1.9.4. Enthalpy-Concentration, Liquid-Gas-Concentration-Diagrams of Ethanol-Water Mixtures

This example explains, how you can plot state diagrams (e.g. xy-diagrams as following picture) using the empirical equations of activity coefficients in the application Equilibrium.


There is x the concentration in liquid- and y in the gas phases.
Step by Step:
1.9.4.1. Elements
Main Menu: System -> Elements. Selection: C,H,O

1.9.4.2. Compounds
In the window for Gas, Select Compounds C2H5OH(g) and H2O(g)
In the window for Liquid, Select Compounds C2H5OH(l) and H2O(l)

1.9.4.3. Activity Coefficients
Main Menu: System -> Activity Coefficients
Select the logarithmic equations of van Laar in drop-down button as shown in the following picture.
Enter coefficients A and B, press Button Add



Equation 1 is the activity coefficients of  ethanol  and Equation  2  is the activity coefficient of water in binary mixtures of liquids at 50°C corresponding van Laar
(the constants A and B are given by C.A. Jones, A.P. Schoenborn, Ind. Chem. Eng. 40 (1940) 1273-1276).

1.9.4.4. Record Variables
Main Menu: Monitoring -> Record Definition
Select the concentration of the ethanol and water in liquid and gas phase. You can select also other variables to record




1.9.4.5. Graphic Variables
Main Menu: Monitoring -> Graphic Variables
You can determine, which variables are in which coordinates to show in the Graphic Window.



1.9.4.6.  Assignment of the Equations for Activity Coefficients to Substances Ethanol and Water
Enter for activity coefficient of ethanol [1] , and  for activity coefficient water [2] in the columns a.c. in the phase table corresponding the definition of the equations for activity coefficients in Chapter 1.9.4.3.



1.9.4.7. Calculation
Main Menu: System -> Calculation by Variation




Insert as variables :
Input  Liquid 1 C2H5OH (l) from 0 to 1 with steps +0.01
Input  Liquid 1 H2O (l) from 1 to 0 with steps -0.01
Start the calculations.

1.9.4.8. The results of the calculations will be shown in Graphic Window

Enthalpy-concentration diagram of ethanol-water-mixtures



xy-Diagram Ethanol-Water Mixtures



Course of the activity coefficients in ethanol-water mixtures corresponding given data in Chapter 1.9.4.3.