Download presentation
1
Solution thermodynamics theory—Part III
Chapter 11
2
When we deal with mixtures of liquids or solids
We define the ideal solution model Compare it to the ideal gas mixture, analyze its similarities and differences
3
The ideal solution model
Component i in a mixture of ideal gases That is obtained by using In the first term of this equation Now we define Ideal solution model
4
Other thermodynamic properties for the ideal solution: partial molar volume
5
partial molar entropy in the ideal solution
6
partial molar enthalpy in the ideal solution
7
Chemical potential ideal solution
Chemical potential component i in a Real solution Chemical potential Pure component i Subtracting: For the ideal solution
8
Lewis-Randall rule Lewis-Randall rule
9
When is the ideal solution valid?
Mixtures of molecules of similar size and similar chemical nature Mixtures of isomers Adjacent members of homologous series
10
problem For the system methane (1)/ethane (2)/propane (3) as a gas, estimate at T = 100oC, P = 35 bar, y1 =0.21, and y2 =0.43 Assume that the mixture is an ideal solution Obtain reduced pressures, reduced temperatures, and calculate
11
Results: methane (1) ethane (2) propane (3)
Virial model Ideal solution
12
Now we want to define a new type of residual properties
Instead of using the ideal gas as the reference, we use the ideal solution
13
Excess properties The most important excess function is
the excess Gibbs free energy GE Excess entropy can be calculated from the derivative of GE wrt T Excess volume can be calculated from the derivative of GE wrt P And we also define partial molar excess properties
15
Definition of activity coefficient
16
Summary
17
Summary
18
Note that:
19
problem a) Find expressions for ln g1 and ln g2 at T and P
The excess Gibbs energy of a binary liquid mixture at T and P is given by a) Find expressions for ln g1 and ln g2 at T and P Using x2 =1 – x1 GE/RT= x x x13
20
Since gi comes from We can use eqns and 11.16
21
then And we obtain
22
If we apply the additivity rule and the Gibbs-Duhem equation
At T and P (b and c) Show that the ln gi expressions satisfy these equations Note: to apply Gibbs-Duhem, divide the equation by dx1 first
23
Plot the functions and show their values
GE/RT ln g1 ln g2
27
HW # 5, Due Monday, October 1 HW # 6, Due Monday, October 8
Problems 11.29, 11.30: cases d and e, 11.36, 11.37: case a, 11.38: case d, and 11.41 HW # 6, Due Monday, October 8 Problems TBA
Similar presentations
© 2024 SlidePlayer.com Inc.
All rights reserved.