CHEMISTRY COMMUNITY

Kaiya_PT_1H

This question asks whether Eº or E is temperature dependent, and the solution manual says both are temperature dependent. how can Eº be temperature dependent if by definition it is at 298K?

Kaiya_PT_1H

how is O3-->O2 the reduction reaction if both sides have the same oxidation number of 0?

Kaiya_PT_1H

Like a lot of other people, I couldn't get into 14C :/ but hopefully next quarter or I might take it in the summer!

Kaiya_PT_1H

I definitely miss seeing people in person and walking around campus, and of course the food like everyone has been saying :) For those around Westwood (or planning to visit), I just figured out that you can still buy stuff from Bcaf with a credit card, so I'm planning to get a lot of smoothies next ...

Kaiya_PT_1H

You automatically get enrolled if people drop the section you're on the waitlist for, so it just depends on your position on the waitlist. Like other people said, more people tend to drop at the beginning of the quarter so I wouldn't worry too much about it right now!

Kaiya_PT_1H

abby hyman wrote:I think it will be based on the amount of time we covered each topic but I also think that there will be a significant amount of questions from after midterm 2 specifically

Yeah my TA said in office hours that it would be more heavily focused on material from after midterm 2!

Kaiya_PT_1H

We can use the equation k = Ae^(-Ea/RT) to solve for this problem. Temperature values in Kelvin are given, so is activation energy E for the forward and reverse reactions. R is a constant 8.3145. (k catalized reaction)/(k uncatalized reaction) = (A*e^(-Ea1/RT))/(A*e^(-Ea2/RT)) goes to (e^(-Ea1/RT))...

Kaiya_PT_1H

I think it's by the end of the quarter, so you should be fine! clearly several of us are using the same strategy haha

Kaiya_PT_1H

I am definitely planning on dorming during the fall, but I really hope they don't plan on doing triples because I remember that I was forced to take a triple before COVID happened. They said a while ago that they weren't going to have triples, I think. https://dailybruin.com/2021/01/20/ucla-plans-f...

Kaiya_PT_1H

Like other people said you could go to any TA, but it would be good to let them know via email in advance!

Kaiya_PT_1H

I wouldn't worry about it too much if I were you! It's a lower-division class in your first year during a pandemic, so I think they'll understand the circumstances and everything. Like other people said, there are other important things that will make you a well-rounded applicant, so this one quarte...

Kaiya_PT_1H

I'd been feeling pessimistic about school recently, but I recently decided that I want to double major so I'm excited to start learning something new :) I usually walk to campus when I'm feeling down or just watch some TV to relax.

Kaiya_PT_1H

Sharetea is always good for boba! Fat Sal's is definitely a UCLA classic, and Nick the Greek opened a few months ago and is also really good :)

Kaiya_PT_1H

I've been listening to a lot of NIKI recently, especially Plot Twist and lowkey :)

Kaiya_PT_1H

I do copy editing for Daily Bruin and I'm also in the Undergraduate Science Journal!

Kaiya_PT_1H

Thanks for asking this question! I was also confused about how to approach this problem since I felt like it should be more complicated than this, but I think I might just be overthinking problems at this point.

Kaiya_PT_1H

Yes, you would use the Nernst equation but you would use a combination of concentration values and partial pressures when solving for Q so it's a little different than what we're used to! Q = PH2/[H+]^2 Hope that helps! Why are we allowed to do pressure/concentration if the units don't match up? Is...

Kaiya_PT_1H

The max is 50, otherwise I think people would be posting a lot more for extra credit :)

Kaiya_PT_1H

Has he said anything about the number of points needed for a B? I didn't see anything about it in the syllabus.

Kaiya_PT_1H

My TA also said to focus more on the stuff we're learning in weeks 7-10 since we've already been tested on material from weeks 1-6, but I do think it would be a good idea to go over the syllabus problems again as review!

Kaiya_PT_1H

I'm just planning to do chem 14C, chem 14BL and physics 5C. it's only 12 units but it seems like a lot of work with 2 labs and everything...

Kaiya_PT_1H

I went through all these steps, but my answer is still 1.508 kJ/mol which doesn't match the textbook. the heat attributed to the temperature change is just the q of the water increasing in temperature, right?

Kaiya_PT_1H

Thanks Sophia, this was super helpful!

Kaiya_PT_1H

Use the first law of thermodynamics: delta U=q+w. Use the ideal gas law pv=nrt to find-p*deltav (note that temperature is 298k and you would manipulate it so that -p*delta v=-delta n*r*t). Work is equal to -p*delta v and q is equal delta h at constant pressure. what would you do here for the change...

Kaiya_PT_1H

Ria Nawathe 1C wrote:Yes, that's the equation you use! Delta U = 982 J = 492 J + w, so w = 982 J - 492 J = 490 J. Hope this helps!

okay thank you! I was just confused because in the textbook it said the answer was 90 x 10^2 J. maybe a typo?

Kaiya_PT_1H

The internal energy of a system increased by 982 J when it was supplied with 492 J of energy as heat. (a) Was work done by or on the system? (b) How much work was done? My answer for part b of this question doesn't match the textbook and I'm confused. To find how much work was done, don't you just u...

Kaiya_PT_1H

Question 4A.1 has 6 examples of open/closed/isolated systems, and it's good practice to identify them. An open system allows matter and energy to be exchanged, a closed system only allows energy to be exchanged, and an isolated system is entirely self-contained. So any question that involves removin...

Kaiya_PT_1H

I think that it is up to your TA to check and account for how many posts you have made in the past week so it might be best to talk to your TA. I don't think its like the sapling homework where it automatically logs it into the grade book. Yeah I think Lavelle said in his email they're updated manu...

Kaiya_PT_1H

Hello! Something I find really helpful is really just going through the textbook and assigned readings. The textbook really breaks down the different equations, which is something I struggle with. Going through the example boxes and making sure you understand everything that is being done is super ...

Kaiya_PT_1H

Thanks for this! I felt the same way and this was really helpful.

Kaiya_PT_1H

As other people have said, I think the best way to go is to do all the homework problems in the outlines and make sure you understand how to do them. I also find it helpful to explain concepts out loud to people or write them out.

Kaiya_PT_1H

I have no idea, but a lot of the chemistry community questions are just questions from the textbook or TA/LA sessions so I think it just goes back to studying those to prepare for the tests.

Kaiya_PT_1H

Thanks guys!

Kaiya_PT_1H

This can also be extended to baking!! I like to experiment with cookies, because every single ingredient can completely alter your cookie! Since baking soda is a base (sodium bicarbonate as we know), it is often used in recipes that use some kind of acid like lemon juice in order for your product t...

Kaiya_PT_1H

It's a bit late to ask this obviously, but we just get points for a total of 50 posts in chemistry community, right? As opposed to actually posting 5 times per week?

Kaiya_PT_1H

Does anyone have a good mnemonic/hack for remembering the formulas of the strong acids and bases?

Kaiya_PT_1H

Hey Lillian, I get it! I've been having the same problem where I just feel physically incapable of doing work sometimes, which is... not great. I like to make lists of what I have to do and when the things need to be done by, and I find it helpful to break up large tasks ("study for midterm&quo...

Kaiya_PT_1H

Jaclyn Dang 3B wrote:I heard that it was really manageable since being online. I am not sure however if there are synchronous meetings.

I was wondering about this too, can anyone explain how 14BL online works?

Kaiya_PT_1H

Yeah I think this is true for monoprotic acids, which is mostly what we work with in class!

Kaiya_PT_1H

Looks like there's one pretty old one from Lavelle on here, but nothing super recent https://www.bruintestbank.com/chemistry/

Kaiya_PT_1H

Last time we were sent links prior to our exams. I think that is how it is going to be this time as well! Do you remember where this was posted on CCLE? Or was it his website? Or possibly by email? Haha I have never taken a midterm with Professor Lavelle before and I'm a bit nervous... They were on...

Kaiya_PT_1H

Naomi Hernandez-Ramirez 1J wrote:Hi guys, so what im taking from this is basically ti study/ understand how to do textbook problems because they are similar to what the midterms will be like?

Yes! as other people said, sometimes questions are even taken directly from the textbook for the midterm.

Kaiya_PT_1H

Last quarter he also made a separate CCLE tab just for midterm/final content, so he might do that for the links!

Kaiya_PT_1H

There's also a WEPA printer (like on the hill) at Weyburn Commons! You can pay with your Bruincard and select files from Google Drive and all of that.

Kaiya_PT_1H

He also has discussions on Tuesday at 4 pm and Wednesday at 5 pm!

Kaiya_PT_1H

I don't think the Ka/Kb values would need to be memorized, but memorizing the strong acids/bases would probably be helpful. you can always check the constants and equations sheet on the website if you want to see what information you'll be provided with on the test! but I think Ka/Kb values would be...

Kaiya_PT_1H

Definitely do the problems in the outline, some of them are exactly the same as questions on the test and lots of people post in chemistry community about them so it's likely that someone will be able to help you out if you have a question! Also make sure to review any special cases/exceptions to ru...

Kaiya_PT_1H

Hey! I actually had a similar question to you, for me my x values were 0.235 and 5.78, I subbed in x=0.235 and got the right answer but I'm not sure how to know which value to eliminate. I guessed x=0.235 because it's a smaller value, but if anyone knows how in general to determine the right value ...

Kaiya_PT_1H

Is it realistic to have a very large K value for this question? also, is there only one combination of equations that would work or are there multiple?

Kaiya_PT_1H

Not sure if this helps, but I spent a long time on this trying to do the quadratic formula when you can just square root the Kc formula and the value for Kc to solve for x.

Kaiya_PT_1H

Thanks Kaylee and Sydney, I was confused on this problem as well and your instructions were helpful!

Kaiya_PT_1H

Will he still be posting lecture videos on the days of the midterms?

Kaiya_PT_1H

Thanks everyone!

Kaiya_PT_1H

There's an app called Forest I use to help me get off my phone, and it also has good ambient sounds for studying!

Kaiya_PT_1H

I believe grades have to be in by the week after finals week, but I don't think it will take that long considering that this test is multiple choice.

Kaiya_PT_1H

Good luck everyone! Only a few days left before we can all enjoy our winter break :)

Kaiya_PT_1H

Can someone explain to me how oxalate could be bidentate? I think I might be drawing the lewis structure wrong or something. it's section 9C, question 5, part D.

Kaiya_PT_1H

Claire_Kim_2F wrote:I noticed that oh2 is also considered aqua if it is in the coordination compound is that true?

yeah I think that's what other people above were referring to

Kaiya_PT_1H

I'm worried because I feel like my study habits are getting worse in this class, and that's only going to continue with 14B. I'm hoping next quarter with some schedule changes it'll be more manageable.

Kaiya_PT_1H

He emails us when he updates the point totals and lets us know what amount is sufficient!

Kaiya_PT_1H

I think there are past midterms and finals for 14A online, but not for Lavelle specifically. Could be worth looking into for extra practice though!

Kaiya_PT_1H

I've definitely focused more on the textbook problems than lecture notes or anything else, and it's worked for me so far. However, I've noticed that sometimes he puts specific things from the lecture in the midterms so that's something to look out for.

Kaiya_PT_1H

Sheryl Ocampo 1D wrote:I thought I was the only one thinking about this

same!

Kaiya_PT_1H

Ariana Flores 3F wrote:I am currently waitlisted as well, does anyone know if this means we don't need a PTE number or we are automatically sent one?

I don't think you need a PTE number, they'll just change your status in the class to enrolled! I could be wrong though so just check in as it gets closer to winter quarter.

Kaiya_PT_1H

Michael Cardenas 1A wrote:Are N, O, and F the only atoms that hydrogen bonds can occur with or can they also occur with other electronegative atoms?

just N,O, and F since they are the most highly electronegative!

Kaiya_PT_1H

I think the other people are right, better to be safe than sorry and include (aq)!

Kaiya_PT_1H

Wait so is Br3- bromide or tribromide?

Kaiya_PT_1H

Was anyone else confused about this thread? for me, the first sapling question was a different formula.

Kaiya_PT_1H

When a question asks about whether hydrogen bonding is possible with a certain molecule, do they mean hydrogen bonding to itself or hydrogen bonding with water?

Kaiya_PT_1H

that diagram was a super helpful visualization, thanks Valerie!

Kaiya_PT_1H

conceptually, the "delocalized" part refers to the fact that in a molecule represented with resonance structures, the electrons actually form multiple bonds that don't correspond to the bond lengths of double or triple bonds. They basically go between the different areas that they would be...

Kaiya_PT_1H

I'm not 100% sure if this is actually true, but I think any molecule that has resonance structures has at least one delocalized pi bond! since resonance structures result from different combinations of multiple bonds and pi bonds are only present in double or triple bonds, that's what makes sense to...

Kaiya_PT_1H

Yes like Orla said, check with your major! I know in the spring a lot of majors allowed you to take classes P/NP even if it was a major requirement, but I don't think that's the case this quarter.

Kaiya_PT_1H

Yep I basically did the same as Jasmine, it seems logical to rule out answers that include "overwhelming" because the observed bond lengths seemed not to be super close to either the single or double bond lengths, but somewhere in the middle.

Kaiya_PT_1H

Yes I agree with Shamaya, the lower limit for a polar covalent bond is 0.5. The upper limit is around 1.6 or 1.7, and if the electronegativity difference is more than 2 it's considered to be an ionic bond!

Kaiya_PT_1H

I don't think triple bonds were being considered, but otherwise I agree with Kaihan! I think it's also logical to just rule out "overwhelmingly" since the observed bond lengths weren't clearly super close to a particular single or double bond length, if that makes sense.

Kaiya_PT_1H

Are there any other charts of trends that he mentioned? I guess all the information will be given to us but I'm just curious if I missed something.

Kaiya_PT_1H

I took AP chem 3 years ago and I remember having seen most of the topics so far, but I think Lavelle goes more in-depth with the explanations of why experiments were relevant and how they relate to the equations/concepts. Basically he gives more context for everything than we got in my AP chem class.

Kaiya_PT_1H

I've heard that it's easier if you take 14BL after 14B, but either way is possible. Personally, I'm hoping that in the spring they might offer some in-person labs for people in Westwood...

Kaiya_PT_1H

Are we doing respondus and zoom proctoring again? My TA said he thought that the easiest thing would be to have Respondus on your laptop and Zoom on another device (probably your phone) since some people had trouble getting into the Zoom call once they were in the lockdown browser. But he did say t...

Kaiya_PT_1H

I think for the post above, if you're using > to indicate one length is greater than another length, it would actually be single > double > triple since triple bonds are the shortest.

Kaiya_PT_1H

You can also do what Lavelle did last week in setting up a Lewis structure diagram by adding up all the valence electrons and the overall charge. In this case, carbon would have 4 valence electrons, each oxygen should have 6, and there should be two extra to result in the overall 2- charge. Therefor...

Kaiya_PT_1H

Will we be able to go over the midterms to see what questions we got wrong and what the correct answers were?

Kaiya_PT_1H

What is the difference between a shell and a sub-shell? And which is the orbital within? As Megan said above, shells include electrons with the same principal quantum number (n). I believe this could also be called the energy level. subshells are the different configurations within the shell, which...

Kaiya_PT_1H

I agree with what everyone said above, but also check to make sure it's not one of the two exceptions he talked about! The excited states of chromium and copper might look like what you would expect the ground state to look like (with the 4s orbital filled).

Kaiya_PT_1H

I noticed that there are a lot of textbook questions asking you to identify where a certain frequency or wavelength would fall on the electromagnetic spectrum (like whether it's UV, visible light, infrared, etc.). Is that something we need to memorize for the midterm?

Kaiya_PT_1H

okay cool, glad it's not just me! I think based on the range for microwaves it would make sense anyway, as Silvi said.

Kaiya_PT_1H

Does anyone else get an answer of the wavelength being 1 m? In the back of the book it says the answer is 1 nm but I don't see how I'm getting it wrong somehow.

Kaiya_PT_1H

Concerning calculators, you can use a variety of different ones. I personally use TI-84 CE calculator, but desmos also has a scientific calculator you can use. On Dr. Lavelle's website, he has a periodic table that you can use. Don't plan to use desmos on the test though! the respondus browser won'...

Kaiya_PT_1H

Hey I kind of have a similar question, but couldn't figure out how to make a new post. Does anyone know if there are answers to the questions in the textbook to check if we are doing them correctly? Yes, the end of the book has an "odd-numbered exercises" section where it lists all the an...

Kaiya_PT_1H

I think most of these problems have one solid component and one liquid component, so I would think the easiest way to figure out the solute/solvent in most problems would be to assume the solid being dissolved is the solute and the liquid it's being dissolved in is the solvent.

Kaiya_PT_1H

Why do we need to convert from g to moles here? Does the molarity equation need to have the compound in moles instead of grams? I just don't know the reasoning for needing moles. Thanks. We have to convert from grams to moles because the unit for molarity is moles per liter. The equation M = n/V us...

Kaiya_PT_1H

joshtully wrote:What is an amu? I understand that it is a unit for molecular mass, but what does it stand for?

amu means "atomic mass unit" which is a measurement based on the carbon atom: 1 amu = 1/12 the mass of an unbound carbon atom. https://www.thoughtco.com/definition-of ... amu-604366

Kaiya_PT_1H

I don't understand why a trailing zero isn't a significant figure. If 950000 is different from 950001, then shouldn't all the digits be significant figures? Perhaps I misunderstand the purpose of significant figures. 950000 only has 2 significant figures because it's only precise up to the ten thou...

Kaiya_PT_1H

Nan_Guan_3J wrote:I think it's because H only has 2 protons. and also, Hydrogen is not a very typical atom. although it's placed in the upper right corner on the periodic table, it doesn't follow some of the trends that apply to most other atoms.

Hydrogen actually has one proton, helium has 2 protons!

Kaiya_PT_1H

He also said in the lecture that the Lyman series emits waves in the ultraviolet range and the Balmer series emits waves in the visible light range. I'm not sure how relevant that is though.

Kaiya_PT_1H

I noticed in a previous lecture when prof was going over the equations like E=hv or c=λv the letter "v" was written with a bit of a curve. Is this intentional so we know that this V is referring to frequency and not velocity as it would in other equations, or is that just prof's handwriti...

Kaiya_PT_1H

Anyone have recommendations for STEM clubs to join that are active this fall? I know there are a lot of premed clubs, but I'd like to learn about more social-oriented clubs as well.

Kaiya_PT_1H

https://www.nytimes.com/2020/10/07/science/nobel-prize-chemistry-crispr.html https://www.cnn.com/2020/10/07/health/nobel-prize-2020-winner-chemistry-scn-intl/index.html For the first time in history, two women won the Nobel Prize in Chemistry (and didn't share it with a man)! They won the prize for ...

Kaiya_PT_1H

To add on to the previous replies, molar masses could also be adjusted to the level of accuracy that you need so that they don't interfere with calculations. If the source that you are using doesn't have the correct number of significant figures, and you think that it is a significant issue, you co...

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