Details

Enthalpy and entropy are calculated using the Peng–Robinson equation of state (EOS) for a real gas and the ideal gas law for an ideal gas:

,

,

where is in kJ/mol and is in kJ/[mol K]; the superscript represents an ideal gas, the subscript refers to the reference state, and and are the enthalpy and entropy departure functions for a real gas calculated from the Peng–Robinson EOS, while and are the ideal gas enthalpy and entropy at the reference state.

,

,

where , , , and are heat capacity constants (), is temperature (K), and is pressure (MPa).

,

,

,

,

,

where is the compressibility factor, is the reduced temperature (dimensionless, not to be confused with ), is the critical temperature (K), is the acentric factor, and and are constants.

,

,

,

where and are constants, is the reduced pressure (dimensionless, not to be confused with ), and is the critical pressure (MPa).

These equations are used to calculate the compressibility factor :

,

,

,

,

where , , , , , and are constants used for simplification.

,

,

.

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

Reference

[1] Enthalpy and Entropy Departure Functions for Gases. www.colorado.edu/learncheme/thermodynamics/EntropyEnthalpyDepartureFunctions.html.