CHEMISTRY COMMUNITY

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306060519 wrote:Happy late Birthday ! I hope you had a nice day.

Thank you.
It was a while ago. :-)

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Hopefully resolved.

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if anyone has the same question:
viewtopic.php?f=140&t=129849&p=548783&hilit=vivek&sid=30570e2fcc7f26350dd66c790e132d89#p548783

-Vivek

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Usually many people drop within the first two weeks. Don't give up hope--keep checking when the quarter starts, go to lecture, and I think you would have a good shot at finding a dropped spot.

-VIvek

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acids and bases

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Contact Achieve support. They are assisting real-time.

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Make sure to read:

Weekly Online Discussion (Chemistry Community)
https://lavelle.chem.ucla.edu/wp-conten ... ussion.pdf

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Click on your username and count how many posts made this quarter as all your posts are listed.

Need minimum 20 questions and 20 answers as stated online.

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This is very strange.
Ask Achieve technical support to contact me.
They also need to explain why a different browser does not work.

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Great!
Well done!

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Another helpful review.
:-)

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Useful review.
:-)

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Popular notes.
:-)

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Hi everyone, I've attached the electrochemistry slides below for anyone who wants to review (also have a minor correction in there):

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Use a different browser.
Achieve support is another option.

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UCLA grade scale or better.

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Students could ask how to do a problem in TA office hours and on Chemistry Community all quarter.

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305961049 wrote:Probably a dumb question but for number 10, why is n=2... I think this could be my sleepy brain, but someone help!

You’re good haha super valid question! n is based on the electrons transferred in our redox. We see that 2e- are transferred in the reduction and oxidation, so n = 2.

- Patrick

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Here is the Zoom recording from today's final review session! Topics covered are Thermodynamics, Kinetics, Chemical Equilibria, and Acids & Bases. Apologies for the first few minutes getting cut off, it was just a brief example/explanation of microstates and introduced the Boltzmann equation as ...

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Hi everyone! Apologies for the delay but an answer key to this week's session can now be found attached here. Again, feel free to email me at shrinidhy02@ucla.edu if you have any questions. Good luck on your final tomorrow, y'all will do great!

-Shrinidhy

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Kinetic Slides (continued)

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I would show the work because it is a free response test and you get points for showing your work.

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For this question, I first wrote the general formula E=Ecell-(0.0542/n) x logQ, then since it was at equilibrium and we know E=0, I wrote Ecell=(0.0592/n) x logK and derived the expression for solving K. Hopefully that helps

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You can, but its just a difference in how the formula is understood. If you do the flip, -1.68, becomes 1.68, and then you do Ecathode + Eanode = -1.18 + (1.68) = 0.5 You could also just not do the flip, only the difference is the formula would be Ecathode - Eanode = -1.18 -(-1.68) = 0.5; which is ...

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I have a question about question 4: Screenshot 2024-03-14 085842.png From my understanding, knowing that all the acids have very large Ka and are strong, we only need to calculate the equilibrium constant of acid dissociation Ka = -log(pKa). But I was just wondering why how the pKa can help rank th...

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Hey guys, see you soon at my review session! Here are the notes:

Acids and Bases review.pdf: (4.76 MiB) Downloaded 97 times

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I just realized I made a small booboo in the answer key -- For the part where you fill in the chart, the equations for the 2nd order reaction are incorrect. Please refer to your equation sheet to figure out which one applies :)

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For the last question, how come the partial pressure of H2 is not taken into consideration for the expression for Q. In other problems I have seen PH2 being used in the Nerst equation as part of the expression for the reaction quotient. This is a great question! The reason we don't account for the ...

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Hi everyone!

I hope y'all are doing well! We will be going over the W10 WS on Electrochemistry Review. I will be posting the answer key after each session. Hope to see you all at the session!

(Here is the link: https://ucla.zoom.us/j/99341875539?pwd= ... RrYm1OQT09)

Best,
Isabella

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The Arrhenius equation was obtained by analyzing data from experiments on the kinetics of chemical reactions.

It is therefore an empirical equation based on experimental data and was not derived.

Hence I did not derive it in class.

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Here is the answer key! Best of luck on your Final!

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hi good luck on the final! here's some practice problems :))

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They are a combination of Q&A with concepts needed to answer questions.

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As promised, here is the answer key! Great job to everyone who came in person today, especially to those who stayed the whole time either standing or sitting on the floor. If you weren't able to make it, definitely check out the answer key and ask if you have any questions. Good luck on the final an...

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Here it is!

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Hey guys! Thank you so much for attending my last step-up session! In preparation for your final, I am posting my completed worksheet as a reply to this post. It includes some questions we didn't get a chance to go over, but feel free to email me if you have any questions. Good luck on Sunday!

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Useful. Thanks

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Useful. Thanks

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The worksheet is done! Yes, it's 16 pages. No, it's not 16 pages of questions. Again, while the questions will cover concepts from all over CHEM 14B, you will need to do additional reviewing to make sure you understand all concepts. I tried putting everything useful onto one document (including clas...

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Hi all,

Here are my lecture notes from Chem 14B. I hope they can be useful as you review for the final!

Feel free to contact me by email, social media, or anything else convenient if you have Chemistry questions as you're studying (:

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Here is the answer key

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Here's the answer key!

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Here is the answer key! Thank you to everyone for coming!

UA Thermo.pdf: (2.81 MiB) Downloaded 80 times

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Yes

Do what I did in the class.
Treat the first step at equilibrium and use it to obtain an expression for the intermediate concentration.

Then substitute out the intermediate concentration in the rate law for the slow step.

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I will make an announcement on this.

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Please read what was already announced on Bruin Learn under the module "Final". "The final reflects the Syllabus. Sections are not weighted more or less. For example, electrochemistry and kinetics are 4 weeks." I have commented on this multiple times (Chemistry Community, Bruin L...

Chem_Mod

Hello everyone! I've attached my worksheet and review sheet which I will go through today. My sessions are on Wednesdays from 7-9 pm in Covel Southbay on the hill (It is located on the third floor in Covel Commons) Due to large number of people attending today's session and not enough room, I decide...

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Hello! The reason you got a slightly different answer is because 10^69 is a very large number and when you input it in the calculator, it rounds it differently. As long as you say 10^69, it is enough and the slight variation doesn't matter.

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Here is the key!

Cheers,
Gabriel

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n is the moles of electrons in the balanced redox reaction.

You can watch my lecture where I discuss this.

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Since they were done the very next day they will be counted.

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Correct. Double time. Double points.
Midterm 1 was 12 questions. Double would be 24 questions.
It will be less than 24 questions.

I keep answering questions on Chemistry Community every day and need more time to work on the final.
If I knew how many questions I would say so.

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Here is the key! Once again, thank you so much everyone for a great quarter. Seeing the same people every week made me incredibly happy :) Wishing everyone luck on the final! You'll all do great! Feel free to reach out if you guys ever need college/premed advice or want to keep in touch! Email is ma...

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Here is the WS I'll go over tomorrow 4-5 on zoom!

UA Thermo.pdf: (277.17 KiB) Downloaded 149 times

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Enzyme kinetics (Michaelis Menten kinetics) is not part of the Syllabus.
Please see my Kinetics outline:

https://lavelle.chem.ucla.edu/wp-conten ... netics.pdf

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Hi everyone, Thank you for the wonderful two quarters that I've spent with you or one if you didn't have Dr. Lavelle for 14A. I hope I was able to make you laugh a little, study more effectively, and most importantly, understand chemistry more. Some of y'all I will see around campus, some of you I w...

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So sorry for the delay! Here you go :)

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Notes for thermo because it’s the hardest unit

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Hey everyone, I wasn't feeling super well last week so I'm covering my week 9 kinetics worksheet this week! My step-ups will be 4-5pm and 5-6pm like normal. I can't believe two quarters have passed so quickly and I'm extremely grateful to everyone who's been able to make it to my sessions. We're alm...

Chem_Mod

Hi everyone! My final/Week 10 review will be hosted tomorrow, March 12, from 9:00AM - 11:00AM in YH 4232. We'll be working through problems and I'll answer any questions that anyone has. No pressure to come in having worked these problems out, we'll go through them together. As always, if you have a...

Chem_Mod

A clarification for today's session: We don't include pure solids when applying Le Chatlier's Principle. In our session today, I said we only worry about aqueous, gas, and solid phases but not liquid. This is incorrect--we only worry about aqueous and gas, but not solids or liquids. Thanks to everyo...

Chem_Mod

Please read what was already announced on Bruin Learn under the module "Final". "The final reflects the Syllabus. Sections are not weighted more or less. For example, electrochemistry and kinetics are 4 weeks." I have commented on this multiple times (Chemistry Community, Bruin L...

Chem_Mod

Your number is correct. 3.3 x 10 6 is approximately 10 6 . Measuring the difference between 3.3 x 10 6 and 1.0 x 10 6 would be extremely hard to do. Very large equilibrium constants are often given without significant figures. The % difference (error) between 3.3 x 10 6 and 1.0 x 10 6 is extremely s...

Chem_Mod

Please read what was already announced on Bruin Learn under the module "Final". "The final reflects the Syllabus. Sections are not weighted more or less. For example, electrochemistry and kinetics are 4 weeks." I have commented on this multiple times and will discuss it again in ...

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Hi, The general concept was relating the differential rate law from the mechanism to the tabulated data. The notation here is to denote that the product of all these constants can be simplified into one constant: k'. It was intended to make it easier to visualize the rate law without three different...

Chem_Mod

Hi everyone,

We're at the home stretch!

My final review will focus exclusively on kinetics.

Here is the worksheet.

See you Saturday! =)

Cheers,
Gabriel

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The different ion concentrations inside the electrode and in the solution create a voltage difference which is measured.

Using the Nernst equation the only unknown is the ion concentration in the solution which is then calculated.

Watch my last lecture on electrochemistry where I discuss this.

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Hey everyone! The CHEM 14B Final is here -- you all are nearly done! For this week's step-up session, I'll be making a complete CHEM 14B review worksheet as many of you have requested. I am still working on it, but expect it to be posted Wednesday night by the latest. Do keep in mind that I will not...

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The question will state, determine the overall rate law from the following proposed mechanism.

The question will give information on which step in the mechanism is the slow step.

I discuss this in class.

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"Vision depends on the protein rhodopsin, which absorbs light in the retina of the eye in a reaction in which one form, metarhodopsin I, is converted to another, metarhodopsin II." In frogs the half-life of this reaction is less temperature dependent which enables frogs to maintain their v...

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Use the one that matches the reaction in the question.

Or given two standard-reduction half-reactions in the question, reverse the one that gives the largest positive voltage to determine/predict the redox reaction.

Rewatch my lecture as I discussed this in detail.

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Definitely a table, but both could occur.

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It is a convention. Also one focuses typically on the product that is formed and its concentration is increasing (positive). If one relates the change in product concentration to the change in reactant concentration, then need to change the sign for reactant rate: R ---> P -d[R]/dt = d[P]/dt Warning...

Chem_Mod

Hi! Here is my worksheet for my final review step up session on Monday at 10AM on Zoom (not 11). I will be covering acid base and equilibrium free response problems. See you soon! *correction* on number 3 of the problems section, [HA] = 0.096M *correction* on number 7 of the problems section, 60% of...

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Well Done

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Hopefully this was resolved.

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When the half reaction does not involve a conducting metal solid.
I will do an example in my Wed review in class.

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Hope you feel better.

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Hope you feel better.

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The UAs are reviewing different topics this week.

I'll be going over equilibrium and acids/bases this week. Let's finish strong.
-Vivek

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Worksheet pdf

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Hi all,

This week my workshop will be focused on covering the rest of kinetics. I'm not running a dedicated general review session, but you're obviously free to bring all your questions on any topics to my sessions, and I'll do my best to answer.

Hope to see you there!

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Hi,

Hopefully, it is still in the De Neve Sycamore room. If not, I'll send an announcement on this thread.

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Here is the key!

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Hi everyone,

Sorry about this but we are in the Magroove room today as someone took our room. I'll be contacting residential life about it.

Here is the zoom link to join for you to see the work: https://ucla.zoom.us/j/97331468794

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Don't mix up rates with rate constants.

At equilibrium: rate forward reaction = rate reverse reaction

With respect to rate constants, the ratio of the rate constants is equal to the equilibrium constant:

k(forward)/k(reverse) = K

Chem_Mod

Great question but Michaelis-Menten enzyme kinetics is not part of the syllabus.
If it is discussed, then students may mistakenly think it is part of the final exam next weekend.

See Kinetics Outline: https://lavelle.chem.ucla.edu/wp-conten ... netics.pdf

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Agreed. Good catch on the sign typo, and thank you. Since we are not using the steady-state approximation I won't update the error file as this could mislead students into thinking that the steady-state approximation is part of the syllabus. See Kinetics Outline: https://lavelle.chem.ucla.edu/wp-con...

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Hey everyone, It's almost finals time so this week's session will be a review session. We will be doing a review worksheet during the session since I covered kinetics last week and I can answer any last-minute questions you have. I am also attaching a comprehensive summary sheet that contains everyt...

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here's the answer key!

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Here is the answer key!

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Definitely not expected to memorize any constants.

I will also give all standard reduction half-reactions.

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The concentration of reactant must decrease with time. Otherwise, the reaction is at equilibrium.

But the rate at which the reactant concentration changes is not dependent on the reactant concentration, hence zero order.
Hope this clarifies.

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Hi everyone!

I hope y'all are doing well! We will be going over the W9 WS on Kinetics. I will be posting the answer key after each session. Hope to see you all at the session!

(Here is the link: https://ucla.zoom.us/j/99341875539?pwd= ... RrYm1OQT09)

Best,
Isabella

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Kinetics Slides

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Kinetics practice!

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Key is posted!

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On changing the initial reactant concentration there is no change in the initial reaction rate.
Then the rate is independent of that reactant (zero order).

I mentioned this in class yesterday.

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