# Top-rated ScreenCasts

Text Section Link to original post Rating (out of 100) Number of votes Copy of rated post
07.11 - The molecular basis of equations of state: analytical theories Click here. 100 1

Nature of Molecular Energy - Example Calculation(8min, uakron.edu) Given an estimate for the radial distribution function (RDF) integrate to obtain an estimate of the internal energy. The result provides an alternative to the attractive term of the vdW EOS.

09.04 - Changes in Gibbs Energy with Pressure Click here. 100 1

Gibbs Energy - Nuts to Soup. (learncheme.com, 8min) It is straightforward to start from the definition of Gibbs Energy and derive all the changes in Gibbs energy. These can be graphed for H2O to see how familiar quantities from the steam tables relate to changes in this unfamiliar property.

When you use a spreadsheet like Steam.xlsx(uakron, 15min), interpolation can be greatly expedited. It is recommended that you enable the solver before applying Steam.xls.

Comprehension Questions:
1. Compute H if given T=275 C and P=0.45MPa.
2. Compute H if given T=275 C and V=0.555m3/kg.
3. Which would be more practical for solving a project, double interpolation or steam.xlsx?

Nonideal Mixtures (4:58) (msu.edu)

Raoult's law is an easy way to calculate VLE, but it is inaccurate for most detailed VLE calculations. This screencast provides an overview of the problems, and introduces the concept of an azeotrope. The VLE K-ratio is shown to be less than one or greater than one dependenting on the overall system concentration relative to the azeotrope composition where K=1. The concept of positive and negative deviations is introduced.

Distillation is the primary choice for separations in the petrochemical industry. Because the majority of chemical processing involves separations/purifications, that makes distillation the biggest economic driver in all of chemical production. Therefore, it is very important for chemical engineers to understand how distillation works (21min, uakron.edu) and how VLE plays the major role. This video is a bit long, but it puts into context how phase diagrams and thermodynamic properties relate to very important practical applications. You may find it helpful to reinforce the conceptual video with some sample calculations.(12min) At the end of the video, you should be able to answer the following:

Consider the acetone+ethanol system. Use SCVP (Eqn 2.47) to answer the following.

1. Sketch a Txy diagram for acetone+ethanol at 1 bar with accurate Tsat's. Label completely.
2. Which component pertaining to #1 would have enhanced concentration in the distillate?
3. Accurately sketch the yx diagram pertaining to #1
4. Use Raoult's Law to estimate αLH pertaining to #1.
5. Use your sketch from 3 to estimate Nmin  to go from x1=0.1 to 0.9.
6. Use the Fenske equation to estimate Nmin  with splits of 0.9 and 0.1.

Dew Temperature (7:57) (msu.edu)

The culmination of the activity coefficient method is application of the fitted activity coefficients to extrapolate from limited experiments in a Stage III calculation. The recommended order of study is 1) Bubble Pressure; 2) Bubble Temperature; 3) Dew Pressure; 4) Dew Temperature. Note that an entire Txy diagram can be generated with bubble temperature calculations; no dew calculations are required. However, many applications require dew calculations, so they cannot be avoided. The dew calculations are more complicated than bubble calculations, because the liquid activity coefficients are not known until the unknown liquid mole fractions are found. This screencast describes the procedure and how to implement the method in Matlab or Excel.

Introduction to Phase Behavior (9:37) (msu.edu)
Students tend to be distracted with the algorithms for bubble, dew, and flash, and often miss the important concepts of the relation of the calculations to the phase diagram. This screencast discusses the pure component endpoints, the trends in phase behavior at the bubble and dew conditions, and the qualitative relation between the P-x-y and T-x-y diagrams.

Comprehension Questions:

1. Referring to the Txy diagram on slide 3, estimate T, nature (ie. L,V, V+L, L+L), composition(s), and amount of the phase(s) for points: a, b. d, g.
2. Referring to the Txy diagram on slide 3, suppose we had T = 340K and zA = 0.40. Estimate T, nature (ie. L,V, V+L, L+L), composition(s), and amount of the phase(s) for that point.
3. Which component is more volatile, A or B?

1. Peng-Robinson PVT Properties - Excel (3:30) (msu.edu)

Introduction to PVT calculations using the Peng-Robinson workbook Preos.xlsx. Includes hints on changing the fluid and determining stable roots.

Comprehension Questions:

1. At 180K, what value of pressure gives you the minimum value for Z of methane? Hint: don't call solver.

2. At 30 bar, what value of pressure gives Z=0.95 for methane?

3. Compute the molar volume(s) (cm3/mol) for argon at 100K for each of the following?
(a) 3.000 bars (b) 4.000 bars (c) 3.26903 bars.

SLE using Excel with the M1 model (7min, uakron.edu)

Similar to LLE in Excel, the iteration feature can be used to quickly solve for SLE at multiple temperatures.

Comprehension Questions:
1. Estimate the solubility of naphthalene in benzene at 25C. (a) Use the ideal solution model. (b) Use the MAB model. (ANS. a. 0.306, b. 0.302)
2. Estimate the solubility of biphenyl in nhexane at 25C. (a) Use the ideal solution model. (b) Use the MAB model.
3. Estimate the solubility of phenol in benzene at 25C. (a) Use the ideal solution model. (b) Use the MAB model.