Example 05.03 Activity Coefficients from Experimental xyPT-Data
Calculate the activity coefficients for the system ethanol (1) - water (2) at theta = 70 °C from experimental VLE data at a given composition.
Liquid and vapor mole fractions, temperature, pressure
Vapor pressure of the pure components
Virial coefficients at theta = 70°C
Solution a) neglecting the real vapor phase behavior and the Poynting correction
Solution b) taking into account the real vapor phase behavior using the Virial
equation and using the Poynting correction
The second virial coefficient of the mixture is calculated by:
Calculation of the fugacity coefficients of the components in the mixture:
Calculation of the fugacity coefficients of the pure components in the saturated state:
Calculation of the Poynting factor:
Calculation of the activity coefficients
In this low pressure case, the real vapor phase behavior and the Poynting correction are not very important. Things become different if higher pressures are involved.