This simulation shows how the fugacities of benzene (B) and toluene (T) change with pressure and composition at constant temperature. The liquid mixture is modeled as an ideal solution and the gas phase is ideal, so Raoult's law is used for vapor-liquid equilibrium. Use sliders to vary the temperature and overall mole fraction of benzene. Use buttons to view the pressure-composition diagram (P-x-y), the fugacity-pressure plot or both plots at once. Black dots on the diagrams represent the phase behavior for the selected pressure and composition.

The saturation pressures P_i^sat were calculated using the Antoine equation:

P_i^sat = 10^{(A_i - B_i / (T + C_i))}

where i represents either benzene or toluene (B or T), T is temperature (°C), and A_i, B_i and C_i are Antoine constants.

The fugacity f_i of a component depends on temperature and molar composition.

In the liquid region:

f_i = x_i P_i^sat,

where x_i is the liquid mole fraction and both P_i^sat and f_i have units of bar.

In the vapor region:

f_i = y_i P,

where y_i is the vapor molar composition and P is the total pressure (bar).

When vapor and liquid are in equilibrium (VLE):

f_i = y_i P = x_i P_i^sat.

This simulation was created in the Department of Chemical and Biological Engineering at University of Colorado Boulder for LearnChemE.com by Sanjay Baskaran under the direction of Professor John L. Falconer and Michelle Medlin. It is a JavaScript/HTML5 implementation of a Mathematica simulation by Neil Hendren. It was prepared with financial support from the National Science Foundation (DUE 2336987 and 2336988) in collaboration with Washington State University. Address any questions or comments to LearnChemE@gmail.com.