Top-rated ScreenCasts

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01.6 Summary Click here. 100 1

Keys to the Kingdom of Chemical Engineering (uakron.edu, 11min) Sometimes it helps to reduce a subject to its simplest key elements in order to "see the forest instead of the trees." In this presentation, the entire subject of Chemical Engineering is reduced to three key elements: sizing a reactor (Uakron.edu, 7min), sizing a distillation column (uakron.edu, 9min), and sizing a heat exchanger (uakron.edu, 9min). In principle, these elements involve the independent subjects of kinetics, thermodynamics, and transport phenomena. In reality, each element involves thermodynamics to some extent. Distillation involves thermodynamics in the most obvious way because relative volatility and activity coefficients are rarely discussed in a kinetics or transport course. In kinetics, however, the rate of reaction depends on the partial pressures of the reactants and their nearness to the equilibrium concentrations, which are thermodynamical quantities. In heat exchangers, the heat transfer coefficient is important, but we also need to know the temperatures for the source and sink of the heat transfer; these temperatures are often dictated by thermodynamical constraints like the boiling temperature or boiler temperature required to run a Rankine cycle (cf. Chapter 5). In case you are wondering about the subject of "mass and energy balances," the conservation of mass is much like the conservation of energy; therefore, we subsume this subject under the general umbrella of thermodynamics. Understanding the distinctions between thermodynamics and other subjects should help you to frame a place for this knowledge in your mind. Understanding the interconnection of thermodynamics with subjects to be covered later should help you to appreciate the necessity of filing this knowledge away for the long term, such that it can be retrieved at any time in the future.

If you would like a little more practice with reactor mass balances and partial pressure, more screencasts are available from LearnChemE.com, MichiganTech, and popular chemistry websites.
10.02 - Vapor-Liquid Equilibrium (VLE) Calculations Click here. 100 2

VLE Routines - General Strategies (4:49) (msu.edu)

Deciding which routine to use is more challenging than it appears. Also understanding the strategy used to solve the problems is extremely helpful in being able to develop the equations to solve instead of trying to memorize them.
14.09 - Numerical procedures for binary, ternary LLE Click here. 100 1

LLE Calculations: UNIFAC from Actcoeff.xlsx Calculation of LLE. (5 min) (LearnChemE.com)
See also - Supplement on Iteration of LLE with Excel and Matlab. Hints on converging LLE using Excel with the method presented in the textbook. For details, see
17.07 - Temperature Dependence of Ka Click here. 100 2

You can customize Kcalc.xlsx (uakron.edu, 17min) to facilitate whatever calculations you may need to perform. This presentation shows how to implement VLOOKUP to automatically load the relevant Hf, Gf, and Cp values. It also shows how to automatically use the Cp/R value when a,b,c,d values for Cp are not available. Finally, it shows how a fairly general table of inlet flows, temperatures, and pressures can be used to set up the equilibrium conversion calculation. The initial set up is demonstrated for the dimethyl ether process, then revised to initiate solution of Example 17.9 for ammonia synthesis.

Comprehension Questions:

1. The video shows how the shortcut Van't Hof equation can be written as lnKa=A+B/T. What are the values of A and B for the dimethyl ether process when a reference temperature of 633K is used?
2. The video shows how the shortcut Van't Hof equation can be written as lnKa=A+B/T. What are the values of A and B for the ammonia synthesis process when a reference temperature of 600K is used?
17.06 Determining the Spontaneity of Reactions Click here. 100 1

Which way will a reaction go? (3:40) (msu.edu)

When both reactants and products are present in a reactng mixture, the direction the reaction will proceed is not necessarily indicated by the sign of ΔGo or Ka. Rather, it is determined by ΔG. This screencasts provides guidance for understanding this concept.

Comprehension Questions: (Hint: review Example 17.1 before answering.)

1. CO and H2 are fed in a 2:1 ratio to a reactor at 500K and 20 bars with a catalyst that favors only CH3OH as its product. When the conversion of H2 is 32%, will the reaction go forwards towards product or back to reactants?
2. CO and H2 are fed in a 2:1 ratio to a reactor at 500K and 20 bars with a catalyst that favors only CH3OH as its product. When the conversion of CO is 52%, will the reaction go forwards towards product or back to reactants?
3. CO and H2 are fed in a 1:1 ratio to a reactor at 500K and 20 bars with a catalyst that favors only CH3OH as its product. When the conversion of H2 is 42%, will the reaction go forwards towards product or back to reactants?
4. CO and H2 are fed in a 1:1 ratio to a reactor at 500K and 20 bars with a catalyst that favors only CH3OH as its product. When the conversion of H2 is 42%, will the reaction go forwards towards product or back to reactants?
07.02 Corresponding States Click here. 100 1

Principles of Corresponding States (10:02) (msu.edu)
An overview of use of Tc and Pc and acentric factor to create corresponding states correlation. The relation between acentric factor and deviations from spherical fluids is highlighted.

Comprehension Questions:

1. What is the value of the reduced vapor pressure for Krypton at a reduced temperature of 0.7? How does this help us to characterize the vapor pressure curve?

2. Sketch the graph of vapor pressure vs. temperature as presented in this screencast for the compounds: Krypton and Ethanol. Be sure to label your axes completely and accurately. Draw a vertical line to indicate the condition that defines the acentric factor.
14.09 - Numerical procedures for binary, ternary LLE Click here. 100 1

LLE flash using Matlab/Chap14/LLEflash.m (5:54) (msu.edu)

An overview of the LLE flash routine in Matlab, including an overview of the program logic and then an example of how to run the program.

See also - Supplement on Iteration of LLE with Excel and Matlab.
17.05 - Effect of Pressure, Inerts, Feed Ratios Click here. 100 1

How to push, pull, persuade a reaction (3:32) (msu.edu)

Pressure can be used to influence conversion for reactions where gas phase species are present. Feed ratios, inerts, or simultaneous reactions can also be used.

Comprehension Questions:

1. The principle by which a change in temperature, pressure, or concentration leads to a counteracting change in equilibrium is known as:_____.
2. For the reaction: CO + 2H2 = CH3OH, an increase in pressure will cause the products to: ___ (decrease, increase, or be unaffected). Explain.
2. For the reaction: CH4 + H2O = CO + 3H2, an increase in pressure will cause the products to: ___ (decrease, increase, or be unaffected). Explain. (FYI: this reaction, known as "steam reforming" is an important step in making chemicals from natural gas.)
3. For the reaction: CO + 2H2 = CH3OH, adding an inert component will cause the products to: ___ (decrease, increase, or be unaffected). Explain.
4. We discuss temperature effects in detail later, but for now you should be able to make predictions based on ____ principle (cf. #1 above). An exothermic reaction gives off heat. Therefore, adding heat to an exothermic reaction (ie. raising the temperature) will cause the products to: ___ (decrease, increase, or be unaffected). Explain.
5. For the reaction: H2O + CO = H2 + CO2, an increase in pressure will cause the products to: ___ (decrease, increase, or be unaffected). Explain. (As a first approximation, you may neglect deviations from ideal gas behavior, but then discuss the effect these deviations would have if you did take them into account. Which component's fugacity would be most affected by these deviations and how do these deviations change with pressure?)
6. For the reaction: coal + H2O = CO + H2, an increase in pressure will cause the products to: ___ (decrease, increase, or be unaffected). Explain. (Hint: carbon in the form of coal is solid and does not exist in the vapor phase. cf. section 17.14. It might be helpful to think of the reverse reaction, known as coking, where the solid carbon precipitates from the gas. This is a very simple example of simultaneous reaction and phase equilibrium.)
7. For the reaction: CO + 2H2 = CH3OH, adding an inert liquid to the reactor through which all products are removed will cause the products to: ___ (decrease, increase, or be unaffected). Explain. (Hint: this is a bit more sophisticated example of simultaneous reaction and phase equilibrium. How will the inert liquid alter the concentrations in the vapor? Remember that the fugacities are proportional to the gaseous partial pressures.)
08.02 - The Internal Energy Departure Function Click here. 100 1

Departure Function Derivation Principles (8:03) (msu.edu)
This screencast covers sections 8.2 - 8.8. Concepts of using the equation of state to evaluate departure functions. The screencasts also discusses the choice of density integrals or pressure integrals. The use of a reference state is discussed.
13.04 - UNIQUAC Click here. 100 2

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.

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