# 08.02 - The Internal Energy Departure Function

## Comments

### The Internal Energy Departure

The Internal Energy Departure Function (11min, uakron.edu) Deriving departure functions for a variety of equations of state is simplified by transforming to dimensionless units and using density instead of volume. This also leads to an extra simplification for the internal energy departure function.

Comprehension Questions:

1. What is the value of T(∂P/∂T)V - P for an ideal gas?
2. What is the value of (∂U/∂V)T for an ideal gas and how can you explain this result at the molecular scale?
3. The Redlich-Kwong (RK) EOS is: P=RT/(V-b) -a/(V2RT1.5). Use Eqn. 8.13 to solve for (U-Uig)/RT of the RK EOS.
4. The RK EOS can be written as: Z = 1/(1-) - /(RT1.5). Use Eqn. 8.14 to solve for (U-Uig)/RT of the RK EOS.

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### Departure Function Derivation: Sections 8.2 - 8.8

Departure Function Derivation Principles (8:03) (msu.edu)
This screencast covers sections 8.2 - 8.8. Concepts of using the equation of state to evaluate departure functions. The screencasts also discusses the choice of density integrals or pressure integrals. The use of a reference state is discussed.

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