CHEMISTRY COMMUNITY

Angel More

I'd recommend getting the Coursicle app and tracking when people drop the class so you can enroll in it. I haven't used it but I have heard that people who have used it have been able to snag the class they wanted.

Angel More

I am taking Chem 14BL, LS30B, and 2 GEs!

Angel More

I love going swimming, really clears the mind and it's nice to go outside

Angel More

I love trader joes and all of their snacks. Personally I am craving the trader joes cassava chips with the trader joes romesco sauce.

Angel More

Doing all the textbook problems and understanding them. Also for 14A the TAs had review sessions, I would assume they are doing review session this quarter too and I would recommend going to them.

Angel More

SophiaNguyen_2L wrote:Hi! All these answers are super helpful, so thank you all. When calculating the mols of gas in the PV=nRT equation, which temperature would you use when they give you and initial and final temperature? Thank you!

You want to use the initial temperature when calculating the mols of gas

Angel More

For 3NO2(g)+H2O(l)↽−−⇀2HNO3(aq)+NO(g) I got K=1.7×10^9 1) First we want to find the standard Gibbs free energy ΔGr =[2ΔGf(HNO3) + ΔGf(NO)] − [3ΔGf(N2) + ΔGf(H2O)] - then plug in the given values ΔGr = −52.75kJ/mol -then convert to J ΔGr = −5.275×10^4J/mol 2) Next we want to find the equilibrium cons...

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ΔS > 0 -- Solid to liquid, liquid to gas, and solid to gas have positive changes in entropy ΔS < 0 -- Liquid to solid, gas to liquid, and gas to solid all have negative changes in entropy ΔH > 0 -- Solid to liquid, liquid to gas, and solid to gas all have positive changes in enthalpy ΔH < 0 -- Liqu...

Angel More

You would use this equation:

ΔS = qrev/T

Then just plug in the values you were given (remember to convert seconds to hours and Celsius to Kelvin):

ΔS = (81.0 J/sec * 60 sec/min * 60 min/hr) / (25.3+273.15)K = 977

Angel More

I'm taking Chem 14BL, LS30B, a Writing 3 class, and maybe a fiat lux!

Angel More

Hi, on the constants and formulas sheet (https://lavelle.chem.ucla.edu/wp-conten ... ations.pdf) we are given Ideal gas Cp, Ideal gas Cv, Cp of water, and Cp of ice.

Angel More

You would use this equation: E = q +w, and rearrange to solve for q: q = E - w. Then plug in your values. w=-346 J because work is done by the system, and E = + 7545 J since there was an increase in internal energy. q = 7545 J - (-346J) q = 7891 After finding q you would use it to find specific heat...

Angel More

So we can set the heat gained by the cold water to the heat lost by the hot water m(cold water) * c * ΔT(cold water)= -m(hot water) * c * ΔT(hot water) and from here we can just plug in the values. *remember that c = 4.184J/gC & ΔT= Tfinal - Tinital (270.0g) * (4.184J/gC ) * (Tfinal - 25.00C) = ...

Angel More

You would use this equation: E = q +w, and rearrange to solve for q: q = E - w. Then plug in your values. w=-346 J because work is done by the system, and E = +6055J since there was an increase in internal energy. q = 6055J - (-346J) q = 6401 After finding q you would use it to find specific heat us...

Angel More

So we can set the heat gained by the cold water to the heat lost by the hot water m(cold water) * c * ΔT(cold water)= -m(hot water) * c * ΔT(hot water) and from here we can just plug in the values. *remember that c = 4.184J/gC & ΔT= Tfinal - Tinital (230.0g) * (4.184J/gC ) * (Tfinal - 25.00C) =...

Angel More

So we can set the heat gained by the cold water to the heat lost by the hot water m(cold water) * c * ΔT(cold water)= -m(hot water) * c * ΔT(hot water) and from here we can just plug in the values. *remember that c = 4.184J/gC & ΔT= Tfinal - Tinital (230.0g) * (4.184J/gC ) * (Tfinal - 25.00C) = ...

Angel More

And then when it comes to reactions you can look at the bond strengths to figure out if the reaction is endothermic or exothermic. (This is asked in Sapling Week 3/4, questions 4.) We know that an endothermic reaction has a large energy requirement, with a small energy release. So for an endothermic...

Angel More

An endothermic reaction has a large energy requirement, with a small energy release. So for an endothermic reaction it would have stronger reactant bonds and weaker product bonds. For example, for a reaction: B2+C2⟶2BC, B–B and C–C bonds are stronger than B–C bonds so it would be endothermic. An exo...

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Endothermic: large energy requirement, with a small energy release. So for an endothermic reaction it would have stronger reactant bonds and weaker product bonds. For example, for a reaction: B2+C2⟶2BC, B–B and C–C bonds are stronger than B–C bonds so it would be endothermic. Exothermic: small energ...

Angel More

Yes so to do this problem you would use the equation that gives the heat lost or absorbed q=c*m*ΔT and we can state that qwater=−qmetal, so you can set up the equation as m(water) * c(water) * ΔT(water)= −m(metal) * c(metal) * ΔT(metal) **also remember that ΔT = (Tfinal - Tinitial) using what you we...

Angel More

My current favorite song is Everyday by ASAP Rocky & Rob Stewart. I would say my current go to artists are Mac Miller, Peach Pit, Roy Blair, & Steve Lacy. For me the best way to discover new music is my Spotify discover weekly playlist and also Tiktok!

Angel More

Does anyone have a good/ established structure they would want to share when they would study for Chem 14B? I just want to make sure I'm knocking everything to prepare me well for the exams. I really recommend the textbook and sapling problems. Based on Chem14A it seems like Lavelle tends to pull q...

Angel More

I would just focus on the questions assigned. Lavelle tends to pull from the assigned textbook problems when making his exams!

Angel More

I'm not sure if that equation is correct, but the way I did it was I got the equation (0.154-x)/x^2 = 0.0032. Then, I rearranged the equation so that it becomes a quadratic. It should look like this: 0.032x^2+x-0.154. Then, you just use the quadratic to get the x value. And you must use the most re...

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Going off of what Hana said the zoom is on an external device. Most people used their phones to show their workspace and took the exam on their laptops.

Angel More

Last time we were sent links prior to our exams. I think that is how it is going to be this time as well!

Angel More

You set up the equation like ka = [H+][A−]/[HA] ka = x^2/(initial moles) - x then your equation will be x^2 + 0.00459x - (0.00459*.14) x^2+0.00459x-6.426E-4 Your roots will be x = 0.02315823, −0.02774823 The equation for percent ionization is ([H+]equilibrium/[HA]initial) * 100. You will want to use...

Angel More

Yep, calculators are allowed for all exams!

Angel More

Does anyone have a good/ established structure they would want to share when they would study for Chem 14B? I just want to make sure I'm knocking everything to prepare me well for the exams. I really recommend the textbook and sapling problems. Based on Chem14A it seems like Lavelle tends to pull q...

Angel More

No class that day due to midterm. :-) Hello :) Are there any accommodations in place for international students for the midterm like there is for the final? Thanks in advance! Oh! It seems like Lavelle will make an announcement about this soon https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=160...

Angel More

You can check the box under options "Notify me when a reply is posted" if you want to get replies. This box is right under the submit button.

Angel More

No class that day due to midterm. :-) Hello :) Are there any accommodations in place for international students for the midterm like there is for the final? Thanks in advance! It seems like there is an alternative time for the final exam but not for the midterms (Sunday March 14, 8am-9:30am). Thoug...

Angel More

Agree with what everyone said above. I would recommend to wait a couple of days for the CCLE grades section to update since the TAs have to enter the grades and it sometimes takes a couple of days before everything is added in.

Angel More

You can also access the worksheets from this link if you want more practice and can't make it to the workshops. https://drive.google.com/drive/folders/ ... ODsKNCF5fe

Angel More

There is also a link with all worksheets if you missed the session but still want the practice. https://drive.google.com/drive/folders/1-iUlSUXyOWLHC5chqYRLC2ODsKNCF5fe are these from each step session or is it just one ? these are from a few different step up sessions (it might be all). they have ...

Angel More

When using ICE tables make sure your values are concentrations, your units should be moles/liters.

c= n/V

Angel More

Sorry if this has already been addressed somewhere, but are the midterms/finals only during lecture times, or can they be taken at alternate times if you are in a different timezone? I took 14A over summer so I'm not sure how it works. Thank you! Our exams are during the Friday lecture timeslot, bu...

Angel More

There is also a link with all worksheets if you missed the session but still want the practice.
https://drive.google.com/drive/folders/1-iUlSUXyOWLHC5chqYRLC2ODsKNCF5fe

Angel More

In general, don't include anything that is a solid or liquid or solvent in your calculations.

Angel More

Hi, what does it mean when the equilibrium is shifted to the right/left? How would that reflect in K?

This is question 31 & 32 on the 1A module.

Angel More

I am also starting to worry about my grade. I also don't like how there isn't anywhere we can check what grade we have in the class currently. I am not used to that. There is a way to check your grade! Go to the grades section of the CCLE site. There you will see all the points you got. Add up all ...

Angel More

THANK YOU DR. LAVELLE!!! I am looking forward to next quarter: Chem14B. :D

Angel More

What are you guys doing over winter break? Also do you have any good book or movie recommendations?

I am going to be road tripping down the Pacfic Coastal Highway with my family in an RV (social distancing at its finest). I am super excited to visit a bunch of beaches and escape my house. :)

Angel More

This was my first UCLA quarter and it was crazy to me how fast the quarter went and how much work there was. Honestly, I know that I could have done better and I want to set up a plan for next quarter (and the quarters to come) so I will stay on track. I think the main thing with motivation is knowi...

Angel More

Like you I plan on doing the textbook problems earlier and going to UA sessions etc. I will also utilize chemistry community more and use the worksheets that UA's and TA's post on here. Also we get points for the posts we make in the next two days because chemistry community was down for the past t...

Angel More

Yes you are correct, it would be neutral!

Angel More

I asked my brother he had some sodium hypobromite, but he said NaBrO.

Angel More

Good luck on finals and hope everyone has a great and restful winter break !

Angel More

I was def rushed so I am glad that we were able to get 10 points back.

Angel More

I am reflecting on this quarter and my study habits to see what went well and how I could do better. For Chem 14B I plan to focus a lot more energy on the textbook problems and gaining a solid understanding of each problem. I also hope to attend more office hours and UA sessions. What are some thing...

Angel More

I am so relieved that we got through this chem quarter! I am also really happy that we are getting 10 points extra on the final. Just a few more finals to go for me and then winter break!

Angel More

I also got the same thing! I was looking for the answers too :)

Angel More

As everyone said above you can go to your TA's office hours or make an appointment with them and they will walk you through what you got wrong (but they do not show you the exam/share their screen they just talk it out). I highly recommend this as it was helpful for me to know what I should review -...

Angel More

The Friday review session will be during "class" so that means it will be posted where all our other lectures are on Friday.

Angel More

When asked for the expected bond angle do we say less than [angle] and when asked for the predicted bond angle do we just say [angle]? For example when asked for the predicted bond angle for a linear shape the answer would be 180 and then when asked for the expect bond angle for a linear shape the a...

Angel More

I think it is helpful to know that en/ethylenediamine has no charge, it is neutral.

Angel More

Breakdown of the grade: Sapling - 50 pts Chemistry Community - 50 pts Midterm 1 - 110 pts Midterm 2 - 110 pts Final - 180 pts Total 500 pts You can calculate your grade (assume what you will get from sapling & chem community) and estimate you final grade. You can also use this to figure out your...

Angel More

To get full credit you have to have at least 5 points each week. You cannot skip weeks and just get more points the next week, the grading scale is based on each week.

Angel More

Excerpt from this doc (https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/Final_Review_Sessions_14A.pdf): Final is same format as midterms. All tests are proctored and closed book. CCLE link will be under folder called FINAL. Final is 90 minutes with 30 questions each 6 points (180 po...

Angel More

As everyone said above you can go to your TA's office hours and they will walk you through what you got wrong (but they do not show you the exam/share their screen they just talk it out). I highly recommend this as it was helpful for me to know what I should review -- I thought I understood certain ...

Angel More

I think we are supposed to memorize them. Here is a list of them all with the charges https://sites.google.com/site/chempendix/ligands

Angel More

As for the format of the class it is still up in the air according to these posts by Lavelle:

1) viewtopic.php?t=67049
2) viewtopic.php?t=67067

Angel More

This might be a dumb question but how do you know the charges of the atom on the outside of the brackets? For example:

Na[Ag(CN)2], here Na has a +1 charge. How do we know that and how can we figure out other atom charges?

Angel More

I struggle with this too! Sophia gave a lot of great tips. I think it's a lot of playing around with moving things and seeing what could work: changing double bonds to single bonds with electron pairs. Unfortunately there is no set steps on how to find resonance, but practice will help you get faster.

Angel More

Since there is so much more time, do you guys think he will make the test harder but keep the same amount of questions or make the test the same but add a lot more questions? I think the test will have more questions. Since he gives up ~5 minutes per question and the final is 90 minutes then maybe ...

Angel More

Based on the website the test will be on December 13th from 11:30 to 1pm - that is a Sunday. I am guessing that it will be a similar setting like our midterms.

Angel More

I am going to start studying for the final this coming week -- week 9. I am just going to start by re doing the textbook problems and making a cheatsheet/guide on how to do all types of problems so it will be easy to remember how to tackle problems. I also am going to be attending UA sessions throug...

Angel More

I feel like overall it has been going well. I like with this class there are a lot of ways to practice what we are learning -- UA sessions, textbook problems, chem community, and sapling. I started a little shaky on the first exam but I improved on this recent exam as I understand how to study bette...

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I am going to redo the textbook problems since he pulls his questions from there. I am also going to read through the sapling questions and answers. I also have heard that the UAs give out practice exams and they might be giving out practice final exams.

Angel More

Check these posts by Lavelle out for all your questions about 14B:

- viewtopic.php?t=67049
- viewtopic.php?t=67067
- https://lavelle.chem.ucla.edu/wp-conten ... stions.pdf

Angel More

AsF3 would have a higher boiling point than AsF5 because it is a polar molecule that has Dipole-Dipole and LDF. AsF5 only experiences LDF because all of the Fluorines are pulling it equally. Could you please walk me through how you realized that AsF5 is a polar molecule? Hey! Sorry AsF3 is the pola...

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Organic compounds always contain carbon while inorganic compounds contain metal and other elements.

I'm working through the textbook problems now and will reply if I find any about this topic.

Angel More

Selena Quispe 2G wrote:AsF3 would have a higher boiling point than AsF5 because it is a polar molecule that has Dipole-Dipole and LDF. AsF5 only experiences LDF because all of the Fluorines are pulling it equally.

Could you please walk me through how you realized that AsF5 is a polar molecule?

Angel More

I know we are all worried, but we got this!! Just a few more weeks.

Angel More

Thanks for clearing that up guys!

Angel More

Oh ahhhh that makes more sense, thank you guys!

Angel More

To add on in terms of periodic trends Polarizability decreases as it goes across a period and increases as it goes down a group. This is because the greater the number of electrons, the less control the nuclear charge has on charge distribution, and thus the increased polarizability of the atom. As ...

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For textbook problem 2A.5 it asks to give the ground-state electron configuration expected for Cu+ I thought the answer would be [Ar]3d^8 4s^2 since 4s has a lower energy than 3d and would fill up first. However the answer is [Ar]3d^10. Why doesn't the 4s fill up first? What is the order of the elec...

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How do you know if the quantum number ms (spin) is +½ or -½? Is the purpose of knowing that ms can be +½ or -½ only used for know that the arrows in the electron configuration have opposite spins?

Angel More

Lavelle is accepting everyone off of the waitlist. Lavelle is not sure if the class will have asynchronous lectures next quarter. Check these posts by Lavelle out: - https://lavelle.chem.ucla.edu/forum/viewtopic.php?t=67049 - https://lavelle.chem.ucla.edu/forum/viewtopic.php?t=67067 - https://lavell...

Angel More

What are the different type of bonds do we need to know for the MT2 and how do they differ?

Angel More

I enjoy swimming in the ocean, going on hikes, and not going to lie TikTok dances are a workout!

Angel More

I think you are asking the difference between bond dipole/dipole moments formula and dipole-dipole forces. Dipole-Dipole Forces are intermolecular attractions between two molecules. They are the weakest bonds and all polar covalent compounds have them The dipole moments formula measure the polarity ...

Angel More

To add on even more, polarizability tends to decrease from left to right since the atomic radius and the number of electrons decreases.

Angel More

The only equation that I think we will need to know is Formal Charge: Formal Charge of Atom = V - L - B/2 - V - Valence Electrons of Atom - found using the periodic table of elements - L # of Lone Electrons on Atom - these are the lone individual electrons - B/2 # bonded electrons with Atom/2 - each...

Angel More

Deep breathes throughout the whole test. Also remember that you have prepared, you just have to show your learning here. Take it slow and read the questions veryyy carefully.

Angel More

In Lavelle's 17th lecture he said you will not need to calculate dipole moments. Just know that increase in bond length increases the dipole moments.

Angel More

The polarizing power increases from left to right across a period and decreases down columns of the periodic table.

Polarizability decreases from left to right and increases down columns of the periodic table.

Angel More

We know that a hydrogen bond forms when there is a hydrogen bonded to two very electronegative molecules. Both a nitrogen atom and oxygen atom, with an unshared pair of electrons, can form a hydrogen bond by bonding to a hydrogen (of a water molecule). Also, if a Hydrogen is already bonded to nitrog...

Angel More

You find formal charge using this formula: Formal Charge of Atom = Valence Electrons of Atom - # of Lone Electrons on Atom - # bonded electrons with Atom/2. - Valence Electrons of Atom - found using the periodic table of elements - # of Lone Electrons on Atom - these are the lone individual electron...

Angel More

Yep have to memorize but here is how I remember it:

Freddy Can't Vacant Nashville Before 2

FC = V - N - B/2

Not sure how helpful that is for you, but it sticks in my head.

Angel More

I recently binged Grand Army and The Queen's Gambit on Netflix. would recommend both!

Angel More

Can you explain the difference between h (6.62607015×10−34) and ħ (h-bar) (1.054571817×10−34) to me please?

And when do we use the 1) formula and the 2) formula?

1) ∆p ∆x ≥ h/4π
2) ∆p ∆x = (1/2) ħ

Thank youuuuu

Angel More

These 2 make me kinda sad :( But the drawings are cute.

Angel More

You should use the ones he emailed us.

Here are the links to them

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

Periodic Table: https://lavelle.chem.ucla.edu/wp-conten ... _IUPAC.pdf

Angel More

Hey Guys I thought I would share this tip. I recommend storing constants in your calculator so you don't have to type them out all the time. This helps me be faster and not make silly mistakes (like incorrectly copying the constant value). How to do this is: 1) Enter the number in your calculator 2)...

Angel More

I think it is best to worry about that if it continues to happen after the due date since it will probably update everything once it is all due.

Angel More

My guess is that you would be fine with just reading the textbook. From my understanding the textbook problems are the ones the exam is based on so making sure you understand that would be best. Also doing the audio visual practice problems.

Angel More

The atomic radius of atoms generally decreases from left to right across a period.And increase from top to bottom. Check out the image I attached. Also the gain of an electron adds more electrons to the outermost shell and the pull towards the nucleus so the pull becomes slightly weaker so it causes...

Angel More

I love the music! It is so fun.

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