12.05 - MOSCED and SSCED Theory

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This video walks you through the process of transforming the Scatchard-Hildebrand model into the SSCED model using Excel (6min, uakron.edu) It steps systematically through the modifications to the spreadsheet to obtain the new model. You should implement the Scatchard-Hildebrand model before implementing this procedure.

Comprehension Questions:
1. Add Txy capability to this model.
2. Predict the Txy diagram for methanol+benzene by the SSCED model at 2222mmHg. Estimate the phase compositions and phase amounts for the following operating temperatures and feed compositions. (a) 370K and zm = 0.30 (b) 350K and zm = 0.20 (c) 370K and zm = 0.70.
3. Compare your predicted Txy diagram to the predictions by the MAB and Scatchard-Hildebrand models. Describe the differences briefly for each case.
4. Search for experimental data on the system ethanol+toluene. Modify your spreadsheets to plot the experimental data (points) on the same plot with the predictions. Which model provides the most accurate predictions when compared to data? 
5. Suppose you set k12=0 in the SSCED model. Does that improve the comparison to experimental data? Other models? Does the combination of k12=0 and k12=k12(alpha,beta) bracket the range of values that fit reasonably?

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There are so many activity models, how can you keep them straight? This video shows how MAB, SSCED, and Scatchard-Hildebrand models are all closely related.(9min,uakron.edu) By changing the assumptions, one model can be transformed into the other. So focus on remembering one model very well, then remember the small adjustments to obtain the other models.

Comprehension Questions:
1. Suppose we are trying to find the solvent most compatible with dilute ethanol. Which of the following is most compatible according to the MAB model?  (a) water (b) benzene (c) n-octanol.
2. Suppose we are trying to find the solvent most compatible with dilute ethanol. Which of the following is most compatible according to the ScHil model?  (a) water (b) benzene (c) n-octanol.
3. Suppose we are trying to find the solvent most compatible with dilute ethanol. Which of the following is most compatible according to the SSCED model?  (a) water (b) benzene (c) n-octanol. (Hint: consider the infinite dilution activity coefficient.)

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