1. Topic 4 The thermodynamics of mixtures
Key point: Solution

2. Is the properties of substances in a mixture the same as being single component?
Why?
Yes or No
The same person, would be in the same character in different groups?

3. The interaction between molecules
A+B
A-A B-B A-B A B +
B-B
A-A
Solution
A-A ≈B-B
A-A < B-B
A-A > B-B
Ideal solution
A-B ≈ A-A≈B-B
A-B ≠A-A ≠ B-B
Real solution
Composition of solution: m(mol.kg-1) , c(mol.L-1), w(g/kg) , x
Small amount of solute B/large amount solvent A----Deluted solutions A-B/A-A

4. Ideal solutions
(1)
(2)
(3)
(4)

5. Description of properties of mixtures
Components in a solution: 1,2, 3….k
Induced by composition variation
Z: U, H, S, A, G….

6. 4.1 Definition of partial molar quantities
Constant T and P
partial molar quantity of substance i

7. Description of properties of solutions
B: any component in the solution
Gibbs-Duhem equation
Binary system: A,B

8. Partial molar volume : Meaning, measurement and application
Example: ethanol+water=alcohol
Binary system:A,B V nB
Measurement

9. 4.2 Partial molar Gibbs energy: chemical potential μ ---By Gibbs and Lewis
At constant temperature and pressure, ( )T,P

10. Thermodynamic relationship for mixed system

11. The new justification for composition variation of mixed system
The maximum efficient (non-expansion ) work
The drive force of the composition variation of mixed system
The energy resource of doing work

12. Example 1: Phase equilibrium
A:Water B:CCl a: I2
a/B
a/A
dna
Happen if
It can happen
Get equilibrium
The reverse process can happen
The chemical potential of the same substance in different phases being in equilibrium are equal

13. Example 2: Chemical reaction
A,B
A,B,C
νAA+νBB→νCC
If dζ
Initial
It can happen
Get equilibrium
The reverse process can happen
The drive force of chemical reaction

14. 4.3 Chemical potentials of substances
(1) Pure ideal gases
Chemical potential at standard state

15. (2) Mixed ideal gases
Chemical potential of pure B at T,P
(3) For real gases
(4) For mixed real gases

16. < (5) Pure liquids Gas-liquid phase equalibrium 100℃,PΘ,H2O(l)
Comparing the chemical potentials:
100℃,PΘ,H2O(l)
100℃,PΘ,H2O(g)
100℃,2PΘ,H2O(l)
100℃,PΘ,H2O(g)
100℃,PΘ,H2O(l)
100℃,2PΘ,H2O(g)
100℃,2PΘ,H2O(g)
100℃,2PΘ,H2O(l)
<

17. (6) Mixed liquids---solutions
PB = ?
Raoult’s law and Henry’s law

18. 4.4 Raoult’s law and Henry’s lawP
A(solvent)
B(solute)
Gas A, (B)
liquid
P total
Raoult’s law xA
For ideal solution A solvent B solute
For real solution

19. Chemical potential of components of ideal solutions
For real solutions

20. Henry’s Law Relating Kx,B and A-A interaction is stronger than B-B
A(solvent)
B(solute)
Gas A, B
liquid xB
kx,B A B
xB很小时
xB很大时 p
Relating Kx,B and
A-A interaction is stronger than B-B
B is easier to vaporize
Kx,B >
A-A interaction = B-B
Kx,B =

21. Ideal diluted solution
Solvent follow Raoult’s law
Solute follow Henry’s law

22. Homework Excises: A: P191:7.4 7.9 P93: 5 P98: 11 Preview:
Examples and explanation of Colligative properties of diluted solution
Y:3.6,3.7 A:
Excises:
A: P191:
P93: 5
P98: 11