1. Thermodynamic Consistency
Avi Vegda ( )
Ankit Vashi( )
Parth Patel( )
Guided By
Janki Tailor

2. Thermodynamic Consistency
The Gibbs/Duhem Equation imposes a constraint on activity coefficient that may not be satisfied by a set of experimental values derived from P-xy data.
The experimental values of ln γ1 and ln γ2 combine by (excess Gibbs free energy) to give values of GE/RT.
This addition process is independent of the Gibbs/Duhem Equation.

3. Nor can a P-xy correlation Calculated by modify Roults low be consistent with experimental values.
If the experimental data are inconsistent with the Gibbs/Duhem equation , they are necessarily incorrect as the result of systematic error in the data.
Because correlating equations for GE/RT impose consistency on derived activity coefficients, no such correlation exists that can precisely reproduce P-xy data that are inconsistent.
Our purpose now is to develop a simple test for the consistency with respect to the Gibbs/Duhem equation of a P-xy data set.

7. Using slope in curve
Gibb’s- duhem eqn

8. To verify consistancy exit or not plot,
graph

9. Using Mid-Point Data
In Van- Laar eqn.
put

11. at

12. Redlich/ Kister method
Diff … w.r.t x1

13. Now ,
In between x1=0 to x2=1

14. at
Plot Vs

16. Using coexistence equation:-
Modified Raoult’s law
consider vap. Phase is ideal gas
Gibbs/Duhem equation

17. at const T. by Antion eqn.

18. (5) Using Partial pressure data [ low pressure system] Gibbs/Duhem equation

20. Thank You…