Mass Transfer Topic

I am overwhelmed by the massive information covered in unit operations. Some requires trial and error which takes way too long i.e. in Six-Minutes. What separation processes should I focus on? From previous exam, I've seen very few leaching and extraction problem, mostly distillation and adsorption (gas and packed beds). What about drying, evaporation, humidification, and filtration.

Samzmom08 said:

I am overwhelmed by the massive information covered in unit operations. Some requires trial and error which takes way too long i.e. in Six-Minutes. What separation processes should I focus on? From previous exam, I've seen very few leaching and extraction problem, mostly distillation and adsorption (gas and packed beds). What about drying, evaporation, humidification, and filtration.

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I would stick to the distillation and absorption columns. There are not very many equations for the other, "minor" separations and if you have them handy you should be able to plug and chug in under six minutes. Those you specifically stated can mostly be solved by psychrometry so make sure you know that as well.

Something that would take way to long to calculate is still fair game for qualitative type questions, so as long as there is a genral understanding and good reference that should be enough.

snickerd3 said:

Something that would take way to long to calculate is still fair game for qualitative type questions, so as long as there is a genral understanding and good reference that should be enough.

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I saw some questions on that NCEES sample test regarding strippers that was pretty detailed calculations and it was not a qualitative type question there was a number answer. Whew, it will be an act of God if I pass this lol.

Stick to what's on the NCEES ChE exam topics list. I spent alot of time studying some separation topics that were not on the NCEES list, simply because they were in the ChERM. It was a waste of time.

The last few chapters of CheRM are basically useless. Like what Rudy said, use CheRM to study the topics the NCEES list highlights and you should be fine.

snickerd3 said:

The last few chapters of CheRM are basically useless. Like what Rudy said, use CheRM to study the topics the NCEES list highlights and you should be fine.

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Yea I learned that and basicly cut off my study after phycometrics under the plant design section, there are a bunch of bizare questions on materials of construction which maybe will represent 1 question on the test and that information will likely come out of a random section in perrys anyways. So I figure I will put a few tabs in my perrys and read through pertent sections of perrys just to be a little more familiar with it.

I wonder how many people found Perry's useful during the exam? A co-worker of mine told me that Perry's was useless. I took it with me anyway. I tried to use it for one question in one of the exams (out of the three times I took it), but couldn't find what I needed. Who knows... maybe that's why I didn't pass it with flying colors.

If I may ask does anyone know how to solve question #37 of Nandagopal in the first practice test? It states that fractional volumetric conversion = (Va=1 - Va=0)/Va=0 and it states Va=1 = 3 and Va=0 = 2 where did the values of 3 and 2 come from in the problem statement, there was also a question like this in the NCEES practice test so its not something I want to gloss over. thank you in advance for the help, I am doing what I can to look things up in my reaction text but this question has me stumped.

V xA=1 = 3

This comes from the final number of moles: 2 moles of R + 1 mole of S (right side of reaction; products) = 2 + 1 = 3

V xA=0 = 2

This comes from the initial number of moles: 2 moles of A (left side of the reaction; reactants) = 2

There is also an example of this same type of problem in the Levenspiel book (2nd edition) page 72. It's on questions like these that the appendix is very useful. What reaction text are you using?

rudy said:

V xA=1 = 3This comes from the final number of moles: 2 moles of R + 1 mole of S (right side of reaction; products) = 2 + 1 = 3

V xA=0 = 2

This comes from the initial number of moles: 2 moles of A (left side of the reaction; reactants) = 2

There is also an example of this same type of problem in the Levenspiel book (2nd edition) page 72. It's on questions like these that the appendix is very useful. What reaction text are you using?

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H. Scott Fogler - Elements of Chemical Reaction Engineering third edition part of the prentice hall series. Thank you very much for the answer I will include that in my reference manual for the exam I am finding that Nandagopal has alot of good questions, I probably will be able to do the 6 min solutions before the exam as well so the more problems the better. I have about 6 weekends before the exam and I usually get in a good 2 hr after work as well, my GF is very understanding.

Another question how useful was it to have a set of solved problems in a binder that you solved neatly by hand?

You're welcome rppearso. It was very useful to have problems solved neatly by hand. I only did this for the NCEES practice exam and the two Lindberg exams. I probably referenced them for one or two problems when I re-checked them. But re-writing them neatly helped me remember the way to work them. It was a good confidence builder for me to carry them in.

rudy said:

You're welcome rppearso. It was very useful to have problems solved neatly by hand. I only did this for the NCEES practice exam and the two Lindberg exams. I probably referenced them for one or two problems when I re-checked them. But re-writing them neatly helped me remember the way to work them. It was a good confidence builder for me to carry them in.

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I will definitly have to do that then I have a stack of E2 paper with them solved quickly so I will go back and redue it as soon as I finish the Nandagopal book, the lindberg question book was huge and included complex topics so I am not sure if I want to include that not to mention I did about 2 years worth of problems so it would be impossible for me to reference them in a useful manner in the exam.

As of now I am planning on bringing the following into the exam maybe you could correct me if you think I need more or less:

1. Solved problems from Nandagopal and the NCEES practice exam per your recommendation

2. Quick reference (with significant additions in pencil, chopped and spiral bound)

3. Scanned all the reference section out of the hard back Lindberg book and had it spiral bound so I did not have to flip the large hard back book around in the exam

4. unit conversions hand book (chopped and spiral bound)

5. tabed crane manual for much quicker calculation of hydralic problems with less unit conversions

6. possibly a tabed perrys (although im not sure how useful it would be, I guess if I have one question left and have bought myself enough time to dig through it the more points the better right)

I want to avoid bringing in a gigantic stack of all sorts of stuff that will clutter up my work area but at the same time dont want to be short a reference.

This forum is awesome I wish I had found this sooner, I feel like a lone ranger at work taking the chemical PE exam and I work at BP, there are only 50 practicing chemE's in my state and only 100 total (I figured out who was retired and just maintaining there licence because I sent letters to all of them when I was looking for a job to start my 4 years).

Another question regarding question 58, how can the total moles started with be less than the total mols at equlibrium. The problem solution states that the 43% conversion of CO2 is to CO and not CO and O2, this is a bit confusing.

rppearso said:

Another question regarding question 58, how can the total moles started with be less than the total mols at equlibrium. The problem solution states that the 43% conversion of CO2 is to CO and not CO and O2, this is a bit confusing.

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I am also struggling with partial pressures on #79, in the solutions they just state the vapor pressure of each component and im not sure how they got it. Sorry to inundate with questions but I dont really have anyone to ping things off of.

rppearso said:

Another question regarding question 58, how can the total moles started with be less than the total mols at equlibrium. The problem solution states that the 43% conversion of CO2 is to CO and not CO and O2, this is a bit confusing.

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The moles started (25) is less than the total moles of equillibrium (30) is possible because it is the number of moles, not the mass. If there was no conversion to take into consideration, then 25 moles of CO would convert to 25 moles of CO and 12.5 moles of O2 (25 + 12.5 = 37.5 moles). CO2 ==> CO + (0.5) O2

The 43% conversion of CO2 to CO, allows the calculation of number of CO moles reacted:

Moles of CO2 reacted = (0.474)(25) = 11.85

Moles of CO = 11.85 (from the balanced reaction: 1 mole CO2 = 1 mole CO)

Moles of O2 = (0.5)(11.85) = 5.93 (from the balanced reaction: 1 mole CO2 = 0.5 mole O2)

Having 43% conversion of CO2 to both CO and O2 complicates the problem.

rppearso said:

I am also struggling with partial pressures on #79, in the solutions they just state the vapor pressure of each component and im not sure how they got it. Sorry to inundate with questions but I dont really have anyone to ping things off of.

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I think these were gotten from tables in Perry's, since they are vapor pressures of each component at a specific temperature (70 F). It's been a while, so I might be wrong as to the source of the values.

rudy said:

I think these were gotten from tables in Perry's, since they are vapor pressures of each component at a specific temperature (70 F). It's been a while, so I might be wrong as to the source of the values.

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I think you are correct after thinking about it, I hope I do not have to dig up stuff in perrys to answer a quantitative questions on the actual exam. Anyways what did you think of my list of materials I plan on bringing into the exam? I am going to move on to practice exam 2 this weekend, I am finding I am having to look to the solutions way more often than I should on alot of these problems, as I do that I make notes of equations I am missing in my references and such but I would think as I do more and more problems I should have to look to the solutions less and less, I hope after having done all the questions out of the problem book that accompanies the hard back reference manual and both practice exams and the NCEES practice exam that the 6 min solutions should be doable without having to turn to the solutions for very many, if I get through the 6 min solutions book and still have to look at solutions then at that point all I can do is prepare an extensive set of neatly worked problems along with the rest of my list above and cross my fingers and pray lol.

rppearso said:

Anyways what did you think of my list of materials I plan on bringing into the exam?

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Looking good. Bring all the books you are used to using. I put the books I used the most (i.e. ChERM, Crane, etc) on the table. The books I used the least or the ones I did not have enough time to go thru (Das PE Review, Perry's, etc), I left in my suitcase on the floor. I think I had left my Unit Operations in the suitcase, but it came in handy at least once.

The way I got used to the books, was by mimicking exam conditions about four to six weeks before the exam on Saturdays. I had gone thru all of the practice exams, so I made up my own. I picked a few from each chapter of Das to get a good variety and worked them as if they were the real test -- using my references and not allowing any extra time. This helped build stamina; and tab my references and add to my ChE notes after the "test".

You're right the more problems you do, the less you'll be looking at the solutions.

rudy said:

Looking good. Bring all the books you are used to using. I put the books I used the most (i.e. ChERM, Crane, etc) on the table. The books I used the least or the ones I did not have enough time to go thru (Das PE Review, Perry's, etc), I left in my suitcase on the floor. I think I had left my Unit Operations in the suitcase, but it came in handy at least once.
The way I got used to the books, was by mimicking exam conditions about four to six weeks before the exam on Saturdays. I had gone thru all of the practice exams, so I made up my own. I picked a few from each chapter of Das to get a good variety and worked them as if they were the real test -- using my references and not allowing any extra time. This helped build stamina; and tab my references and add to my ChE notes after the "test".

You're right the more problems you do, the less you'll be looking at the solutions.

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What is Das I dont believe I have that book, what is the ISBN? I still have about 2 months and while I am waiting for it in the mail I have the 6 min solutions 100 questions to work through, if I dont have Das by now do you think it would be futile to order it now and maybe I should only order it if I fail this one?