Details

This system is assumed to obey Raoult's law. The saturation pressures (bar) of -hexane () and -octane () are calculated from the Antoine equation, where the Antoine coefficients , , and are constants and (°C) is temperature:

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In order for the components to be in vapor-liquid equilibrium (VLE), the total pressure must equal the sum of the partial pressures:

.

Here, and are the liquid mole fractions of -hexane and -octane. The mole fractions of -hexane and -octane in the vapor phase are and . Initially the system contains -hexane and -octane in VLE. When -hexane (the component with the higher vapor pressure) is added at constant temperature, vaporization returns the mixture to VLE. By contrast, if -octane (lower vapor pressure) is added at constant temperature, condensation returns the mixture to VLE.

The screencast video at [1] explains how to use this Demonstration.

Reference

[1] Adding One Component to a Binary VLE Mixture [Video]. (Dec 16, 2020) www.learncheme.com/simulations/thermodynamics/thermo-2/adding-one-component-to-a-binary-vle-mixture.