CHEMISTRY COMMUNITY

Breanna Ouyang 1I

I think the difficulty is actually pretty comparable! It just takes longer since you have to keep going through for like double the amount of questions during the final. Last quarter I think a lot of people thought the final was a lot harder, but I thought the level of difficulty was somewhat expect...

Breanna Ouyang 1I

Do you know what I can search to find that thread?? There's 2 threads as of now I think titled "Advice from a Medical Student" and it's endorsed by Lavelle/chem_mod, so you can find it through the board index under Admin related questions. Here's the link to part 2: https://lavelle.chem.u...

Breanna Ouyang 1I

Thank you! Just trying to push through another week to end strong so all that work finally shows through :)

Breanna Ouyang 1I

Jonathan/s right! You just figure out which integrated rate law you need to use for the problem (this can usually be deduced from the units given, but we know it's first order here) and just plug and chug.

Breanna Ouyang 1I

That's probably most likely. I'm not sure how else he would format it but each of the 6 outlines were pretty evenly spaced/distributed for 14B anyway

Breanna Ouyang 1I

I wouldn't worry too much, it's usually up by mid week and probably will be due end of week 10 (and, if not, will be due end of this week but shortened)

Breanna Ouyang 1I

The previous replies are right! Essentially just look at the balanced redox reaction and the concentrations given in the question.

Breanna Ouyang 1I

I'm considering pre-med but it's a long process a lot of people drop lol. There's an active thread on here with a med student who answers a bunch of questions and gives advice, so I'd check that out!

Breanna Ouyang 1I

All the previous replies got it! The stoichiometric coefficient in a balanced redox reaction for e- is in terms of moles, so 3e- is 3 moles of e-.

Breanna Ouyang 1I

Just finished the Queen's Gambit and would highly recommend!

Breanna Ouyang 1I

The addition of thermal energy and thermal motion makes it so the molecules move around faster and can occupy more possible states. It's a little intuitive.

Breanna Ouyang 1I

For me, I just understand that the oxidizing agent causes another substance to be oxidized and the reducing agent causes another substance to be reduced.

Breanna Ouyang 1I

For the purposes of this class we just assume they are lol

Breanna Ouyang 1I

Not my fave food but definitely craving a pulled pork sandwich right now

Breanna Ouyang 1I

What Edward said, but also the first step is to thik of them as half reactions and figure out their changes in oxidation number so you ca better figure it out.

Breanna Ouyang 1I

It's to account for the different steps in the process: the melting of the ice and the heating of the ice

Breanna Ouyang 1I

I'm planning on taking BL next quarter/spring with 14c. I know others are starting the Physics 5 series, but I'm first passing BL and C together.

Breanna Ouyang 1I

Your approach is right! You might've made a small calculation error somewhere, but your answer should be approximately -662 kJ after solving based on the info you gave (the second equation is reversed and doubled for enthalpy and entropy while the first equation stays the same). I could be wrong tho...

Breanna Ouyang 1I

Yeah, Lavelle only teaches the gen chem series. Orgo has many different professors associated with it but 14A and B are just Lavelle and Scerri.

Breanna Ouyang 1I

You can usually figure out which R to use based on the units you're using to solve. If you're using PV=nRT, then it involves pressure and would need the R that includes atm, but you use 8.314 in other cases. It's easier to write out you process and all units so you know what cancels out where.

Breanna Ouyang 1I

I read a fantasy book or pet my cat in my free time. Either that or play games in VR lol

Breanna Ouyang 1I

Was there a minor calculation error? I tried it and got -507.3 from (2*109.3) - ((3*223.1)+(2*28.3)), but that might be wrong lol (your process is right though)

Breanna Ouyang 1I

Tests are never curved with Lavelle, but for the 14a final he did give everyone an extra 10 points. I don't think he'd be so nice after midterm 1 though since like 20% of the class aced it.

Breanna Ouyang 1I

Criminal Minds has been my comfort show over quarantine but I've been starting Gilmore Girls recently for the first time. Favorite show is Haikyuu though :) (lol)

Breanna Ouyang 1I

I would say that, after Lavelle finishes each section/outline, try to go through the homework textbook problems to have a good grasp on the problem solving, and then when midterm season comes around review those textbook sets. The UA sessions are also really helpful.

Breanna Ouyang 1I

Everyone above is right! Negative heat capacities can't exist because they're the amount of heat put into the system to create a 1 degree raise in temp.

Breanna Ouyang 1I

Try writing everything out! I sometimes do the same thing and make mistakes over and over again, so I've tried to make it a habit to write down all the important numbers. On exams I just try to do every question 2 or 3 times to confirm I'm right.

Breanna Ouyang 1I

I usually spend a little under 10 hours a week outside of lectures. I try to attend 2 UA sessions a week and, alongside that, there's sapling homeworks. I catch up on the assigned homework problems by the end of each week for the material he covered and it all comes to about 10 hours. I don't do muc...

Breanna Ouyang 1I

Hi Anil! One thing that might help if to do your work after classes outside of your bedroom! Maybe in your living room or kitchen, just to be around lively people maybe, but that does sometimes distract you more lol. I try to take a break every couple of hours to maybe relax and pet my cat, but it's...

Breanna Ouyang 1I

When steam touches your skin and condenses, it undergoes the phase change that releases a lot of thermal energy, all of which severely burns your skin more than boiling water would since that phase change difference is not experienced.

Breanna Ouyang 1I

I took 14a with Lavelle online last quarter and all his exams were multiple choice. Out of the 3 exams, only 1 had partial credit and the other 2 were all or nothing. They usually didn't tend to be multipart (each mcq was independent from another), so if you got one question wrong it was unlikely to...

Breanna Ouyang 1I

It's because of the molar ratio, Ashlen's right. Every mole of Ba(OH)2 produces 1 mole of Ba2+ and 2 for hydroxide ions when it dissociates.

Breanna Ouyang 1I

There's no way really. You can access test banks through certain clubs and student orgs maybe if you can't ask upperclassmen. There's also past practice question sets for the course on chemistry community from past years when the UAs did joint exam review sessions, so those can help!

Breanna Ouyang 1I

They're using the formula MiVi=MfVf to find the molarity in part b (to find the pH) instead of just using concentration=moles/V.

Breanna Ouyang 1I

All the UAs make their own worksheets! I would recommend Michael Nguyen because he has his own drive of worksheets with answer keys attached. All the other UAs are really good too. Depending on their time slot during the week the UAs might cover more recent material or material from the previous week.

Breanna Ouyang 1I

Yeah it is! It's not really covered in 14B because it was 14A material from the introductory Acids and Bases section, so it's more basic conceptual ideas on pH versus pKa.

Breanna Ouyang 1I

emmaferry2D wrote: thank you this does help! I just wasnt sure if there was a way to figure out this problem without using the table !

Yeah for all questions like these we need given Ka or Kb values in the problem! You can't solve for them with just molar concentrations.

Breanna Ouyang 1I

Multiple attempts are all good. I knew someone who used 40+ attempts on one question! Hints are fine too, just don't give up on any. They're graded only for completion.

Breanna Ouyang 1I

This question is working backwards in a way. After being given the pH, you then find the pOH and the molar concentration of OH- ions (which is x in the ICE table). I think you then use that value to find the initial concentration of the amine and divide x by it for percent protonation.

Breanna Ouyang 1I

Yep, Hannah's right! You would use Kw (10^-14) and the Ka or Kb value given to find the Ka or Kb for the compound you're given, depending on if it's a conjugate acid or base in the reaction.

Breanna Ouyang 1I

What's a sign of a bad chemistry joke?
No reaction :/

Breanna Ouyang 1I

Chloe's right! Concentration (molarity) = moles of solute/volume, so 1.5 moles is divided by the 0.5 L of the reaction vessel to find the concentration used in the problem.

Breanna Ouyang 1I

I'd definitely try to email your TA or Lavelle about it, I'm not sure if this is a common problem if you've exhausted all known options

Breanna Ouyang 1I

The equation comes out to be 2A -> 1B + 2C. This is because A and C change by about 10 kPa when B only changes by 5 kPa (this is how you get the mole ratio). You would then use the equilibrium partial pressures and plug it into Kc = [B][C]^2/[A]^2

Breanna Ouyang 1I

I'd say Tangled and To All the Boys I've Loved Before are comfort movies of mine! If not those then probably some 2000's DCOMs

Breanna Ouyang 1I

The answer is C because it's at dynamic equilibrium (not static equilibrium), so the reactions are just occurring at equal rates.

Breanna Ouyang 1I

Ashlen basically covered the explanation! I was a little confused because I wasn't sure which side of the reaction the volume was changed on, but as clarified above, the equilibrium shifts to the product side since there are less moles there. Since the deltaH value is negative, the reaction is deter...

Breanna Ouyang 1I

I agree with Vivian! The equilibrium constant tells us about the concentrations of products and reactants because we are already aware that, at equilibrium, the forward and reverse reaction rates are equal

Breanna Ouyang 1I

The answer is no because liquids/solvents do not experience significant change in concentration!

Breanna Ouyang 1I

Yasmina's right! The concentrations of the reactants and products at equilibrium are not necessarily the same, only that the rates of the forward and reverse reactions are.

Breanna Ouyang 1I

If the salt has the cation of a strong base and the anion of a strong acid, then the salt is neutral (We'd just refer to the strong acids and strong bases list we have to memorize). If there is the cation of a strong base, but the anion of a weak acid, the solution is basic. If there's an anion of a...

Breanna Ouyang 1I

I'd say yes? I think we're working under the assumption that H+ acts as the proton.

Breanna Ouyang 1I

To generally identify am amphoteric compound, it should have a hydrogen present in the formula and a negative charge so that it can act as both an acid and base. Not sure if we have to memorize the list, but it would probably help a lot.

Breanna Ouyang 1I

I think so? Pretty sure we should make sure we're able to recognize ethylenediamine and such ligands with their corresponding formulas and names.

Breanna Ouyang 1I

I think Katarina is right. I think order/alphabetical order only matters really for naming.

Breanna Ouyang 1I

Heisenberg was cruising down the highway one day when he gets pulled over by a police officer. The officer gets out of his car, and Heisenberg can tell he's quite angry. The officer approaches the window fuming. "Do you have any idea how fast you were going?!" the officer asks. "No&qu...

Breanna Ouyang 1I

It's probably better to know those, but also probably better do just do enough practice problems and look at enough compounds (and names of compounds) so that you internalize them without having to outright memorize them.

Breanna Ouyang 1I

Same! Aiming for an A but worried for how the final will go... I wonder if he does any grade adjustments at the end of the quarter.

Breanna Ouyang 1I

Do the textbook problems and the UA worksheets! I sometimes like to brush up on content review by rereading my notes because rewatching lectures is a bit too much. The sapling questions aren't as helpful as the ones straight from the textbook and the past midterm questions the UAs put on their works...

Breanna Ouyang 1I

Maybe try typing it differently? I was having a similar problem and if your answer is tetra ammine chloro cobalt (II) chloride, type it in as tetraamminechlorocobalt(II) chloride because the anion is outside and technically separate. It might also be dichloro

Breanna Ouyang 1I

E=hv is used to find the energy of a single photon of light when it interacts with a single electron. The DeBroglie equation is used to find the wavelength/wavelike properties of objects, but they could be used together in a problem as mentioned above.

Breanna Ouyang 1I

Yep, what Katarina said was right! In a tetrahedral shaped molecule, none of the bonds are directly across from each other (so the C-H and C-Cl bonds aren't directly across) and their dipole moments don't cancel, making it polar.

Breanna Ouyang 1I

Same here!! It was question 17 for my sapling, but for the 3 structures of C3H4, none were resonance structures of each other

Breanna Ouyang 1I

I usually go out for a walk around my neighborhood for some air or bike around, but it's been getting a little cold where I am for that now

Breanna Ouyang 1I

Not sure exactly what you mean, but generally I'd say yes? Depends on what the Lewis structure looks like

Breanna Ouyang 1I

I agree with Stuti! Both CHI3 and CHF3 are nonpolar molecules, which means the only intermolecular forces they experiences are LDFs. Once you know that, you figure out which of Iodine vs Fluorine is larger in size (and thereby more polarizable) to see which molecule has the stronger LDFs.

Breanna Ouyang 1I

There might be a potential conflict because Lavelle said he isn't sure if he can have chem 14b winter quarter be asynchronous/recorded. If it does end up asynchronous you should be good to go though.

Breanna Ouyang 1I

When CCl4 has a higher boiling point because of its size is Lavelle referring to its London dispersion forces? When you increase size (or molar mass) polarizability increases, and so the attractive LDFs increase in strength and thereby make the boiling point higher. Questions about boiling and melti...

Breanna Ouyang 1I

I agree with Rich! A radical just means there's an unpaired electron left in the compound, so if you count up all the valence electrons of atoms included in a compound and it's an odd number, chances are it's a radical. It would probably be in a question asking about highly reactive substances or re...

Breanna Ouyang 1I

Yeah, you can definitely take it later! Some people decide to take it the quarter after 14B with 14C or they take BL alone and take C later on!

Breanna Ouyang 1I

Probably my number 1 tip would be don't do your work in bed. Carve out your own separate workspace so that your brain can easily distinguish where you go to bed and where you feel focused, since laying in bed can make you 1. really sleepy and 2. distracted. Personally, I always list out all my assig...

Breanna Ouyang 1I

The number of orbitals is dependent on the subshell, so if a) is l=2, that means it corresponds to the d subshell. The d subshell has 5 orbitals (-2, -1, 0, 1, 2). Generally, to find those numbers, it follows this rule: -l<m l <l Accordingly, l=0: corresponds to s subshell -> 1 orbital l=1: p subshe...

Breanna Ouyang 1I

I agree with Marc! One thing I think a UA stressed was that some atoms are better at holding a negative formal charge, particularly oxygen, so, in the case you presented, it might end up being more stable for oxygen to have a -2 formal charge instead of all atoms having a FC of -1.

Breanna Ouyang 1I

Possibly, but there might be a little more since the topics are less math-y. I did hear people talking about this upcoming exam having more questions so it's not as easy to lose points, but not totally sure.

Breanna Ouyang 1I

I'm in the same boat too :// didn't do bad on the first midterm, but we still have 2 big tests coming up we can't lose over 30 points on, and I feel less prepared for midterm 2... I try not to think too much about it but if I ever want to predict my grade for the class I just go on the syllabus to c...

Breanna Ouyang 1I

Honestly I think keeping up with lectures, doing the sapling problems, and attending workshops help me best. The textbook readings don't help much and the textbook questions too. Going through full practice problems during workshops help a lot more and the homework problems feel more comprehensive t...

Breanna Ouyang 1I

Yea, Dr. Lavelle commented a few days ago on someone's post saying that one of the questions had an error, so each test will need to be looked over by a TA this week. He said "it will take a while," so they'll probably be out in a few days. Do you know if everyone's test had an error? Or ...

Breanna Ouyang 1I

I think someone mentioned it should be up within the next day, but definitely within the next couple of days

Breanna Ouyang 1I

Yep it's 10 and not 5! There was an earlier post or correction clarifying that the solutions manual has the wrong answer

Breanna Ouyang 1I

This is so amazing! Do you have any advice for first years who are just starting out looking for opportunities/ways to get involved?

Breanna Ouyang 1I

All the questions from the fundamentals section and all the questions in focus 1A and 1B

Breanna Ouyang 1I

Okay, so I found frequency based on wavelength and made sure to convert that to meters from nanometers beforehand. I got 6.17 x10^-4 for frequency. I plugged that in as well as Rydberg's constant (3.28984x10^15 Hz) and (1/2^2-1/x^2). I divided frequency by the constant and got 1.875x10^-19. I subtr...

Breanna Ouyang 1I

Nope! The only part of 1D to know is the conceptual background of Schrodinger's Wave Equation. You don't need to know how to do the section's practice problems really.

Breanna Ouyang 1I

Ryan Hoang 1D wrote:What do you get when you mix some carbon, oxygen, and a little bit of heat?

My house.

(I'm from Irvine during the Silverado fire).

Sorry to say this made me laugh out loud

Breanna Ouyang 1I

A photon checks into a hotel, and the desk clerk asks, "Have you any luggage?"
To which the photon replies, "No, I'm travelling light."

Breanna Ouyang 1I

Hello, Dr. Lavelle has emphasized that there will not be much material on this upcoming midterm and there are 102 hours of assistance outside of lecture for students to prepare for the upcoming midterm. That being said, he does not see the need to have any midterm review sessions. However, please a...

Breanna Ouyang 1I

The absorption spectrum shows the wavelength of energy absorbed by the electron as it is excited to a higher energy level. The emission spectrum records the detected wavelength of energy emitted by the electron as it returns to a lower energy level. Both wavelengths are of the same value, just diffe...

Breanna Ouyang 1I

I remember last week in one of UA Kate Santoro's workshops that she did a joint workshop with UA Matthew Tran for midterm review. Has anyone heard any news about that or know when we'll be able to access the review materials/be working on it?

Breanna Ouyang 1I

Since the q specifies the ultraviolet region, you know the final energy level is n=1 (Lyman series). For the overall problem you would use deltaE=Ef-Ei. Since you know the final energy level, use Ef=-hR/n^2 to find Ef, and then use E=hc/lambda to find deltaE. Plug those values into deltaE=Ef-Ei to f...

Breanna Ouyang 1I

What's the difference between a seal and a sea lion? An electron

Breanna Ouyang 1I

The question asks "How many orbitals can have the following quantum numbers in an atom: (a) n=2,l=1; (b) n=4,l=2,ml=−2; (c) n=2; (d) n=3,l=2,ml=+1?"

Can someone explain why the answers are 3, 1, 4, and 1, respectively?

Breanna Ouyang 1I

What did the scientist say when he found 2 isotopes of Helium?
HeHe

Breanna Ouyang 1I

Saineha was right! You have to further divide by Avogadro's number to figure out the amount of energy required to remove an electron for a single sodium atom. I think the work function given only tells you how much energy is required for a mol.

Breanna Ouyang 1I

"In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that leads to this spectral line." I know that since it's observed in the UV range that it's part...

Breanna Ouyang 1I

I'd agree with John! Our SI units we use don't go smaller than 1 picometer (10^-12), so anything smaller you could consider undetectable. The undetectable values in the worked examples were like 1.0 x 10^-38, so questions probably won't be too ambiguous on that

Breanna Ouyang 1I

The link for Disc 1C is https://groupme.com/join_group/63069511/nhIo7EcW

Breanna Ouyang 1I

KatarinaReid_1B wrote:So far, my TA for Dis 1B let us know that we would have a practice quiz not for a grade to practice using Respondus, a program we will be using during test, this week.

Hi! Did your TA give any indication as to how many quizzes we would have/how often?

Breanna Ouyang 1I

So those classical objects are particles, and the module discusses how electrons, in the referenced experiment, act as waves and not as particles. Particles would pass through the holes in the barrier, while waves would not pass through the barrier, but would interact with each other, constructively...

Breanna Ouyang 1I

I'm pretty sure most formulas and constants will be given to us for tests, but it might be helpful just to keep them in the back of your head.

Breanna Ouyang 1I

I think the exams are free response (my NSA during orientation gave us a glimpse into her old test banks). I'm not sure if they include any multiple choice though, sorry! Not sure how they'd proctor us, but I heard they'll be using a type of lockdown browser along with Zoom?

Search found 102 matches