# Top-rated ScreenCasts

Text Section | Link to original post | Rating (out of 100) | Number of votes | Copy of rated post |
---|---|---|---|---|

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. |

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. | 78.1818 | 22 | |

01.2 Molecular Nature of Temperature, Pressure, and Energy | Click here. | 77.2727 | 66 |
Molecular Nature of Energy and Temperature (msu.edu) (3:34) Comprehension Questions: 1. A 1m3 vessel contains 0.5m3 of saturated liquid in equilibrium with 0.5 m3 of saturated vapor. Which molecules are moving slower? (a) the vapor (b) the liquid (c) they are all the same. 2. A glass of ice water is sitting in your freezer, set to 0C and fully equilibrated. Which molecules are moving slower? (a) the gas (b) the liquid (c) the solid (d) they are all the same. 3. You walk into the kitchen in the morning to get some breakfast. The ceiling fan is on. You forgot your slippers. Which one is "hotter?" (a) the floor (b) the ceiling (c) the granite counter top (d) the air in the room (e) they are all the same. |

08.02 - The Internal Energy Departure Function | Click here. | 73.3333 | 3 |
The Internal Energy Departure Function (11min, uakron.edu) Deriving departure functions for a variety of equations of state is simplified by transforming to dimensionless units and using density instead of volume. This also leads to an extra simplification for the internal energy departure function. Comprehension Questions: 1. What is the value of P for an ideal gas?2. What is the value of ( ∂U/∂V) for an ideal gas and how can you explain this result at the molecular scale?_{T}3. The Redlich-Kwong (RK) EOS is: P=RT/(V-b) -a/(V^{2}RT^{1.5}). Use Eqn. 8.13 to solve for (U-U)/^{ig}RT of the RK EOS.4. The RK EOS can be written as: Z = 1/(1-bρ) - aρ/(RT^{1.5}). Use Eqn. 8.14 to solve for (U-U)/^{ig}RT of the RK EOS. |

13.04 - UNIQUAC | Click here. | 73.3333 | 3 |
UNIQUAC concepts (6:44) (msu.edu) Concepts and assumptions used in developing the UNIQUAC activity coefficient method. This method introduced the use of surface area as an important quantity in calculation of activity coefficients. |

10.03 - Binary VLE using Raoult's Law | Click here. | 73.3333 | 3 |
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. |

07.05 Cubic Equations of State | Click here. | 73.3333 | 3 |
Virial and Cubic EOS (11:18) (msu.edu) Comprehension Questions: 1. To what region of pressure is the virial EOS limited at a given temperature? Why? |

04.02 The Microscopic View of Entropy | Click here. | 72 | 5 |
Principles of Probability III, Distributions, Normalizing, Distribution Functions, Moments, Variance. This screencast extends beyond material covered in the textbook, but may be helpful if you study statistical mechanics in another course. (msu.edu, 15min) (Flash) |

12.01 - The van der Waals Perspective for Mixtures | Click here. | 70 | 4 |
Mixing Rules (7:23) (msu.edu) How should energy depend on composition? Should it be linear or non-linear? What does the van der Waals approach tell us about composition dependence? This screencasts shows that the mixing rule for 'a' in a random mixture should be quadratic. A linear mixing rule is usually used for the van der Waals size parameter. |

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.