# Top-rated ScreenCasts

Text Section | Link to original post | Rating (out of 100) | Number of votes | Copy of rated post |
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13.05 - UNIFAC | Click here. | 84 | 5 |
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 2. Suppose you had a mixture that was exactly the same proportions as the lower right "bubble" in slide 2. Compute Θ 3. Compare your value computed in 2 to the value given by unifac.xls. |

07.06 Solving The Cubic EOS for Z | Click here. | 83.3333 | 6 |
3. Using Preos.xlsx and Interpreting Output (11:38) (msu.edu) Comprehension Questions: 1. Is it possible to have a 1-root region below the critical temperature? 2. Is it possible to have a 3-root region above the critical temperature? 3. How does fugacity help us to identify the proper root to select? 4. Would argon at 5 MPa be in the 1-root or 3-root region? |

13.05 - UNIFAC | Click here. | 82.8571 | 7 |
Unifac.xls Calculation of Bubble Temperature. (3 min) (LearnChemE.com) |

15.04 - VLE calculations by an equation of state | Click here. | 80 | 1 |
PRMix.xlsx - Tutorial on use for bubble pressure (msu.edu) (10:06) An overview of the organization of PRMix.xlsx, and a tutorial on the strategy to solve bubble pressure problems. Example 15.6 is worked in the screencast. After watching this screencast, you should be able to also solve dew or flash problems if you think about the strategy used to solve the problem. You may also be interested in a similar presentation from U.Colorado (learncheme, 6min). |

10.10 - Mixture Properties for Ideal Solutions | Click here. | 80 | 1 |
10.9 - 10.12 Mixture Properties Overview (6:53) (msu.edu) This section of the text is thick with lots of equations. It may help to filter out the most important equations and results so that you have the perspective of the overall objectives of this section. There are a lot of equations in this section to show that the component fugacity in an ideal solution is simply the mole fraction multiplied by the pure component fugacity. In a liquid mixture, this is approximated as the mole fraction times the vapor pressure! This screencast goes on to preview the most important results of the next section to help you see the overall story. |

13.03 - NTRL | Click here. | 80 | 1 |
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)? |

18.09 - Sillen Diagram Solution Method | Click here. | 80 | 1 |
Sillen Diagram for Electrolyte Calculations (10:14) (msu.edu) Construction of a Sillien diagram involves several steps that are hard to follow from a textbook. This screencast goes through the steps of solving Example 18.5 from the Elliott and Lira textbook using the Sillen diagram. The problem asks for the pH of a solution that is 0.01 M NaOAc. |

12.03 - Scatchard-Hildebrand Theory | Click here. | 80 | 3 |
This video walks you through the process of transforming the M1/MAB model into the Scatchard-Hildebrand model using Excel (6min, uakron.edu) It steps systematically through the modifications to the spreadsheet to obtain each new model. You should implement the M1/MAB model before implementing this procedure. Comprehension Questions: |

07.05 Cubic Equations of State | Click here. | 80 | 1 |
Intro to the vdW EOS. (LearnCheme.com, 5min) Provides a brief overview of the van der Waals (vdW) 1873 equation of state (EOS), which served as a prototype for EOS development for over 100 years. Note: the vdW EOS is just one conjecture of how equations of state for real fluids may be formulated. In reality, each fluid has its own unique EOS. The vdW model conjectures that the pressure is altered relative to the ideal gas by the presence of attractive forces and repulsive forces. Comprehension Questions: 1. Of the two parameters |

01.2 Molecular Nature of Temperature, Pressure, and Energy | Click here. | 77.8947 | 19 |

Molecular Nature of Internal Energy: Thermal Energy

This introduction to "thermal energy" elaborates on the ideal gas definition of temperature, which derives from the way that

PVis related to kinetic energy. ThisPVrelation can be easily understood in terms of an ultrasimplified model of ideal gas pressure. (uakron, 6min). Noting empirically from the ideal gas law thatPV=nRT, we are led to the derivation of Eqn. 1.1 (uakron, 5min, same as above). This result suggests counter-intuitive implications about the the ways that solid, liquid, and gas molecular velocities must be related. When applying Eqn. 1.1, you must be careful to keep your units straight, as illustrated in this sample calculation of molecular temperature for Xenon (Mw=131g/mol) (uakron, 5min). On a closely related note, we could perform a sample calculation of molecular pressure for Xenon using Eqn. 1.21.Comprehension Questions:

1. If two phases are in equilibrium (e.g. a vapor with a solid), then their temperatures are equal and the rate at which molecules leave the solid equals the rate at which molecules enter the solid. Which molecules are moving faster, solid or vapor? For simplicity, assume that the vapor is xenon and the solid is xenon. Hint: think about the exchange of momentum when the vapor molecules collide with the solid.

2. Compute the average (root mean square) velocity (m/s) of molecules at room temperature and pressure and compare to their speeds of sound. You can search the internet to find the speed of sound.

a. Argon

b. Xenon

3. Three xenon atoms are moving with (x,y,z) velocities in m/s of (300,-450,100), (-100,300,-50), (-200,-150,-50). Estimate the temperature (K) of this fluid.

4. Estimate the pressure of the xenon atoms in Q3 above in a vessel that is 4nm

^{3}in size.