08.03 - The Entropy Departure Function


The Entropy Departure Function  (11:22) (uakron.edu)
Deriving the general formula for the entropy departure function is analogous to the derivation for the internal energy formula. There are two points of interest however: (1) The entropy formula for an ideal gas depends on volume (or pressure) as well as temperature, necessitating a contribution of lnZ to correct from Sig(T,V) to Sig(T,P). (2) When all is said and done, combining S with U (derived in 08.02) gives A (=U-TS) and A gives G (=A+PV), implying that other departure functions can be obtained by simple arithmetic applied to U and S.

Comprehension Questions: The RK EOS can be written as: Z = 1/(1-) - /(RT1.5).
1.  Use Eqn. 8.19 to solve for (S-Sig)TV/R of the RK EOS.
2.  Use Eqn. 8.27 to solve for (A-Aig)TV/RT of the RK EOS.
3.  Use Eqns. 8.22 and 8.27 to solve for (S-Sig)TV/R of the RK EOS.

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