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

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 Garrison J. Vigil and Rachael L. Baumann. 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.