Multiple Unit Material Balance: Degree of Freedom Analysis

[@mkb3195]

This video is amazing, I am in my first year of ChemE degree and your video is the reason I have not given up

[@hassanasif6675]

+LearnChemE Hats off.The way you explained such a bizarre topic...#Wow

[@albertoaguilar9773]

One of the best explanations I've seen so far. Keep it up buddy.

[@nhaz652]

PERFECT EXPLAINATION. Now i can see it clearly.

[@poonambagade3715]

Very well explained. Thank you very much. its very helpful for my studies.

[@rubixcubesolve]

T AROUND 5:10 YOU say that we have an overall balance, and methanol balance, and an h20 balance. Why did you say that we can only write 2 of the 3 down??

[@LearnChemE]

Thank you for your question. Of the three possible balances, only two of them are independent. For example, if you added the methanol balance and the H2O balance, you would get the overall balance. So the third one would not be helpful. Thus, you have to choose only two.

[@rubixcubesolve]

makes sense! thank you so much

[@AmlakuKassew]

This video is amazing

[@92muztafa92]

I love you #nohomo, how simple and easy you explained it

[@ABHISHEKGUPTA-bl1pb]

Superb explanation. Kudos

[@سالمالشمري-ت7ب]

How did you find the rest of the percentages and the number of moles in the products n4,n5,y5m 11:00 please? I tried to find them but I could not!

[@LearnChemE]

Thanks for the question. From the problem statement, we know that n4 has the same flowrate at the top stream of unit 1, so it is 40 mol. We can then solve for stream n5 by doing an overall balance on unit 2 (n4 + n5 = 70, n5 = 30). Then a component balance around unit 2 will give us y5m (M: 0.37*70 = 0.5*40 + y5m*30, y5m = 0.1967 or 0.20) The key was going back to the problem statement to find that the top streams have equal flows. I hope that helps!

[@سالمالشمري-ت7ب]

@@LearnChemE Thank you very much

[@javedfaizal5473]

perfectly explained! thank you so much

[@abdulmusawwir8603]

why you haven't included n1 and y3M in the overall unknowns?

[@LearnChemE]

+abdul musawir When doing the overall balance, you do not need to know anything about the internal streams. You are only concerned with what is going in and out of your "system". Please look at the video at 4:00 to see the line drawn around the system. The streams that cross that are the ones that we need to solve for in this case.

[@milanapranic6958]

This is brilliant.

[@Syvmana]

What are the two relationships in 7:17 ?

[@LearnChemE]

+Syvmana The relationships around the mixing point are two material balances, either two species balances or the overall balance and one of the species balances.

[@alviranooratqiya4277]

thank you so much, very well explained👍👍

[@florentinosanchez3969]

Best video ever!!!

[@Haneen-wg1sn]

You can give me the sources about balancing the material. I really need it❤️❤️

[@wasifnayef3847]

I have a doubt.First u have calculated DOF of overall process unit. In this case u supposed to take n2 a variable. Well. Again in unit 1 u took n2 as a variable. So my question is that is it right to consider a variable in more than one process unit while finding out DOF value.I taught that if a variable once considered (used) in finding a DOF value then it would not to be used in finding the later DOF values.I m eagerly waiting for the ans.

[@LearnChemE]

Good question. The DOF calculation for the overall process unit is separate from the DOF calculation around Unit 1. You completely start over, so, no, it doesn't matter that you are using the same variable for those 2 calculations.

[@nhaz652]

Hello..thank you for this video. Just to check on my understanding, at the start, when both feed and aqueous methanol streams enters the #Unit 1, it is considered mixed and we cannot assume the n1 to be 100moles, am i right?

[@LearnChemE]

Yes, you are correct. You can see that one feed stream is 100 moles and the other is 10 moles, so you know that n1 is 110 moles.

[@drdayud]

شكرا جزيلا، thanks alot

[@snowmanapocalypse497]

Thank you thank you thank you I love you I love you

[@charlieni5457]

I can understand the material balance (n2=n4) for the analysis of overall. But why don't you include for the rest of analysis ?

[@LearnChemE]

Charlie Ni When calculating the DOF around Unit 1, n4 is not one of the unknowns, so n2=n4 is not a relevant equation. Similarly, for Unit 2, n2 is not one of the unknowns. Lastly, the mixing point has neither n2 or n4.

[@SnenhlanhlaZinhlekhumalo]

why we didint include that 70mol when we were doing overall balance

[@brettgillespie7492]

Yes! I understood this

[@ShoaibChaudhary591]

Is this problem is without chemical reaction ?

[@dianendepow7311]

why are n1, y1 and y3 not unknowns?

[@xJoelSingh]

I assume you're referring to the total process, they are not unknowns because you are just looking at the streams that go in or out of the process. The ones you mentioned are inside the process (they dont enter or exit the box in the picture) so they are not taken into account.

[@AidanBadillo]

⁠​⁠@@xJoelSingh I understand that y3 is omitted from the overall process because it is not leaving the entire process. How does n1 and y1 not enter the entire box in the picture?

[@javedfaizal5473]

@@AidanBadillo at 4:00 notice that n1 and y1 are already inside the box(the system), not entering it

[@RaunakPrajapati]

very helpful

[@mjeed1008]

how n2=n4 is it stated in the question ?

[@LearnChemE]

Yes, it is stated in the question.

[@Animelover-np8dr]

anyone have a question tell me it because the video is 3 y ago he is not replying at this time

[@muhleujehovahmabuza2482]

Why didn't he include water as one of the unknowns(%wt)

[@aayushsharma8170]

I had the same doubt, but if you read the question, it says that it is added with ' aqueous methanol stream ' so we do not have to write water separately as we have dissolved product :) @@muhleujehovahmabuza2482

[@seriousearth2211]

Tnx a lot

[@nigelstanford4]

Dumb question...When doing the Degrees of freedom, why is it only (unknowns - Relationships)...What happen to species?

[@LearnChemE]

+Tyrone Biggums Not a dumb question, Tyrone. In this case, the narrator is lumping the species balances in with the relationships. If you listen at 5:00, he explains that he is doing this. This is a matter of loose definitions. Thanks for asking.

[@nigelstanford4]

+LearnChemE oh OK thanks

[@collectrawr]

Helpful but these problems are very specific. Try without knowing the % recovered by the m6 stream. Anyone can rearrange and solve for that ;_;