CHEMISTRY COMMUNITY

SophiaJenny3I

Thank you so much everyone for your detailed explanations! This helps a lot :)

SophiaJenny3I

Hello everyone! So I was going through the textbook problems and got a bit tripped up on 4I7. Screen Shot 2021-03-12 at 10.08.20 AM.png Screen Shot 2021-03-12 at 10.08.13 AM.png In the problem, it has vaporization as having a -deltaH value, while melting is positive deltaH, is this not flipped? Shou...

SophiaJenny3I

Thank you so much! This did help :)

SophiaJenny3I

Hello everyone! Could someone please walk me through your reasoning for 4E9 in the textbook? I attached a picture below. Thank you!

SophiaJenny3I

Hi everyone! Hope everyone is doing well! Could someone please walk me through their logic for this problem? I don't know why I can't figure out some of the pH values given the information. Thank you!

SophiaJenny3I

Hi! My favorite show of all time is Psych, it's on Amazon Prime/Peacock. Highly recommend!!!

SophiaJenny3I

Hi! If I remember correctly from the Chem 14A final, everything is pretty equally allocated across the units. It's definitely cumulative, so definitely review older concepts!

SophiaJenny3I

Hi! I've been going to Justin's UA review sessions all quarter and they're super helpful! At 10-12PM on Thursday!

SophiaJenny3I

Hi everyone! I'm involved in Greek life, Cub Tours, and School on Wheels!!!

SophiaJenny3I

I would definitely redo the textbook problems. However, if you're worried you will be unable to work through them all, try to focus on the topics that have confused you in the past. If you really know concepts, don't spend too much time on those. Also, definitely go to UA review sessions because the...

SophiaJenny3I

Hi! DEFINITELY review all the units! Last time with 14A, I didn't review the past units as much as I should've so it took me longer to figure them out on the exam and I ran out of time. Highly recommend going through the textbook outline problems again, as well as attending as many UA workshops as p...

SophiaJenny3I

Hi! When I study for chem I love listening to Fleetwood Mac for some reason, it just puts me in a good mood :)

SophiaJenny3I

Hi! From what I learned with the 14A final, make sure to review everything!!! I had a false sense of comfort with the first unit we did and ended up struggling with problems from that topic. I plan on doing all the textbook outline problems again and redoing workshop problems I have attended in the ...

SophiaJenny3I

I agree with the comment above! Always make sure your voltage difference is positive!

SophiaJenny3I

I'm so glad that someone made this thread!!! I have so many favorite books, but I guess I'll just go with the one I'm currently reading that I love. It's called Sisters in Law and it's about Sandra Day O'Connor and RBG! It's a bit dense in terms of info at first, but really worth the read! Also, I l...

SophiaJenny3I

Hi! So, electrons flow from the oxidation half reaction (which gives off electrons) to the reduction half reaction (which gains electrons). In order to reduce the negative charge that this causes on the right (where the anions are), anions diffuse through the gel n the salt bridge and enter on the l...

SophiaJenny3I

Yes! You're allowed to go to any TA's office hours!

SophiaJenny3I

Hi! This is directly from my notes: "1 coulomb is the amount of electrical charge in 6.24 x 10^18 electrons." We just coulombs when discussing volts, as 1 joule of work/coulomb of charge transferred = 1 volt.

SophiaJenny3I

Hi! I think they count the number of posts based on your student ID number connected to your account. So I believe it shouldn't matter, but please correct me if I'm wrong.

SophiaJenny3I

Yes! Solids and liquids are ignored when calculating the equilibrium constant. This is because their respective concentrations essentially stay constant throughout the reaction.

SophiaJenny3I

I know this is such a typical answer, but my favorite food is pizza!!! Is anyone a fan of pineapple on pizza? I also love gnocchi, I've been making it in quarantine and it's a lot of fun!

SophiaJenny3I

Hi! I also didn't do as well as I wanted to on the final in 14A. I did all the textbook problems for the recent units, but I didn't re-visist the old textbook problems as much. That was definitely where I messed up. While I remembered the past problems to a certain extent, it wasn't as fresh in my m...

SophiaJenny3I

Yes the final is cumulative! One thing to note is to make sure you review past material as well (not just week 7-10). I made this mistake on the last final, and took way too much time on the actual exam trying to remember past concepts. While it's important to understand the current lessons, don't f...

SophiaJenny3I

Hi! Not necessarily. Always make sure you write out the units you have, and observe the unit you want and make sure everything else cancels out. This has helped me make sure I don't choose the wrong one! 8.314 is usually used when you want to end in J/kJ if you convert it.

SophiaJenny3I

My family had a pizza night so that was a nice way to destress :). I have another midterm I'm taking tomorrow, but after that I will really be able to de-stress!!!

SophiaJenny3I

Hi everyone! I was working through the textbook problems and got a bit tripped up on 4D9. I've attached a picture of the question below, does someone mind taking me through their logic? I understand you need to use enthalpies of formation, but I keep getting the wrong answer. Thank you!!! Screen Sho...

SophiaJenny3I

Hi! An abdiabatic system means there is no heat flow (q = 0). Therefore, in the equation deltaU = q+w --> deltaU = w because q = 0. Hope this helps!

SophiaJenny3I

Hi! I'm not sure if I remember that exactly. However, I think that statement means that the entropy of the universe is not going to favorably decrease. The universe favors disorder, not order (which would be caused by the decrease). Hopefully this is kind of close to what the statement means.

SophiaJenny3I

Hi! Residual entropy is also known as positional entropy. This correlates to the number of possible positions/states in a system. However, if there is only 1 possible unique state, the residual entropy is 0. One thing that's important to note is switching the orientation of a symmetrical model will ...

SophiaJenny3I

This has happened to me before! I just exit CCLE for a couple minutes or a half hour or so, then I come back and it normally works!

SophiaJenny3I

Hi everyone! There's a chance I might've missed this in an announcement or something, but does anyone know if there'll be UA sessions on Monday (holiday)? No worries if not, I just wanted to plan ahead! Thanks :)

SophiaJenny3I

A mistake that I've definitely made is focusing on the content that I'm pretty comfortable with. It's great you're being proactive!!! Just make sure you review the content you get wrong/are confused about sooner rather than later. While it's discouraging to review that content now, it'll help you la...

SophiaJenny3I

The UA sessions are SO helpful! I know Justin is doing a review on Thursday from 10AM-12PM (instead of the split up step up session and workshop). Highly recommend! I also like going through all the textbook problems on the outline. In reference to your other question, I think the module assessments...

SophiaJenny3I

I'll be using my first pass for Chem 14C! Personally, I want to do all I can to take these chem classes back to back!

SophiaJenny3I

I'm planning on take Chem 14C, Chem 14BL, and continuing my biotech cluster!

SophiaJenny3I

Hi! Definitely just focus on what is given in the problem. It can be either Kelvin or Celsius, but both temperature values have to both be in kelvin and celsius in order to make sure the change in temp is accurate. I always like to write everything out so I avoid any silly mistakes!

SophiaJenny3I

The workshops are SUCH a great resource. The UAs are all super helpful and have so many problems to go through. What's great about them is, not only do you set aside time to work on chemistry outside of lecture/textbook problems, but you can use these problems to review later! Before an exam, I go t...

SophiaJenny3I

In an isolated system, nothing exchanges with the surroundings. So, you can't change the energy as you can't add/remove a certain amount of substance, heat/cool the system, do work on it, etc. Hope this helps!

SophiaJenny3I

Hello! I think all you need to focus on with closed systems is "stuff" can't go in and out. Only energy can exchange with the surroundings, and it can also be heated. However, I remember in lecture that one of the ways we can change the energy of a closed system is to do work (such as comp...

SophiaJenny3I

Ryan Laureano 3I wrote:I actually remembered a quick trick for gibbs free energy. delta g = -RTlnK or ratlink
This may or may not help but its good to know.

I use this one too!!! It's always helped me remember it, even as silly as it may sound!

SophiaJenny3I

I can definitely relate to this! Just focus on taking your time, especially on an exam. If you don't know a problem, skip it so you don't rush through the ones you know. I normally try to leave time to go back and quickly redo the problems to a certain extent, or at least go back through my work aga...

SophiaJenny3I

Hi! I love doing as many practice problems as I can. I aim to go through all the textbook problems before the exam, because they're such a good barometer for what we need to know. Also, go to workshops each week! It's a good way to stay on top of the material and challenge yourself! Also, they make ...

SophiaJenny3I

Hi! When I have a lot of tasks to accomplish/complete, I love to make a list! While a list seems daunting, they are smaller, tangible ways for you to feel accomplished. I use Notes on my computer to make a checklist, and when I complete a task, I click on the bubble and it puts a little checkmark by...

SophiaJenny3I

Hi! Just remember that forming bonds is exothermic (the release of energy), while breaking bonds is endothermic (takes up/requires energy)! When thinking about the effect of a temperature change, I like to think about it like this: for exothermic reactions, the deltaH is negative. If the temperature...

SophiaJenny3I

Hi! Next quarter I plan on taking 14C and 14BL! I definitely want to keep all the chem classes together so the concepts stay fresh in my mind and it's a nice progression through the material.

SophiaJenny3I

I love to go on walks once a day to relax! It definitely helps clear my mind and allows me to be slightly active! I also love to read a good book or just watch some Netflix :)

SophiaJenny3I

Hi! It's the amount of posts. Also, asking questions count towards the number of posts/week! Definitely focus on doing the 5 posts/week.

SophiaJenny3I

Oh my goodness! ^I absolutely LOVE Psych! I can't believe Taylor K said that, I've met very few people who know about Psych. I cannot recommend it enough!!! My other favorites are Schitt's Creek, Young and Hungry, The Office, How I Met Your Mother, and The Crown. I LOVE PSYCH!!! I feel like no one'...

SophiaJenny3I

Hi! You just have to look at the units the problem gives you. Normally, it's deciding between the one with bar and atm, and the problem will tell you which to use! If you're ever uncertain, write out all the units when you're calculating a value using R and double check that the units cancel and you...

SophiaJenny3I

Hi! When you're thinking about the effect of pressure on a system, you need to focus on the volume. When an inert gas is added, it doesn't change the volume. It's non-reactive and doesn't affect the concentrations of the molecules in the system.

SophiaJenny3I

Hi! To take the antilog of something (whether it be to go from pH ==> [H30+], pOH ==> [OH-], pKa ==> Ka, etc.) you just take that number and make it the negative power of 10.
For example: pH = 6 --> 10^-6 --> 1 x 10^-6. Hope this helps!

SophiaJenny3I

Here's the link: https://lavelle.chem.ucla.edu/wp-conten ... dterm1.pdf
It explains everything and is super helpful :)

SophiaJenny3I

Hi everyone! Just wanted to confirm the difference between amphoteric and amphiprotic. Amphiprotic means a molecule can ACT as both a proton donor and proton acceptor (using the Bronsted definition of acids and bases), while amphoteric means a molecule can REACT with both acids and bases. Is this co...

SophiaJenny3I

Hi! You're correct you do have to find the kB value first. This is because you're specifically looking for the pH of the salt NaClO, which is identified in the problem as a weak base. So yes, you have to convert to Kb from Ka!

SophiaJenny3I

I'm pretty sure last time there was an extra five minutes or so just in case. However, don't be concerned. When I took the first midterm in 14A, my Respondus lockdown browser glitched and crashed my computer so I had to borrow my mom's and download it. That took a solid five minutes but once I click...

SophiaJenny3I

Hi! If the K value is < 10^-4 we can use the approximation that the amount of x is very small relative to the initial concentration. Therefore, the difference between the initial and the change is just the initial. It's important to understand that x is NOT zero, but insignificant to the change in i...

SophiaJenny3I

Hi! Yes, since H20 is in its gas form, we include it in the equilibrium constant. For equilibrium constants, we use concentrations of aqueous solutions and gases. We exclude solids and liquids (that are often solvents, in the case of water). H20 in its liquid form is omitted because the change in so...

SophiaJenny3I

Hi! The UA sessions are SUPER helpful. Definitely recommend those. Also, going through all the textbook problems in the outlines! They're great practice. I like to read the textbook sessions as well and take down some main notes, just so I know I have the concepts down! If I have time, I also like t...

SophiaJenny3I

Yes I agree. I would assume it's safe to say that if the word problem says it is oxygen gas, that it's diatomic as that's it's structure. Same with the other diatomic gases: nitrogen, fluorine, hydrogen, and chlorine.

SophiaJenny3I

Hi! An inert gas is basically a gas that won't react with anything in the reaction. The system does not respond to the inert gas because while the pressure goes up, the volume is NOT changing. And that's the key element. The reaction staying in equilibrium is dependent on the concentrations. The con...

SophiaJenny3I

Hi! I typically read the textbook go through all the extra problems from the outlines. They are super helpful and are great at pointing out concepts that I'm shaky on. The workshop sessions held by the UAs are super helpful as well! I like to go over those problems and redo them before the midterm. ...

SophiaJenny3I

Hi! You just have to look at what's given to you. Since in #10 you are given both initial concentration, plug those into the ICE table and work from there. I've found that these problems make a lot more sense when you write out everything you know, and then begin to fill in the blanks to figure out ...

SophiaJenny3I

Often when you get the question wrong, a feedback note pops up! These can be super helpful and really can walk you through the problem. Definitely don't click "I give up" as I'm pretty sure you won't get credit, and it's definitely not worth it! Try the feedback from the different answers ...

SophiaJenny3I

I love watching any Star Wars movie. For a fun silly one, I love Despicable Me!

SophiaJenny3I

Hi! During 14A I would typically read the textbook section and immediately do the problems following it to help keep me on track. I typically did the textbook problems a couple days after it was taught in lecture, and gradually caught up as I approached the midterm. My goal was to finish the majorit...

SophiaJenny3I

Hi! So basically (aq) stands for aqueous which basically means the substance is dissolved in water. (l) stands for liquid and that means the substance is in it's pure liquid state. We don't include H20 when calculating the equilibrium constant because it's a pure substance. The molar concentration o...

SophiaJenny3I

Hi! Thermodynamics hasn't been covered in-depth yet so I wouldn't worry too much about it. Probably understanding endothermic/exothermic reactions for now is perfect. If you look ahead to the outlines, we will be covering it in Outline 4! Hope this helps!

SophiaJenny3I

Just remember that hydronium concentration [H30+] is related to pH and hydroxide concentration [OH-] is related to pOH. So, since you're given the pH, you need to convert to pOH. You do this by using the equation 14 = pH + pOH. Rearrange the equation to solve for pOH: pOH = 14-pH. Then, once you hav...

SophiaJenny3I

Yes! It tells you to refer to them, as you need the Ka values to solve this problem!

SophiaJenny3I

Yes! It all means the same thing. Dr. Lavelle has mentioned he doesn't prefer the "shifting" term just because it's misleading, since equilibrium doesn't shift. However, they're all right and the same thing! And yes, when the forward is favored, the reaction favors the products because the...

SophiaJenny3I

Yes! It all means the same thing. Dr. Lavelle has emphasized however that the equilibrium "shifting" is a misleading description since the equilibrium doesn't shift, it just favors the reactants. But, they're all correct!

SophiaJenny3I

I'm pretty sure it's just for equilibrium, since last quarter we only had them for the beginning to make sure we all were on the same page at the start of the course.

SophiaJenny3I

Hi! So, in the PV = nRT equation, here are what all the variables represent which will help. P = pressure in atm, V = volume in L, n = moles, R = gas constant ( 8.206 x 10-2 L·atm·K-1·mol-1, for example), and T = temperature in K. Most important thing about figuring this out, is understanding Molari...

SophiaJenny3I

Hi! I've found that my biggest problem with studying is I never spend enough time on the stuff I'm shaky on. I like going through concepts I know how to do, just to confirm I do, but it ends up taking way too much time. While it can be daunting to do practice problems on concepts you don't like/find...

SophiaJenny3I

Hi! The UA sessions are super helpful! We always go over some practice problems, so they're awesome when you're reviewing later on for the midterms. Also, it's a good chance to check what you know and see what you're a bit shaky on. The textbook problems in the unit outlines are a lifesaver, and rea...

SophiaJenny3I

Yes I definitely ran out of time too. I caught myself obsessing over problems that I wasn't sure about, so I was rushing at the end. I've definitely learned my lesson from that and hopefully can take that lesson into 14B! We got this guys! :)

SophiaJenny3I

Hi guys! Could someone please clarify the differences between hard and soft water? Thank you!

SophiaJenny3I

Whenever I'm struggling with a topic, I like to reword the conceptual ideas and write them down in my own words. This forces me to identify what I'm confused about. Also, I like doing a lot of practice problems, especially from this textbook. If you are having trouble, it's ok to look at the key and...

SophiaJenny3I

Please post the entire question for other people to reference. But for the logic of this problem, the most significant Lewis structure of a molecule is the one with the smallest net formal charges, in other words, the lewis structure where the formal charges are closest to 0. Thank you so much! Thi...

SophiaJenny3I

Hi! Definitely choose something you're passionate about. This will help motivate you in the future and make you love what you do! Think about what makes you happy. Do you love to write? Ask inquisitive questions and interview people? Analyze movies and TV shows? Play an instrument? Is there a partic...

SophiaJenny3I

There will definitely be some from the textbook. Make sure to review quantum specifically since that was the most time we spent on a section!

SophiaJenny3I

Jade_Tai_2L wrote:I only remember Dr. Lavelle going over Cisplatin-- do we have to know others?

I'm pretty sure the only one we'd have to know is cisplatin, and possibly why transplatin is its ineffective counterpart.

SophiaJenny3I

Hey guys! Could someone please explain their logic to determining the most "important" Lewis structure in this problem? I circled this one and came back to it but I'm still a bit confused. Thanks in advance!

SophiaJenny3I

I am almost certain that Dr. Lavelle said in lecture we don't need to know which is which, it's just a matter of knowing the different properties and how/when pi bonds exist!

SophiaJenny3I

What's a chemist's favorite dog?
A Laboratory retriever! :)

SophiaJenny3I

Hi! en is shorthand for ethylenediamine (H2NCH2CH2NH2). It's a bidentate ligand, so when it's in a complex it contributes two to the coordination number. Hope this helps!

SophiaJenny3I

Hi! This is more in general for coordination compounds, but here's a resource that has been super helpful that is on Dr. Lavelle's website: https://lavelle.chem.ucla.edu/wp-conten ... pounds.pdf
Hope this helps!

SophiaJenny3I

Hi! So here's some of the main points I've gathered about resonance. One thing that's important to remember is that a molecule with resonance doesn't change between these different structures. A resonance hybrid is a merging of structures. In addition, the electrons in the different positions are de...

SophiaJenny3I

Definitely go to all the review sessions you can that Dr. Lavelle has set up. The UA workshops have been such a great resource for me, and provide even more practice problems for the future. Also, I catch myself doing this a lot so don't just practice the stuff you know. It's super easy and comforta...

SophiaJenny3I

I'm good! Getting so excited for Christmas and break! Definitely a bit nervous for all the finals though.

SophiaJenny3I

Darren1e wrote:By studying homework problems, are you referencing sapling or the textbook?

I think mainly focus on the textbook problems, but it wouldn't hurt to give the Sapling ones a glance!

SophiaJenny3I

Hi! In the Week 10: Final Review Sessions document it describes how the material will be weighted. "Final covers all material (approximately weighted to the amount of time covered in the syllabus). Quantum was the biggest section." Hope this helps clarify!

SophiaJenny3I

Hi! So a pi bond only happens in double and triple bonds. If there is a double bond, it is one sigma bond and one pi bond. If there is a triple bond, it is one sigma bond and TWO pi bonds. You can't rotate pi bonds because they are parallel side by side and that would break the bond. The sigma bond ...

SophiaJenny3I

Hi! This question confused me a bit as well, but once I figured it out I clicked on the "solution" button on the homework for that question and the explanation was great! Here it is: "Resonance structures are multiple Lewis structures that collectively represent a molecule. Resonance ...

SophiaJenny3I

I'll make sure I get through all the textbook problems for this unit, and then go back and review all the Sapling homework for a good outline of problems. I'll also go back and do most of the textbook problems from previous units if I can, and go through workshop problems.

SophiaJenny3I

Hi! So the lone pairs actually repel the bonding regions. There is more repulsion between a lone pair and a bonding region, rather than a bonding region with a bonding region. Therefore, the lone pair repels the bonding region, and it goes closer to the other bonding region. This is what makes the a...

SophiaJenny3I

Hi! So any orbital, as well as a d orbital, can only hold a max of 2 electrons and these electrons must have opposite spins. If you're a visual person, it helps to look at the periodic table. The d subshells are basically represented by the transition metals. Each row of transition metals has 10 ele...

SophiaJenny3I

Hi! A molecule has delocalized pi bonds when it has resonance with double or triple bonds. So, think about what has the capacity to double bond or triple bond in the first place, and if these double or triple bonds can be "moved" around.

SophiaJenny3I

Hi! So degenerate orbitals are orbitals with the same energy. When the the value of n and l is the same, they are degenerate orbitals. For example, in the 2p subshell, there are 3 degenerate orbitals. The only exception to degenerate orbitals is when the same value of n has DIFFERENT values of l in ...

SophiaJenny3I

Hi! Here's the link to Dr. Lavelle's sig fig cheat sheet you can find on his website.
https://lavelle.chem.ucla.edu/wp-conten ... OUT_SF.pdf

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