1. Classical Thermodynamics of Solutions
Lecture 17
Classical Thermodynamics of Solutions
Gibbs free energy of formation of solution
Ideal gas mixtures
Ideal, dilute and concentrated solutions
Excess functions

2. Gibbs free energy of mixing, GM
XA mol of A + XB mol of B
Since
Therefore
But
Thus finally or

3. Ideal gas activity and GM
Activity for a gas is
Where is arbitrary. We can choose
For which
And the Gibbs free energy of mixing

4. Ideal gas - HM, and SM
Since X is independent from temperature. From this the entropy of mixing of an ideal solution

5. Multicomponent condensed phases
Chemical potential of a vapor
For the solid
In equilibrium, distributive equilibrium
From which since in equilibrium

6. Ideal solution
For ideal solution
From which
And

7. Dilute solution
Pressure above dilute solute is proportional to its concentration
From which
Where
Is the activity coefficient can be greater or smaller than one. It is 1 for ideal solutions.

8. Dilute solution - II Gibbs Duhem At constant T and P
In terms of molar properties
Thus for dilute solution of B in A

9. Dilute solution - III Recalling that And with
Since activity coefficient is constant

10. Dilute solution - IV After differentiating the second term
After integration since

11. Concentrated solutions
Activity coefficient is not a constant any more
However, for so-called regular solutions we still assume entropy of mixing same as for the ideal solution
But the enthalpy of mixing will be not zero.

12. Excess functions Chemical potential of mixing For an ideal solution
Which defines excess chemical potential of mixing
Or in terms of partial molar from which