Top-rated ScreenCasts

Text Section Link to original post Rating (out of 100) Number of votes Copy of rated post
07.06 Solving The Cubic EOS for Z Click here. 83.33329999999999 6

3. Using Preos.xlsx and Interpreting Output (11:38) (msu.edu)
This screencast includes discussion of what we mean by the casual terminology 'three root region' and 'one root region', and how to interpret screen output. Also, the screencast spends time dicussing selection of stable roots using fugacity.

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. 80 5

Unifac.xls Calculation of Bubble Temperature. (3 min) (LearnChemE.com)
Comprehension Questions: Download Unifac.xls from the software link and use it to answer the following.
1. Estimate the activity coefficient of IPA in water at 80C and xw = 0.1.
2. Estimate the fugacity for IPA in water at 80C and xw =0.1.
3. Estimate the total pressure at 80C when xw =0.1.
4. Estimate the bubble temperature of IPA in water at 760mmHg and xw =0.1.

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 a and b, which is related to attractive forces and which is related to attractive forces?
2. How are the parameters a and b typically characterized/computed? ie. To what experimental constants are they related in order to compute them?
3. Is the vdW EOS an example of a 2-parameter EOS or 3-parameter EOS?
4. When writing the term (V-b) we subtract b because the molecules occupy volume and when V=b, all the "free volume" is gone. Can you explain the term (P+a/V2) in a similar manner?
5. In the presented example of CO2 at 0.2L and 269K, how does the pressure compare when computed by the ideal gas law vs. the vdW model? (Give both values.)
6. In the presented example of CO2 at 0.0L and 269K, how does the pressure compare when computed by the ideal gas law vs. the vdW model? (Give both values.)

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.

14.04 LLE Using Activities Click here. 80 1

This sample calculation for methanol+benzene shows how to quickly generate the Tx binodal in Excel (uakron, 11min) using the Margules Acid-Base (MAB) model and the Excel iteration feature.(10min, uakron.edu) You generally need to start manually by setting the initial guess for the dilute component in each phase equal to the reciprocal of its infinite dilution activity coefficient. After a couple of iterations, you can set the "guess" cell equal to the "calculated" cell, and let Excel do the rest. Once you get one temperature right, you can usually just drag the fill handle to get the complete Tx diagram in short order. It is best to start at a low temperature to ensure that you detect LLE if it exists.

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
1. Continue the temperature range to 380K with a feed composition of 60mol% methanol. What are the phase compositions and phase amounts in that case? (ANS. 0.299, 0.701, 75%beta-rich).
2. Continue the temperature range to 400K with a feed composition of 45mol% methanol. What are the phase compositions and phase amounts in that case?
3. Generate the binodal for methanol+nPentane for T=[400-460]. At 400K with a feed composition of 60mol% methanol, what are the phase compositions and phase amounts in that case?

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)?
2. What does the acronym "NRTL" stand for?
3. What is the relation between τ12, τ21, and A12 of the M1 model when α12=0?
4. The NRTL model has one more parameter than the Wilson model. Which parameter is it and what is its default value?

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.

10.01 - Introduction to Phase Diagrams Click here. 80 4

Bubble, Dew, Flash Concepts and the Lever Rule (4:01) (msu.edu)

Understanding what is present (known) and not present (unkown) for a given state of a system will help you decide which routine to use. Notation is introduced for liquids, vapor, and overall compositions. Also, the lever rule concept is used throughout the chemical engineering curriculum, but it is important to see how to use compositions for the lever rule.

Comprehension Questions:

1. Which variables are fixed and which do you need to find in each of the following:
a. Bubble temperature
b. Bubble pressure
c. Dew temperature
d. Dew pressure
e. Isothermal flash
f. Adiabatic flash

01.2 Molecular Nature of Temperature, Pressure, and Energy Click here. 76.7273 55

Molecular Nature of Energy and Temperature (msu.edu) (3:34)
This introduction shows the connection with temperature and kinetic energy.  When applying Eqn. 1.1, you must be careful to keep your units straight, as illustrated in this sample calculation of the molecular temperature for xenon (Mw=131). (uakron, 5min).

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.

01.2 Molecular Nature of Temperature, Pressure, and Energy Click here. 76.66670000000001 18

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 PV is related to kinetic energy. This PV relation can be easily understood in terms of an ultrasimplified model of ideal gas pressure. (uakron, 6min). Noting empirically from the ideal gas law that PV=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 4nm3 in size. 

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