Local Composition Concepts (6:51) (msu.edu)

The local composition models of chapter 13 share common features covered in this screencasts. An understanding of these principles will make all the algebra in the models less daunting.

Comprehension Questions:

1. In the picture of molecules given in the presentation on slide 2, what is the numerical value of the local composition x₁₁?
2. In the same picture, what is overall composition x₁?
3. What value of Ω₂₁ can you infer from 1 and 2 above and the equations on slide 3?

Wilson's model concepts (2:44) (msu.edu)

The background on the assumptions and development of Wilson's activity coefficient model.

Comprehension Questions:

1. What value is assumed by Wilson's model for the coordination number (z)?
2. What are the values of Λ₂₁ and Λ₁₂ at infinite temperature, according to Wilson's equation?
3. Solve for x₁+x₂Λ₁₂ in terms of volume fraction (Φ₁) and mole fraction (x₁) at infinite temperature.
4. What type of phase behavior is impossible to represent by Wilson's equation?

NRTL concepts (2:30) (msu.edu)

The concepts on the development of the NRTL activity coefficient model.

Comprehension Questions:

1. What value does the NRTL model assume for the coordination number (z)?
2. What does the acronym "NRTL" stand for?
3. What is the relation between τ₁₂, τ₂₁, and A₁₂ of the M1 model when α₁₂=0?
4. The NRTL model has one more parameter than the Wilson model. Which parameter is it and what is its default value?

UNIQUAC concepts (6:44) (msu.edu)

Concepts and assumptions used in developing the UNIQUAC activity coefficient method. This method introduced the use of surface area as an important quantity in calculation of activity coefficients.

Volumes and Areas from Group Contributions (3:04)

Group contributions are used widely in property prediction. The volumes and surface areas have been determined by x-ray data and high-temperature collision data. The UNIQUAC and UNIFAC activity coefficient methods use these quantities to calculation volume fractions and surface area fractions. The assignment of functional groups for a molecule must be done carefully to assure agreement with the groups used by the model developers.

Comprehension Questions:

1. Estimate R and Q for 1,4 dihydroxy benzene.

2. Estimate R and Q for n-propyl alcohol and compare them to the values for IPA.

3. Estimate R and Q for methyl-npropyl ketone.

Unifac.xls Calculation of Bubble Temperature. (3 min) (LearnChemE.com)
Comprehension Questions: Download Unifac.xls from the software link and use it to answer the following.
1. Estimate the activity coefficient of IPA in water at 80C and xw = 0.1.
2. Estimate the fugacity for IPA in water at 80C and xw =0.1.
3. Estimate the total pressure at 80C when xw =0.1.
4. Estimate the bubble temperature of IPA in water at 760mmHg and xw =0.1.

UNIFAC concepts (8:17) (msu.edu)

UNIFAC is an extension of the UNIQUAC method where the residual contribution is predicted based on group contributions using energy parameters regressed from a large data set of mixtures. This screecast introduces the concepts used in model development. You may want to review group contribution methods before watching this presentation.

Comprehension Questions:

1. What is the difference between the upper case Θ of UNIFAC and the lower cast θ of UNIQUAC?

2. Suppose you had a mixture that was exactly the same proportions as the lower right "bubble" in slide 2. Compute Θ_OH for that mixture.

3. Compare your value computed in 2 to the value given by unifac.xls.