# Top-rated ScreenCasts

Text Section | Link to original post | Rating (out of 100) | Number of votes | Copy of rated post |
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09.05 - Fugacity and Fugacity Coefficient | Click here. | 100 | 1 |
What is fugacity? (10min) (learncheme.com) Defines fugacity in terms of Gibbs Energy and describes the need for defining this new property as a generalization of how pressure affects ideal gases. |

09.04 - Changes in Gibbs Energy with Pressure | Click here. | 100 | 1 |
Gibbs Energy - Nuts to Soup. (learncheme.com, 8min) It is straightforward to start from the definition of Gibbs Energy and derive all the changes in Gibbs energy. These can be graphed for H2O to see how familiar quantities from the steam tables relate to changes in this unfamiliar property. |

08.02 - The Internal Energy Departure Function | Click here. | 100 | 1 |
Departure Function Derivation Principles (8:03) (msu.edu) |

10.07 - Nonideal Systems | Click here. | 100 | 1 |
This screencast shows how to quickly visualize Pxy phase diagrams for nonideal systems using Excel (5min, uakron.edu). These A_{12}*x_{1}*x_{2}. Rigors of this model are discussed in Chapter 11. Nevertheless, its basic elements are simple enough that they can be understood in Chapter 10. When x1=0 or x2=0, a pure fluid is indicated, corresponding to no mixing and zero heat of mixing. When A12=0, the ideal solution approximation is recovered. When A12>0, the model indicates an endothermic interaction (like 2-propanol+water, Fig. 10.8c), giving rise to "positive deviations from Raoult's Law." When A12<0, the model indicates an exothermic interaction (like acetone+chloroform, Fig. 10.9c), giving rise to "negative deviations from Raoult's Law." With this spreadsheet, you can quickly change your components and A12 values to see how the phase diagram changes and gain "hands-on" familiarity with the principles discussed in Section 10.7. Note: This is a companion file in a series. You may wish to choose your own order for viewing them. For example, you should implement the first three videos before implementing this one. Also, you might like to see how to quickly visualize the Txy analog of the Pxy phase diagram. If you see a phase diagram like the ones in section 11.8, you might want to learn about LLE phase diagrams. The links on the software tutorial present a summary of the techniques to be implemented throughout Unit3 in a quick access format that is more compact than what is presented elsewhere. Some students may find it helpful to refer to this compact list when they find themselves "not being able to find the forest because of all the trees." Comprehension Questions: |

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 ΔG Comprehension Questions: (Hint: review Example 17.1 before answering.) 1. CO and H2 are fed in a |

17.05 - Effect of Pressure, Inerts, Feed Ratios | Click here. | 100 | 1 |
Partial pressures and reactor sizing are among the keys to chemical engineering calculations (uakron.edu, 7 min, review from Section 1.6). Partial pressures (uakron.edu, 7 min) also play an essential role in reaction equilibrium calculations. Partial pressure calculations basically involve straightforward mass balances, but specific vocabulary and a need for systematic precision can cause difficulty. The calculations involve six elements that must be carefully computed:
(1) Stoichiometry - the reaction equation must be stoichiometrically balanced such that the number of atoms of each element are the same on both sides of the equation. This balance is achieved by adjusting the stoichiometric coefficients. The change in the number of moles of each component must be in correct stoichiometric proportions relative to the "key component." Inert compounds (see below) are NOT included in the stoichiometric equation. For the example in this presentation, the objective of the reactor is to oxidize carbon monoxide (CO) in a catalytic converter by reacting it with oxygen (O2). So, CO + 0.5 O2 = CO2.
Comprehension Questions:
1. What is the value of the total pressure (bar) applied in the presentation of this example? |

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? |

11.02 - Calculations with Activity Coefficients | Click here. | 100 | 3 |
Bubble Temperature (2:43) (msu.edu) The culmination of the activity coefficient method is application of the fitted activity coefficients to extrapolate from limited experiments in a Stage III calculation. The bubble temperature is the easiest after bubble pressure. The recommended order of study is 1) Bubble Pressure; 2) Bubble Temperature; 3) Dew Pressure; 4) Dew Temperature. Note that an entire Txy diagram can be generated with bubble temperature calculations; no dew calculations are required. |

10.08 - Concepts for Generalized Phase Equilibria | Click here. | 100 | 1 |
Concepts for General Phase Equilibria (12:33) (msu.edu) The calculus used in Chapter 6 needs to be generalized to add composition dependence. Also, we introduce partial molar properties and composition derivatives that are not partial molar properties. We introduce chemical potential These concepts are used to show that the chemical potentials and component fugacities are used as criteria for phase equilibria. |

10.07 - Nonideal Systems | Click here. | 100 | 1 |
Nonideal Mixtures (4:58) (msu.edu) Raoult's law is an easy way to calculate VLE, but it is inaccurate for most detailed VLE calculations. This screencast provides an overview of the problems, and introduces the concept of an azeotrope. The VLE K-ratio is shown to be less than one or greater than one dependenting on the overall system concentration relative to the azeotrope composition where K=1. The concept of positive and negative deviations is introduced. |