CHEMISTRY COMMUNITY

Chem_Mod

Apologies for the delay! Here is the answer key for the worksheet.

If you have any questions, feel free to drop them below on this thread specifically :)

Chem_Mod

answers

Chem_Mod

Here's the worksheet and download this appendix pdf

https://docs.google.com/document/d/13qn ... sp=sharing

https://drive.google.com/file/d/1mftSVg ... sp=sharing

Chem_Mod

here are the annotated pdfs from today's session! thank you for bearing with me today

good luck on the midterm you guys!! :D

Chem_Mod

Hi everyone! The answer key for this worksheet is attached here. Again, let me know if you have any questions or if you need anything!

-Shrinidhy

Chem_Mod

see you guys soon:)

marg

Chem_Mod

Hey everyone! Sorry for the last-minute post but today's step-up will be a two hour block, I'm going to spend the first hour reviewing Gibb's free energy and the second hour doing midterm review. I'll post the worksheets in a little bit!

marg

Chem_Mod

When solving for the enthalpy, entropy, or Gibbs free energy of a reaction, it is for the balanced chemical reaction. E.g., 2R ---> 3P When solving for the enthalpy, entropy, or Gibbs free energy per mole of a specific compound then one needs to divide by the moles to obtain per mole. Using the abov...

Chem_Mod

First need to determine moles of HCl and moles Zn to determine which is the limiting reactant. Since Zn is the limiting reactant, it will determine moles of product (which is 0.130 mole). The enthalpies of formation would be given (see tables in textbook). Use enthalpies of formation to determine re...

Chem_Mod

The enthalpies of formation would be given in a test.

Chem_Mod

First need to determine moles of HCl and moles Zn to determine which is the limiting reactant. Since Zn is the limiting reactant, it will determine moles of product (which is 0.130 mole). The enthalpies of formation would be given (see tables in textbook). Use enthalpies of formation to determine re...

Chem_Mod

Here is the updated worksheet. This version includes the tables that we will need to use to solve these questions.

Chem_Mod

Hi Isabella! Could you please post the answer key? Also, for #3 it’s asking to calculate the enthalpy change for C graphite, but there’s no equation given. How do I determine what the equation is? Hi Natalie, I am very sorry that I forgot to put the target equation in the worksheet at the beginning...

Chem_Mod

Please see the answer key attached

Chem_Mod

Here's the answer key!

Chem_Mod

Hi everyone,

Best of luck for the midterm this week! :-)

If you get bored afterwards and need something to do, here is the worksheet for this weekend.

See you then!

Remember to take care of yourselves as well as we near the end of the quarter. <3

Cheers,
Gabriel

Chem_Mod

There is no 4L section.

Chem_Mod

The enthalpies of formation are given in the back of the book (Appendix).

Chem_Mod

See the step-by-step answer in the solutions manual.

Chem_Mod

Using bond enthalpies to calculate the reaction enthalpy is part of midterm 2.

Chem_Mod

Significant figures are more important in lab courses.

We are not focused on them.

Chem_Mod

Hope this was helpful.

Chem_Mod

Reviewing the assigned problems in the syllabus is excellent preparation.

Chem_Mod

Students need to know how to use these Constants and Equations:

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

Chem_Mod

Use these: Outline 3: Thermochemistry and 1st Law Thermodynamics https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14B/Chem14B_Outline3_Thermochemistry.pdf Outline 4: Thermodynamics: 2nd Law, 3rd Law, etc. https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14B/Chem14B_Outline4...

Chem_Mod

Use these: Outline 3: Thermochemistry and 1st Law Thermodynamics https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14B/Chem14B_Outline3_Thermochemistry.pdf Outline 4: Thermodynamics: 2nd Law, 3rd Law, etc. https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14B/Chem14B_Outline4...

Chem_Mod

I will cover this in detail in class.

Reminder that Electrochemistry is not covered in Midterm 2.

Chem_Mod

Weeks 3, 4, 5, 6 slides

Chem_Mod

Alice Feng 1H wrote:
Chem_Mod wrote:Here is the worksheet: https://docs.google.com/document/d/1ERii7V53IavAqoJRnsQmVu0vgiXLTF1U-Bc223_cFV0/edit?usp=drivesdk

where can we find the key? thanks!

Hi Alice,

Here is the key: https://drive.google.com/file/d/1qsXHsr ... p=drivesdk

Chem_Mod

Both 490 J and 4.90*10^2 J are correct. Here, the solutions manual uses scientific notation to report the answer with the appropriate significant figures, but in this class we do not need to worry about sig figs!

Chem_Mod

Following up on my previous answer.

When I cover a biological or environment example in class that is when students should know the biological details, etc.

Otherwise, all the details will be given in the question.

Chem_Mod

Hi Nicole,

For #18, it is in kJ/mol because it is per mole of reaction. So, it may have been more accurate to write kJ/mol_rxn.

For #13, I can see the confusion. You're right, it would be more accurate not to include the per mole element and only include the energy unit.

Chem_Mod

Answer Key is posted.

Thanks for all the emojis today! Remember midterm 2 + you ---> good score is a spontaneous reaction.
-Vivek

Chem_Mod

Here is the worksheet: https://docs.google.com/document/d/1ERii7V53IavAqoJRnsQmVu0vgiXLTF1U-Bc223_cFV0/edit?usp=drivesdk

Chem_Mod

Hi everyone! So sorry about this, but my power went out an hour ago and I now have no Wifi. This unfortunately means that I will have to cancel my 1pm workshop session today. I will still post my worksheet and key as usual. I am so sorry for any inconvenience this may cause, and that you so much for...

Chem_Mod

For question 5, I was under the impression that in a combustion reaction water vapor was formed (water in the gaseous state rather than a liquid state). Wouldn't the answer for work being positive not make sense? We are calculating the work of the system so should it not be negative since the syste...

Chem_Mod

Hi all,

Here is my workshop for Week 7. We will be going over the last bits of thermo, focusing on entropy and Gibb's free energy.

Chem_Mod

Students need to be able to apply the same concepts to examples in biology, industry, the environment, etc., but do not need to memorize specific details about them.

The given information will enable answering the question using concepts and equations covered in class.

Chem_Mod

See the equation sheet at my class website for equations that may be needed.

Chem_Mod

Chem_Mod

This comes up in section 4F of the textbook, specifically problem 4F.7: Where did we learn that the Cp of an ideal monatomic gas = 5/2R? Are we expected to memorize this for our midterm? I sent class email on this topic. Are you receiving and reading my email? From my class message: "FOR GASES...

Chem_Mod

Attached is my midterm 2 review for my step up session 2/19 Monday at 10AM on Zoom. It is a little short so I can take extra questions at the end or along the way!

Chem_Mod

Hi. For 1A and B, please make sure you completed the unit conversions properly and are using a lot of parentheses in your calculations. If you are still having trouble, we can go over it at the end of my session tomorrow 2/19. Please join for the whole session, as I sometimes finish early and take q...

Chem_Mod

Hi,

It is because in this instance, the crystal of BrCl is "perfectly ordered." Thus, only 1 possible state may exist to satisfy this condition.

If it were imperfectly ordered, there may exist 2 states.

Hope this helps! :-)

Chem_Mod

TNT was given because it is not in the tables in the textbook which give the values for most common compounds.

As I stated in class constants will be given.

Unless one was given all the other information that then enables calculating a specific enthalpy of formation.

Chem_Mod

Delta G = Delta H - T Delta S When, Delta S > 0 then -T Delta S < 0 favors spontaneity (Delta G negative). Higher T favors spontaneity. Delta S < 0 then -T Delta S > 0 then does not favor spontaneity. Higher T does not favor spontaneity. Delta H > 0 then does not favor spontaneity Delta H < 0 then d...

Chem_Mod

Area x Distance = AD Any area that moves through a distance D has moved through a volume which is the volume change (delta V). A force is a pressure acting over an area. F = PA Therefore, w = FD = PA D = P AD = P delta V With respect to the system: w sys = - P ex delta V sys I went through this in d...

Chem_Mod

The one I discussed in class is the important role water plays as a solvent, especially for acids and bases in aqueous solutions and biological systems. The important biological functional groups -COOH and -NH 2 act as acids and bases respectively under aqueous conditions. In class I drew the Lewis ...

Chem_Mod

depends on what the units are for. Different variables will have different units, kJ or J. The specific heat capacity of water is 4.184 J/g *K right? Or would you prefer .0041874 kJ/g * K? The J vs kJ part is given really just for whatever number is more convenient; you can convert no matter what th...

Chem_Mod

See you on monday at 2 pm, but this time on zoom. This is the second time my session day has been on a holiday... maybe if I have more sessions we would get more holidays? here's the link: https://ucla.zoom.us/j/94689004078?pwd=YzUzc2RxTkEyVitvaDdlQnpKbnNDZz09 I don't know whether to be happy if you...

Chem_Mod

Hi Vivek, I had a question on number 4 part a. How come the work done on the gas was negative and the work done by the gas is positive? I thought it was always the opposite (work is negative if work is done by gas and work is positive if work is done on the system). Would you please walk me though ...

Chem_Mod

For question 4 c/d how do we know its isolate? Also isn’t the entropy of the universe only 0 if the reaction in question is at equilibrium? Thank you! hi Olivia, The problem only mentioned the gas, isothermally expanding, meaning that work was the only reason for change in entropy here. There's not...

Chem_Mod

Phase changes as discussed in class.
Temperature is constant during a phase change.

Rewatch my lectures.

Chem_Mod

Here is the answer key. Best of luck on your midterm!

Chem_Mod

Hi, In terms of missing information, the little degree symbol at the top of enthalpy (H) is a little hint that the reaction is taking place at 25 C. Thus, you have all the information you need. The only thing is that it is implied you are at 25 C, which is indicated by the degree symbol to denote st...

Chem_Mod

Hi Ilia,

Iodine does not exist as individual gaseous iodine atoms at standard state. Thus, using Reaction 2 would be incorrect.

For Reaction 3, you could consider that as well since sublimation is going from a solid to a gas.

Chem_Mod

Hi y'all,

Thanks for bearing with me today! I wasn't feeling well when I woke up this morning, so thank you for your participation. <3

Here is the key as promised.

Cheers,
Gabriel

Chem_Mod

Hi Vyas, I can see your point. I suppose the purpose of the question was to show that if +1368 J was inputted into the system, -1368 J must have bee removed from the surroundings. From here, assuming the temperature remains constant, then you could have divided which is why the overall value is nega...

Chem_Mod

Always constant volume.

Unless it explodes. :-(
As I commented/joked in class.

Chem_Mod

A redox reaction is spontaneous when the cell potential is positive or the Gibbs free energy is negative.

I will discuss this in class next week.

It is currently a holiday long weekend, but not for me. :-)

Chem_Mod

Because solids and liquids have very small volume changes on heating, and therefore no work of expansion when heating under constant pressure conditions.

I mentioned this in my lectures.

Chem_Mod

key and video are attached, I'm so sorry for the delay! I tried posted the video directly as well as including a link to Google drive, hopefully one of the two options work

good luck with studyinggggg

marg

https://drive.google.com/file/d/15zxPN5 ... sp=sharing

Chem_Mod

here is the key!

please ignore #4, it's an outdated question and I don't think it's one of the syllabus problems either so I didn't cover it in my sessions

also 2a) is supposed to be ln(1) not ln(0)

Chem_Mod

Hey Vivek, I had a question about #5. For delta S #3, shouldn't the numbers within the natural log be flipped? That would make the overall answer negative, so the final answer would be smaller than what you have. Please let me know where I went wrong. Thank you! Hey Rithwik, Remember we are solving...

Chem_Mod

Week 6 Second and Third Laws of Thermochemistry (Continued)

Chem_Mod

Hi everyone!

I hope y'all are doing well! We will be going over the W6 WS on MT2 Review. I will be posting the answer key and the review notes 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

Chem_Mod

Interpret it the same way I did in Wednesday's class this week.
I discussed it in detail in class.

Summary:

The minimum is Delta G = 0.

A spontaneous process is Delta G negative, and it releases energy that is available to do work.

Chem_Mod

Hey everyone, I’m so sorry but I have to cancel my session tomorrow because I have a field trip at the same time. Here are the notes about Gibbs free energy. Please don’t hesitate to reach out if any of it doesn’t make sense.

Week 6 step up.pdf: (3.55 MiB) Downloaded 248 times

Chem_Mod

Hey everyone! Next week's session will be midterm review session. The review session will be from 10am-12pm in Young Hall 4232. This midterm will be thermodynamics heavy so that's what I will be covering in my sessions. The summary sheet for this week is just a compilation of the summaries from week...

Chem_Mod

Here's the answer key!

Chem_Mod

Good luck on your midterm next week! Here's some extra questions to review the last bit of thermo

Chem_Mod

Hey Everyone!

Here is the worksheet for this week.

YH 4232 10-11 and 11-12 pm as usual :)

~ Patrick

Chem_Mod

How you solve it depends on the given information.

Chem_Mod

Watch my lecture. I did the derivation in class.

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).

Chem_Mod

I will discuss this in detail in tomorrow's class.

Chem_Mod

Hi everyone,

I am extremely ill right now and I am unable to give my usual in person session.

I've attached my slides and worksheet. I deeply apologize for anyone who wanted in person,!

Best,
Jaden

Chem_Mod

hey everyone, I'm starting thermodynamics this week!

I'll also post the week 5 thermochem recording Thursday at the latest, sorry for the delay!

marg

Chem_Mod

Here are the answers! I will actually be available on my zoom tomorrow from 8-9:45am before my classes and midterm if you want to join and ask any questions or have me go through the worksheet!
https://ucla.zoom.us/my/kaetheszoom

UA Week 6 (3)-1.pdf: (2.77 MiB) Downloaded 244 times

Chem_Mod

Hey guys here is the week 6 worksheet I made. I unfortunately cannot host my session tomorrow due to my midterm, but I will post the answer key! Please email me if anything does not make sense! kathezappacosta@gmail.com

UA Week 6 (2)-1.pdf: (276.02 KiB) Downloaded 233 times

Chem_Mod

Hey everyone, This week we will be finishing off thermodynamics with Gibbs Free Energy. As always, my sessions will be on Wednesday from 10-12 in Young Hall 4232. Next week, I will be doing midterm review on Wednesday morning going over content from week 3 til week 6 (basically all of thermo). Email...

Chem_Mod

Hi everyone, Happy Week 6! To prepare for your upcoming midterm, I have created a midterm review worksheet. I will try something different this week. Based on feedback, I will do about the first half of the worksheet on Saturday and the second half of the worksheet on Sunday. Please attempt the work...

Chem_Mod

Hi everyone! Attached are both the review sheet and the worksheet for this week's session. No pressure to come in having either done, we'll go through both during the session. As a reminder, my session is today, Tuesday, February 13th, from 9:00am - 11:00am in Young Hall 4232. Feel free to email me ...

Chem_Mod

the enthalpy of reaction for the products would be starting from their elemental states, right? In an equation we may be forming the products from reactants other than what is found in nature. For example. for C(s) + O2 (g) ----> CO2 (g), you wouldn't have to account for the enthalpy of formation of...

Chem_Mod

I'd say in chemistry, if you can think how it as how many possible combinations can you have? So for CH3Cl, how many possible ways can you draw the lewis structure? W = 4 like your TA probably did, since Cl can be on the top, right, left, or bottom of C. Then you can think about if I have X amount o...

Chem_Mod

I want to emphasize that the variables have a delta in front of them, so the equation is (change in gibbs free energy) =(change in enthalpy) - T x (change in entropy). Gibbs free energy means, will this reaction happen by itself in these conditions? Is the process favorable/spontaneous, meaning I do...

Chem_Mod

copy and pasted my answer from here: https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=76&t=120947&p=525360&hilit=vivek&sid=cdf3619cd30d1e345568bb8470231d15#p525360 Remember that pathway means consisting of individual steps. For example, lets say the enthalpy of the pathway of A ->...

Chem_Mod

We think of 25 degrees Celcius and 1 atm as standard conditions. This translates into 298 K. Why do we look at this as standard conditions and see it so often? They're pretty similar to the conditions we live in. 298 K is the default temperature of delta G NAUGHT (the little 0). Delta G can change d...

Chem_Mod

Delta G (change in gibbs free energy) is a measurement at specific conditions. For example, this value might be -10 at 1 atm and 273 K. But at 5 atm and 10 K, the value for the same molecule may be different than -10. This is because this value depends on the temperature and pressure. So generally w...

Chem_Mod

Super proud of everyone who came today. Those were some tough problems, and you all bounce back from the midterms with even more expertise. next week monday is a holiday. Don't come to school. Zoom in, it's midterm week so I will still have a session: https://ucla.zoom.us/j/94689004078?pwd=YzUzc2RxT...

Chem_Mod

Chem_Mod

Here is my workshop for week 6

Chem_Mod

As always, if you have any questions please feel free to reach out!

Chem_Mod

Hi everyone! Here are the notes from last week about thermochemistry and the differentiation of the equations for different entropy equations. I have some work for some achieve questions as well. Sorry for the late post.
[attachment=0]Week 5 step up.pdf[/attachment

-Natalie

Chem_Mod

To clarify, if you would like to meet on zoom, please let me know in your email!

Chem_Mod

Hi everyone! As I mentioned in my workshop earlier today, I unfortunately have to cancel my drop in session today. Thank you so much for your flexibility and understanding! If you have a question, feel free to email me and I will respond directly, or I can set up a one-on-one zoom with you for a mor...

Chem_Mod

Correct, use the information given to determine which equation to use.

Chem_Mod

Here is my annotated constant and equation sheet and the work from the session!

Chem_Mod

Submit it asap.

Chem_Mod

Hi everyone,

As promised, here is the key for the worksheet.

Note, it is divided into two parts. Part I goes over question 1, part II goes over question 2.

Cheers,
Gabriel

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