# Top-rated ScreenCasts

Text Section | Link to original post | Rating (out of 100) | Number of votes | Copy of rated post |
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03.6 - Energy Balance for Reacting Systems | Click here. | 60 | 1 |
Heat Removal from a Chemical Reactor (uakron, 8min) determines heat removal so that a chemical reactor is isothermal following the pathway of Figure 3.5b using the pathway of Figure 2.6c if a heat of vaporization is involved. The reaction is: N2 + 3H2 = 2NH3 at 350C and 1 bar. The pathway to go from products to the reference condition is to correct for any liquid formation at the conditions of the product stream then cool/heat the products to 25C (the reference temperature), then "unreact" them back to their elements of formation. Summing up the enthalpy changes over these steps gives the overall enthalpy of the reactor outlet stream. The same procedure applied to the reactor inlet gives the overall enthalpy of reactor inlet stream. Then the heat duty of the reactor is simply the difference between the two stream enthalpies. Comprehension Questions: |

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 | 8 |
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. | 60 | 2 |
Heat Engine Introduction (LearnChemE.com, 6min) introduction to Carnot heat engine and Rankine cycle. 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, Comprehension Questions: |

08.07 - Implementation of Departure Functions | Click here. | 60 | 2 |
Helmholtz Departure - PR EOS (uakron.edu, 11min) This lesson focuses first and foremost on deriving the Helmholtz departure function. It illustrates the application of integral tables from Apx. B and the importance of applying the limits of integration. It is the essential starting point for deriving properties involving entropy (S,A,G) of the PREOS, and it is a convenient starting point for deriving energetic properties (U,H). |

05.5 Liquefaction | Click here. | 60 | 2 |
Joule-Thomson Expansion (LearnChemE.com, 7min) describes the Joule-Thomson coefficient - ( Comphrehension Questions: 1. Referring to the table for R134a in Appendix E-12, compute the fraction liquid at 252K after throttling from a saturated liquid at 300K. 2. Referring to the table for R134a in Appendix E-12, compute the fraction liquid at 252K after expanding a saturated liquid at 300K through a reversible turbine. |

01.2 Molecular Nature of Temperature, Pressure, and Energy | Click here. | 57.1429 | 14 |
Molecular Nature of Internal Energy: Configurational Energy. (uakron.edu, 19min) Making the connection between " U."
Comprehension Questions:
For 1-4, assume 100 molecules are held in a cylinder with solid walls. A piston in the cylinder can move to adjust the density. RT increase, decrease, or stay the same?5. Molecules A and B can be represented by the square-well potential. For molecule A, σ = 0.2 nm and ε = 30e-22 J. For molecule B, σ = 0.35 nm and ε = 20e-22 J. Sketch the potential models for the two molecules on the same pair of axes clearly indicating σ's and ε's of each species. Start your x-axis at zero and scale your drawing properly. Make molecule A a solid line and B a dashed line. Which molecule would you expect to have the higher boiling temperature? (Hint: check out Figure 1.2.) 6. Sketch the potential and the force between two molecules vs. dimensionless distance, r/σ, according to the Lennard-Jones potential. Considering the value of r/σ when the force is equal to zero, is it greater, equal, or less than unity? |

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.