1. Now we are going to start looking at models for the chemical potential mi of a given component i in a mixture
The first model is the ideal gas mixture
The second model is the ideal solution
As you study this, think about the differences, not only mathematical but also the physical differences of these models

2. The ideal-gas mixture model
EOS for an ideal gas
Calculate the partial molar volume for an ideal gas component of an ideal gas mixture

3. For an ideal gas mixture

4. For any partial molar property other than volume, in an ideal gas mixture:

5. Partial molar entropy (igm)

6. Partial molar Gibbs energy
Chemical potential of component i in an ideal gas mixture
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7. This is m for a pure component !!!

8. Problem
What is the change in entropy when 0.7 m3 of CO2 and 0.3 m3 of N2, each at 1 bar and 25oC blend to form a gas mixture at the same conditions? Assume ideal gases.
We showed that:

9. solution
n = PV/RT= 1 bar 1 m3/ [R x 278 K]
DS = J/K

10. Problem
What is the ideal work for the separation of an equimolar mixture of methane and ethane at 175oC and 3 bar in a steady-flow process into product streams of the pure gases at 35oC and 1 bar if the surroundings temperature Ts = 300K?
Read section 5.8 (calculation of ideal work)
Think about the process: separation of gases and change of state
First calculate DH and DS for methane and for ethane changing their state from
P1, T1, to P2T2
Second, calculate DH for de-mixing and DS for de-mixing from a mixture of ideal
gases

11. solution Wideal = DH – Ts DS = -2484 J/mol = -7228 J/mol
= J/mol K
Wideal = DH – Ts DS = J/mol