# Top-rated ScreenCasts

Text Section | Link to original post | Rating (out of 100) | Number of votes | Copy of rated post |
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09.10 - Saturation Conditions from an Equation of State | Click here. | 60 | 2 |
Solving for the saturation pressure using PREOS.xls simply involves setting the temperature and guessing pressure until the fugacities in vapor and liquid are equal. (5min, learncheme.com) It is not shown, but it would also be easy to set the pressure and guess temperature until the fugacities were equal in order to solve for saturation temperature. One added suggestion would be to type in the shortcut vapor pressure (SCVP) equation to give an initial estimate of the pressure. Rearranging the SCVP can also give an initial guess for Tsat when given P. This presentation illustrates a Comprehension Questions: 1. Estimate the vapor pressure (MPa) of n-pentane at 450K according to the PREOS. Compare your result to the value from Eq. 2.47 (SCVP) and to the Antoine equation using the coefficients given in Appendix E. What do you think explains the observations that you make? |

10.03 - Binary VLE using Raoult's Law | Click here. | 60 | 4 |
Raoult's Law Calculation Procedures (11:45) (msu.edu) Comprehension Questions: Assume the ideal solution SCVP model (Eqns. 2.47 and 10.8). 1. Estimate the bubble pressure (bars) of 30% acetone + 70% benzene at 333K. |

09.10 - Saturation Conditions from an Equation of State | Click here. | 60 | 1 |
We can combine the definition of fugacity in terms of the Gibbs Energy Departure Function with the procedure of visualizing an equation of state to visualize the fugacity as characterized by the PR EOS. (21min, uakron.edu) This amounts to plotting Z vs. density, similar to visualizing the vdW EOS. Then we simply type in the departure function formula. Since the PR EOS describes both vapors and liquids, we can calculate fugacity for both gases and liquids. Taking the reciprocal of the dimensionless density (
Concept Questions:
1. What equation can we use to estimate the fugacity of a compressed liquid relative to its saturation value? |

14.04 LLE Using Activities | Click here. | 60 | 2 |
Txy Phase Diagram Showing LLE and VLE Simultaneously (9min,uakron.edu) The binary Txy phase diagram of methanol+benzene is visualized with k) increases, the LLE boundary crashes into the VLE. It is so exciting that it makes a thermo nerd wax poetic about the "valley of Gibbs."_{ij}Comprehension Questions: 1. The LLE phase boundary moves up as the nonideality increases. Which way does the VLE contribution move? Explain how this relates to the molecules' escaping tendencies. 4. What value of kis required to make the LLE binodal barely touch the VLE at 10 bars?_{ij } |

07.08 Matching The Critical Point | Click here. | 60 | 2 | |

01.5 Real Fluids and Tabulated Properties | Click here. | 60 | 2 |
Steam Tables (LearnChemE.com) (5:59) calculate enthalpy of steam by interpolation |

11.12 - Lewis-Randall Rule and Henry's Law | Click here. | 60 | 11 |
Introduction to Henry's Law (10:16) (msu.edu) Fugacities are calculated relative to standard state values, and the relations developed earlier in the chapter use a pure fluid standard state. What if the pure fluid does not exist as a liquid when pure? One choice is to use Henry's law. |

11.13 - Osmotic Pressure | Click here. | 60 | 9 |
Osmotic Pressure (7:23) (Learncheme.com) A derivation of the relation for osmotic pressure, and an explanation of why the pressures are different on each side of the semi-permeable membrane. |

07.06 Solving The Cubic EOS for Z | Click here. | 60 | 4 |
2. Solving the PR EOS for Z . (learncheme.com, 5min) Shows how to copy/paste from "Crit.Props" and "IG Cps" to "Props". Then compute some properties. Note: this video incorrectly uses a simple copy/paste instead of "paste special." Therefore, the color of the values on the "Props" tab changes from blue to black. Blue values should indicate values that you can change and black values should indicate cells that you should not alter. If you are having trouble finding a particular compound in the database, try searching for a piece of the name. e.g. if the compound is "nitrous oxide," search for "nitro." Comprehension Questions: 1. What is the value for Zc of nitrous oxide? What is its "abbreviated name?" 2. What is the value of Tc for R1234yf? 3. Estimate the entropy of vaporization of toluene at 383.4K according to the Peng-Robinson EOS. 4. Estimate the entropy of vaporization of ethanol at 0.1MPa according to the Peng-Robinson EOS. Compare to the value you infer from Appendix E. |

03.1 - Heat Engines and Heat Pumps: The Carnot Cycle | Click here. | 56.6667 | 6 |
Introduction to the Carnot cycle (Khan Academy, 21min). The Carnot cycle is an idealized conceptual process in the sense that it provides the maximum possible fractional conversion of heat into work (aka. thermal efficiency, η = (_{θ}T)/_{H} - T_{C}TH, where Tis the hot temperature and _{H} Tis the cold temperature. We can use this formula to quickly estimate the thermal efficiency for many processes. We will show in Chapter 5 that this formula remains the same, even when we use working fluids other than ideal gases (e.g. steam or refrigerants)._{C }Comprehension Questions: 4. What value of Twould be necessary to approach 100% efficiency, even for this idealized, maximally efficient process? What are the practical limitations on _{H} T? Explain. _{H}5. How can the formula for Carnot efficiency help us to calculate the "lost" work in the presence of a temperature gradient? |

Visualizing the vdW EOS (uakron.edu, 16min) Building on solving for density, describes plotting dimensionless isotherms of the vdW EOS for methane at 5 temperatures, two subcritical, two supercritical, and one at the critical condition. From these isotherms in dimensionless form, it is possible to identify the critical point as the location of the inflection point where the temperature first exits the 3-root region. This method can be adapted to any equation of state, whether it is cubic or not. The illustration was adapted from a

sample test problem. This screencast also addresses the meaning of the region where the pressure goes negative, with a (possibly disturbing) story about a blood-sucking octopus.Comprehension Questions:

1. What are the dimensions of the quantity (

bP/RT)?2. Starting with the expression for

Z(ρ,T), rewrite the vdW EOS to solve for the quantity (bP/RT) in terms of (bρ) and (a/bRT).3. Consider the following EOS:

Z= 1 + 2bρ/(1-2bρ) - (a/bRT) /(1-bρ)^{2}. Estimate the value ofbP_{c}/(RT_{c}) for this EOS.4. Consider the following EOS:

Z= 1 + 2bρ/(1-2bρ) - (a/bRT) /(1-bρ)^{2}. Estimate the value of (a/bRT) for this EOS._{c}5. Compute the values of

a(J-cm^{3}/mol^{2}) andb(cm^{3}/mol) for methane according to this new EOS.