CHEMISTRY COMMUNITY

Greetings Chem 14A students!

My name is Karen Leung, one of your UAs this quarter. For my workshops every Sunday 4-6pm from now on, I will be posting worksheets 1-2 days beforehand (I'll try to have them posted by Friday night, but Saturday by the latest). I created these worksheets as extra practice for every week's material learned. (They are also made to imitate Dr. Lavelle's question styles to the best of my ability!) If you plan on attending my workshops, please bring this worksheet (either printed or available on a computer/tablet). You do not need to complete it, we will go over the problems together during the session.

A breakdown of my workshops:
-Begin with any questions from lecture, homework, modules, etc. anything that anyone wants answered
-Review course material learned in the previous week
-Do practice problems together from my worksheets
-Answer any other lingering questions

The answers to the worksheets will be posted on this SAME post AFTER the session, but no work will be shown, so coming out to the session is necessary to understand the steps of getting to each solution. The worksheets for later weeks (Week 2,3,4..etc) will also be posted on THIS SAME post as well, so you will need to come back to this post every week for each week's worksheets.

Lastly, I have attached our first worksheet in the post below. We will be going over Fundamentals this week. Hope to see you all there! Very excited to meet everyone :))

This is perfect! I've been looking for more practice problems. Looking forward to the workshop.

Where is the workshop going to be?

Are your workshops on Sundays and Sundays only?

Would you say that these worksheet problems are somewhat similar to problems we will see on the test? Or do you think doing problems out of the textbook are more helpful in preparing for the test?

For balancing chemical equations do we need to show any work?

annabel 1 1F wrote:Where is the workshop going to be?

Covel 210. This is on the course website.

MMoreno3K wrote:Are your workshops on Sundays and Sundays only?

Yes they are on Sundays only. Other UAs also have workshops at different day/times, but not every session is identical.

Daisylookinland4B wrote:Would you say that these worksheet problems are somewhat similar to problems we will see on the test? Or do you think doing problems out of the textbook are more helpful in preparing for the test?

I write these problems from experience seeing Dr. Lavelle's exams, and some questions are adapted from his past exams ;)

Where are the posted answers for this worksheet?
Thanks

Hello, I've posted the key below for the worksheet on Fundamentals. #8 and #11 work is given since we didn't have enough time to fully go through those problems. Happy Monday!

Is this worksheet and the material included similar to what will be on this week's test?

This is very helpful! Thank you for this! I'll make sure to study it, and I look forward to seeing you on Sunday!

Thanks so much for this it was really helpful!

Thank you! This is really helpful for the first test!

Are these questions similar to those on the test this week? The worksheet obviously covers the topics on the exam but is the phrasing and level of difficulty similar?
Thank you!

This helped so much! Thank you!

I've been looking for more practice!! Thank you so much for posting this - it's very helpful!

thank you for the extra practice, it's similar to lyndon's

Do you know if other UAs will be posting their worksheets? I know that it's best to go to as many peer learning sessions as possible, but I have some class time conflicts and would like to still get a lot of practice work done.

Thank you so much Karen! I was looking for more practice problems <3

This is great! Thank you!

jordan_lo_3k wrote:Do you know if other UAs will be posting their worksheets? I know that it's best to go to as many peer learning sessions as possible, but I have some class time conflicts and would like to still get a lot of practice work done.

It's up to the discretion of the UA (ask the UA personally). I advise that if you want to attend a session but cannot make it, get a copy or notes from a friend who can.

This is going to be so helpful! The more resources the better!

Thank you! This was very helpful!

Week 2 worksheet for this week! We will go over quantum world material up to (not including) debroglie's wavelength.

Thank you so much!

Chem_Mod wrote:Week 2 worksheet for this week! We will go over quantum world material up to (not including) debroglie's wavelength.

Thank you very much, will work on these right away!

Thank you very much! This felt like great practice. Is the phrasing and level of difficult really similar to how our quizzes and tests will be?

Here is the key for this week's worksheet. Sorry for the confusion with #7 and #8 guys! See the attached document for clarification. (I've attached the steps to the solution for these 2 question; disregard the .095 on #7)

Thank you so much for these! Is the difficulty level similar to what you'd expect from the exams in this course?

Thank you! These are an immense help (especially for studying for the tests)

Thank you! This helps a ton especially since it isn't straight from the textbook.

Thanks!

Thank you very much!! These worksheets are extremely helpful

This is literally gold!

Wow Thank you

Is this going to be similar to the test next week?? Also what specific concepts do we not need to know other than Schrodinger's equation?

Adriana_4H wrote:Is this going to be similar to the test next week?? Also what specific concepts do we not need to know other than Schrodinger's equation?

As I said, I don't write the exam questions, and these are practice questions made strictly to supplement your understanding of concepts learned in class and how to apply equations. I try to write them so it's similar to exam style questions, but ultimately I don't know if it is similar, you guys will need to tell me ;)

Check Dr. Lavelle's outline of topics you need to know for each chapter on the course website: https://lavelle.chem.ucla.edu/wp-conten ... SYLL_1.pdf

Here is the worksheet for this week! We will finish reviewing the rest of the quantum world and go over the quantum numbers since it will be on Test 3.

-K

Hi!

I was wondering if we should sign up for the peer session as i wanted to attend you session tomorrow,

Thank you very much!

yast_27 wrote:Hi!

I was wondering if we should sign up for the peer session as i wanted to attend you session tomorrow,

Thank you very much!

I don’t think you need to sign up, I think you can just show up

Hi everyone! I have attached the answer key for my worksheet from yesterday. Happy studying!! :)

thank you these are so helpful!

For Quantum World Part 2 Worksheet, why is 11 D False?

Brian Cook wrote:For Quantum World Part 2 Worksheet, why is 11 D False?

I saw it as a trick question with the "always" because higher frequency doesn't matter until the threshold wavelength is reached for the photoelectric experiment. After that, it does matter, but since the wavelength doesn't always reach the minimum size for e- to be ejected, then the frequency doesn't always get to be in play.

In the first quantum world worksheet for #7, I don't understand where she got .0278 from, because wouldn't you have to add 1/16 to .03456?

These really help me out a lot! Practice makes perfect, the more to do the better. Thanks!

For question 7 on worksheet 2, why is it not possible to use the eqn in the book that says v= R(1/ni ^2 - 1/nf^2). I tried this just to see if I got the same answer and I didn't. Why doesn't this work as well, because we are using frequency to get n initial?

Can anyone explain how to do number 7 on the Quantum World Worksheet 2 the way Professor Lavelle showed us in class?
Here is the question.
An excited hydrogen atom emits light with a frequency of 1.14 x 10^14 Hz to reach the energy level for which n=4. In what principle quantum level did the electron begin?

Can someone explain what the statement in #9 of worksheet 3 means? "It is impossible to determine both the speed and position of an electron with absolute uncertainty." Why is it absolute uncertainty and not absolute certainty?

Many people have asked about #7 on Worksheet 2 and no one has responded.

Can someone please help us out and explain? The key is not clear... How did she get 1/n^2 = 0.0278 ???

ariellasarkissian_3H wrote:For question 7 on worksheet 2, why is it not possible to use the eqn in the book that says v= R(1/ni ^2 - 1/nf^2). I tried this just to see if I got the same answer and I didn't. Why doesn't this work as well, because we are using frequency to get n initial?

I think that it works as long as you add a minus sign in front of v to make it -v=R(1/ni^2 - 1/nf^2). Since the hydrogen atom is emitting light, the delta E of the electron is negative, so E=hv is negative.

annabel 1 1F wrote:Can someone explain what the statement in #9 of worksheet 3 means? "It is impossible to determine both the speed and position of an electron with absolute uncertainty." Why is it absolute uncertainty and not absolute certainty?

It should be with absolute certainty. She corrected the mistake during the session

Hi! Where do these workshops take place? I would like to attend.

Imelda Mena 1J wrote:Hi! Where do these workshops take place? I would like to attend.

Covel 210

Thank you so much Karen :)

I'm a little confused on #7 in the Quantum World Part 1 worksheet. I just can't seem to come up with (1/ni)=0.0278 and I'm not sure why. Could someone explain it to me possibly? I follow her formulas and rationale, I'm just not getting the right numbers...

AvaGordon_4F wrote:I'm a little confused on #7 in the Quantum World Part 1 worksheet. I just can't seem to come up with (1/ni)=0.0278 and I'm not sure why. Could someone explain it to me possibly? I follow her formulas and rationale, I'm just not getting the right numbers...

I only get 0.0278 if I have 7.55x10^-20 be negative like someone mentioned above, and it'll be positive because of when you divide by -hR

Hi everyone! I apologize for the lack of response, but I wasn't getting notifications for these posts for some reason - I'm so sorry! But I'm seeing really good discussion here with your classmates which is great! This is probably too late for Test 2... but to answer your questions in preparation for the midterm:

ariana_apopei4I wrote:

AvaGordon_4F wrote:I'm a little confused on #7 in the Quantum World Part 1 worksheet. I just can't seem to come up with (1/ni)=0.0278 and I'm not sure why. Could someone explain it to me possibly? I follow her formulas and rationale, I'm just not getting the right numbers...

I only get 0.0278 if I have 7.55x10^-20 be negative like someone mentioned above, and it'll be positive because of when you divide by -hR

I looked into this problem again and energy should be negative since light was emited. This should then lead you to the correct answer.

Jocelyne Milke 3G wrote:

annabel 1 1F wrote:Can someone explain what the statement in #9 of worksheet 3 means? "It is impossible to determine both the speed and position of an electron with absolute uncertainty." Why is it absolute uncertainty and not absolute certainty?

It should be with absolute certainty. She corrected the mistake during the session

Yes, this was a typo in the question #9. I mean to say with absolute certainty, not uncertainty. (Sorry - worksheets haven't been perfected yet!)

ariana_apopei4I wrote:

Brian Cook wrote:For Quantum World Part 2 Worksheet, why is 11 D False?

I saw it as a trick question with the "always" because higher frequency doesn't matter until the threshold wavelength is reached for the photoelectric experiment. After that, it does matter, but since the wavelength doesn't always reach the minimum size for e- to be ejected, then the frequency doesn't always get to be in play.

Yes. The problem never mentioned anything about the same threshold energy being compared, so higher frequency light doesn't necessarily emit electrons with higher kinetic energies. For example, if I had 2 electrons being emitted but 1 requires a higher threshold energy, it can have less kinetic energy than the other one even if a higher frequency light was used to emit it. Think about the photoelectric effect equation.

Here is this week's worksheet, we are finishing chapter 2, going over electron configurations and trends in the periodic table.

Hi everyone,

I have attached my notes on periodic table trends since I had to rush through this portion and go over time today. For those of you who needed to leave, I hope the notes will be able to fill you in! Discuss with your classmates (especially those who stayed until the end of the session) if there is anything unclear in them.

I have also attached my version of the worksheet answers due to needing to go over time for the session, but there's not too much work shown since these topics are pretty conceptual. If there is any confusion, bring them to drop in/office hours!

Thank you for this. I really need the extra practice.

Hi! Can you post the 4th worksheet key? And also do you have a worksheet with more Lewis Structures practice?

Sophia Fox 4B wrote:Hi! Can you post the 4th worksheet key? And also do you have a worksheet with more Lewis Structures practice?

Key has been posted above ^ (answers are handwritten)

Happy (approaching) week 6! :D

As preparation for your midterm, I have made a comprehensive worksheet of different material that may show up on the midterm this week. However, we will go over new material that I haven't reviewed in previous weeks first, and if time permits, we will go over the review problems on cumulative material afterwards.

Just like my co-UAs', the questions are modeled after previous test and exam questions, but it may not have everything you need to know. This worksheet is not indicative of the structure, length, or format of the actual midterm :)

I hope to see you all there, come early so you can grab a good seat!

*** EDIT: #11 is NH4+ and NO3-

Heyy I was wondering where I can find the answers for worksheet 5 (newest one)? Also for question 9 aren't there more than 2 ions that aren't isoelectronic with F-. I got 4 ions (Li+, Be2+,O-, N2-) that aren't isoelectronic.

Thanks!

Has the key been posted for midterm review worksheet #5?

Kenan Kherallah 1A wrote:Heyy I was wondering where I can find the answers for worksheet 5 (newest one)? Also for question 9 aren't there more than 2 ions that aren't isoelectronic with F-. I got 4 ions (Li+, Be2+,O-, N2-) that aren't isoelectronic.

Thanks!

I also got this as my answer! I think the answer sheet will be posted tonight after the session is held.

Joussie Camacho 4I wrote:Has the key been posted for midterm review worksheet #5?

I think it will be posted after the session ends. (It ends at 6)

Here is the key for the midterm review worksheet! Good luck tomorrow! :)

Thank you!

For 6.b. isn't it asking for the work energy/ the threshold energy? In the solution, E=hv is used to find energy, but I thought that was energy of the incoming photon and it's asking how much energy is required to remove the electron. So wouldn't you find the kinetic energy of the photon using the given velocity and the mass of an electron and then use the formula (E=hv) - work energy = Ek?

So wouldn't you subtract that 1.66x10^-17 J from the kinetic energy to find the work energy?

For #8, which asks for the full electron configuration of Nitrogen, would 1s^22s^22p^3 be wrong? Do we have to write out 2px^1 2py^1 2pz^1?

Joussie Camacho 4I wrote:For #8, which asks for the full electron configuration of Nitrogen, would 1s^22s^22p^3 be wrong? Do we have to write out 2px^1 2py^1 2pz^1?

I don't think so, I believe thats just an easier way to write it to visualize unpaired electrons

Thank you for your help!

Joussie Camacho 4I wrote:Thank you!

For 6.b. isn't it asking for the work energy/ the threshold energy? In the solution, E=hv is used to find energy, but I thought that was energy of the incoming photon and it's asking how much energy is required to remove the electron. So wouldn't you find the kinetic energy of the photon using the given velocity and the mass of an electron and then use the formula (E=hv) - work energy = Ek?

So wouldn't you subtract that 1.66x10^-17 J from the kinetic energy to find the work energy?

I think since it tells you the freq (2.50x10^16 Hz) youre looking for the energy of the photon that will reach that threshold. I also thought I had to do the work energy but the energy of the photon must at least equal the work function for the e- to be ejected, so you'd just find the E of the photon.

Thank you Karen! This is super helpful for preparing for the midterm today!

On the midterm review worksheet, could someone explain how to draw the lewis structure for XeO2F2?

Daisylookinland4B wrote:On the midterm review worksheet, could someone explain how to draw the lewis structure for XeO2F2?

Xe should be the center atom, with 2 F's and 2 O's attached to it. The total number of electrons should be 34e-, so there should be one bond between Xe and the F's, and each F should have 3 lone pairs, since F is unlikely to form a double bond. Each O should have 2 lone pairs and two double bonds to Xe to minimize formal charge. Since there's still 2 electrons left, you can place them as a lone pair on Xe, since Xe has an expanded octet and can hold more than 8 electrons.

Hi Karen! Will you still be holding a workshop this Sunday (over Veteran's Day weekend)?

Josephine Lu 1L wrote:Hi Karen! Will you still be holding a workshop this Sunday (over Veteran's Day weekend)?

Yes, all sessions in Covel 210 will be running as normal. Worksheet will be posted in a bit. Sorry for the delay!

Hello everyone, here is the worksheet for my workshop later today. Today will be a brief session finishing up properties of chemical bonds and going over VSEPR structures. (should be a quick and simple session!) I will be saving hybridization topics to go over next week, since I am expecting people to be off campus this weekend.

Hope everyone is having a great long weekend!

Best,
Karen

Thank you Karen! this was very helpful for the midterm.

Thank you again! These are always so helpful. When will you be posting the answer key to worksheet 6?

Here's the key for Sunday's worksheet.

There were a lot of questions on polarizability, and I found this link to be a decent resource:
http://wwwchem.uwimona.edu.jm/courses/C ... ajans.html

Last week we left off on hybridization, which we will go over this week and will be on Test 3. I will NOT be holding workshops over Thanksgiving break, which means that I will not see you all until after Test 3. However, I should have covered everything that will be on Test 3 by tomorrow.

Almost there!

-K

Thank you so much! When will you be posting the key for this worksheet?

Chem_Mod wrote:Last week we left off on hybridization, which we will go over this week and will be on Test 3. I will NOT be holding workshops over Thanksgiving break, which means that I will not see you all until after Test 3. However, I should have covered everything that will be on Test 3 by tomorrow.

Almost there!

-K

Thank you for posting this week's worksheet, is there any way you can post the solutions by Monday. Also, can you create/post a list of important topics to study for Test 3? Thank you once again!

Key for Week 7's worksheet. Have a great Thanksgiving break everyone!

Thank you again for posting these worksheets!

Hello Karen! If you went over any notes (wrote stuff on the board) on Sunday, could you please send those notes? Thank you so much!

Josephine Lu 1L wrote:Hello Karen! If you went over any notes (wrote stuff on the board) on Sunday, could you please send those notes? Thank you so much!

My notes are supplementary to my workshops and require attendance to fully understand since I do verbally explain more than I write down in my notes. Thus to avoid confusion with students who did not attend, I do not post my notes unless there were special circumstances (went over time during session, held during holiday weekend, etc.), and even then, I rewrite them more detailedly and comprehensively when I do post them. Your best shot is probably to ask a classmate who did attend and took notes if you do find notes from my session helpful!

Thank you very much for these worksheets!!

thanks!

Thanks!

thanks!

Thank you so much--this is so helpful!

thank you!!

These are so helpful, thank you!

Is there any worksheet for test 3?

These worksheets have helped me so much on the tests, will there be any covering the topics for Test 3?

Riya Shah 4A wrote:Is there any worksheet for test 3?

I believe worksheet 6 and 7 help with test 3 since it has the material that the test is going to cover but she said she won't be giving a specific worksheet for test 3 since the past 2 are enough. These worksheets are really helpful and if you scroll up, they're easy to find.