Question

A system of water (1) and methane (2) exists as two phases at 298 K and 23.23 atm. Rigby and Prausnitz (1968) reported the water mole fraction in the vapor phase as 1.483 × 10−3. The vapor phase is represented by the virial equation of state with the following parameters:

B11 = −1165 cm3/mol, B22 = −43.4 cm3/mol.

(a) Estimate the liquid phase composition.

(b) Determine the second virial cross coefficient, B12. The vapor pressure of

water at 298 K is 0.03126 atm.

Answer 1

The ideal gas equation for ideal gases are given as :

P is the pressure and is the molar volume of gas and T is the temperature and R is the universal gas constant.

Virial equation of state is given by :

The coefficients B,C are second, third virial coefficients which are functions of temperature.

The above equation is given in simplified form for gases upto a few atmospheric pressure when temperature is not very low

;   is the ideal molar volume

So from the above equation it can be concluded that B(T) is the correction to ideal molar volume.

From vapour liquid data find the vapour pressure

x=0.000562