Problem 8 on PS7

There is a typo in that some of the distributions read P(x) when it should be P(z).
Cheers,
MSS

No more Monday make-up lectures

Dear class,

We will not need to hold any more make-up lectures, so Monday we will only meet at the regular time (2-3pm) from hereon out.

Cheers,
MSS

Thought problems for phase equilibrium

Class,

There is a typo in problem 2 for these thought problems. It should read f/P instead of f.

Cheers,
Scott

PS4

Hi class,

For PS4, question number 6, you can also assume that in analogy with the usual fundamental equation, the quantities Cv = (dE/dT)_L and Cp = (dH/dT)_tau are both positive. Similarly, the equivalent of the compressibility (dL/dtau)_T is always positive.

Cheers,
MSS

Final grades

Dear class,

We have finished grading the final and your course grades have been computed. I will endeavor to return these to you at the start of ChE110B. Alternatively, you may stop by my office if you do not get yours back in class next week.

The statistics for the final are:

• average - 61% (62% with bonus from problem session)
• standard deviation - 13% (13% with bonus)
• maximum score - 84% (87% with bonus)

The statistics for the course grade are (with bonus):

• average - 70%
• standard deviation - 10%
• maximum score - 90.7%

The letter grade distributions are as follows:

• A - 27%
• B - 37%
• C - 23%
• D - 8%
• F - 5%

A detailed plot of these distributions can be found on the course webpage.

I enjoyed teaching you all this quarter and wish you the best of success in your future endeavors!

Cheers,
MSS

Study break

Here's an interesting little mathematics / statistical analysis of the NCAA tournament that you may find to be a nice reprieve from your finals studying:

http://fivethirtyeight.blogs.nytimes.com/2011/03/15/when-15th-is-better-than-8th-the-math-shows-the-bracket-is-backward/?hp

These authors show that lower-ranked seeds actually have a higher probability of making it to the sweet sixteen, elite eight, and final four than mid-ranked teams. It's a problem ripe for population balances and rate equations, in truth not really all that different from mass balances and chemical kinetics.

Go Gauchos!

MSS

Office hours tomorrow

Hi class,

Just a small update to my office hours tomorrow. In the afternoon I will be available 4-5:30pm, not 3:30-5:30 as originally indicated.

Cheers,
MSS

Common mistakes on HW9

Dear class,

If you would like your HW9 back, you can retrieve it at the review session tonight or see me in my office tomorrow. Here are a few common mistakes we noticed in grading it:

Problem 49:

Some students did not realize that entropy increases for the nonideal compressor case. The corresponding curve in the Mollier diagram should start at the same place as the ideal case, but then move both up and over to the right, in the direction of increasing entropy. The endpoint will not be the same, although it will intersect the same isobar.

Problem 50:

Some students calculated for the turbine:

W_real = W_isentropic / efficiency
This is the right expression for a pump or compressor, but for a turbine it should instead be:
W_real = W_isentropic * efficiency

Cheers,
MSS

HW9

Hi class,

Please do attach the Mollier diagram that you work in problem 49 to your solutions. If you would like another copy, you can print one out from the online pdf of the homework assignment.

Cheers,
MSS

Final and review session

Dear class,

The final will be Wednesday, March 16, from 12-3pm. It will be open book and one page of notes, similar to the midterm. You should bring a calculator, your book, writing utensils, and your notes page. If you would like to use the first page of the fundamentals handout, and write your additional equations on the back, that would be fine as well -- but in total you should only have one page of notes to bring. The format of the final will be very similar to the midterm, but longer in proportion with the three hour time block.

I will hold an open question-and-answer review session on Monday, March 14 from 6-8pm in Engineering II 1519. Feel free to stop by whenever is convenient during that time to ask questions.

I will also be available to chat during office hours on Tuesday, March 15, from 10am-12pm and from 3:30-5:30pm. My office is Engineering II 3321.

In addition, I will be handing out grade statistics sheets for each student on Friday at the end of class so that you will be able to see how you are doing in the course going into the final.

Cheers,
MSS

Common mistakes on HW6 and HW8

Dear class,

We noticed that there were a number of mistakes on HW6 and 8 involving unit conversions. It is essential that you carry units throughout all of your calculations so that can keep tabs on conversion issues. To avoid a lot of writing, you can keep your equations in analytical form until the final step when you plug in actual values of variables.

Cheers,
MSS

Common mistakes on HW7

Hi class,

Here are some common mistakes that were made on HW7. Please check to see if you made these so as to avoid them in the future.

Problem 32: "well-insulated" implies "adiabatic" - which means Q = 0, not necessarily that delta(T) = 0 (although with an ideal gas in a process that also does no work, delta(T) will equal zero).

Problem 33: need to use absolute temperatures with the efficiency, Qc, and Qh equations.

Problem 34: need to use consistent units with the Q=n*cp*delta(T) equation

Problem 38: constants in table c.1 have units (e.g. B has units of 1/Kelvin and C has units of 1/Kelvin^2); basically another reminder to take care with units and make sure that they match up.

Cheers,
MSS

HW8, problem 42

A slight correction to the problem statement:

In part (b), please calculate the entropy change for the world, i.e., that due to both the system and environment entropy change. The point is to show you that supercooled water freezes, the entropy of the world increases and thus this process does not violate the second law, even though "disorder" may seem to be decreasing.

Cheers,
MSS

Some Notes on Homework #6

Problem 28

When calculating the percent error, compare your calculated enthalpy at 25 °C to the tabulated value at 0 °C (1189.5 J/g). Please ignore the fact that this tabulated value is not at the same temperature as your results. You do not need to rescale the tabulated value to 25 °C.

Problem 31-b

For this problem, assume that no phase changes occur - all components remain gases over all temperatures. Also assume that the heat capacity coefficients given in Appendix C.1 are valid over all temperatures. There is a typo in the problem, so don't worry if your answer seems off, just approach the problem the same way you've learned in class.

Monday morning office hours cancelled

I have a conflicting appointment tomorrow and won't be able to keep my office hour Monday morning. If you have questions on the homework, please email me, stop by my office (Eng. II, room 3218), or come to Anthony, Kate, or Prof. Shell's office hours. I apologize for any inconvenience.

Brandon

Review sessions

Dear class,

Just a quick reminder that I will hold review sessions Wed and Thursday evenings from 5:30-6:30pm in Engineering II 1519.

Also, I have extended the deadline for HW5 to Wednesday, Feb 9.

Cheers,
MSS

Midterm exam

Dear class-

To summarize what we discussed today in class, the midterm exam will be on Friday, February 4th in class. You will have approximately one hour to work the exam, which will cover Chapters 1-3 in the book. Bring a pencil and calculator. The exam will be open book, but closed notes. HOWEVER, you may bring one 8.5 x 11" page of handwritten notes, front and back. This should give you the opportunity to organize the course equations for quick reference during the exam.

Also, note that HW5 is not due until Monday, February 7.

Cheers,
MSS

Lost calculator

Did anyone leave a calculator in class today? One was turned in to me. Please contact me if you believe it is yours, and let me know what type of calculator it is.

Cheers,
MSS

Office hours update and HW2 solutions

Dear class,

The office hour time on Mondays that was 5-6pm has been moved to 6-7pm because of a room schedule conflict.

Also, solutions to HW2 can be found on the course webpage.

Cheers,
MSS

Office hours

Dear ChE110a,

We have secured locations for the office hours for this course, and note that there are different locations depending on the day:

TA office hours
Monday 10:30-11:30am, Engineering II 3301
Monday 5:00-6:00pm, Engineering II 3301
Tuesday 12:20-2:20pm, Engineering II 1519

My office hours
Thursday 11am-12pm, Engineering II 3321 (my office)
Friday 2-3pm, Engineering II 3321 (my office)

Office hours will begin next week. If you need to meet with someone this week, please email one of the TAs as I will be in travel most of the week.

Cheers,
MSS