Details

The saturation pressure of component is calculated using the Antoine equation:

,

where , , and are Antoine constants, is temperature (°C), and is in bar.

The two-parameter Margules model is used to calculate the activity coefficients for a non-ideal liquid mixture of benzene and ethanol . This model fits the excess Gibbs free energy:

,

where is excess Gibbs energy, and is the ideal gas constant.

The activity coefficients , are given by:

,

,

where and are the liquid mole fractions of benzene and ethanol and , and and are the Margules parameters.

The modified Raoult's law is used to calculate the bubble-point and dew-point pressures using the factors:

,

where is the vapor mole fraction and , and is the total pressure (bar).

Bubble-point pressure calculation:

.

Dew-point pressure calculation:

.

The screencast video at [2] shows how to use this Demonstration.

References

[1] J. R. Elliott and C. T. Lira, Introductory Chemical Engineering Thermodynamics, New York: Prentice Hall, 2012 pp. 372–377, 430.

[2] Vapor-Liquid Equilibrium Diagram for Non-Ideal Mixture. www.colorado.edu/learncheme/thermodynamics/VLEDiagramNonIdealMixture.html.