem 11-63

b. The composition in mole fraction of pentane in the vapor phase can be calculated from the pressure

For a gas:
                P_total = P_a + P_b

                n_total = n_a + n_b       (PV = nRT)

In this problem (all vapor phase):

χ pentane= nPentane ntotal	is the same as	χ pentane= PPentane Ptotal