CHEMISTRY COMMUNITY

Zainab Jamali 1H

boost!!! also i didn’t thank my classmates on my slide but you all have been amazing and such a supportive group, thank you so much!! :)

Zainab Jamali 1H

pay attention to the units of the given values! if it’s multiple choice look at the units of the answer to give you an extra hint :)

Zainab Jamali 1H

this thread is amazing!! i honestly would love to have access to dr. lavelle’s playlist he has very good taste in jam-worthy music haha

Zainab Jamali 1H

for me, it helps to have a designated study space so that i don’t feel overwhelmed and i can get away from studying completely when i need a break! also taking walks as study breaks instead of just going on my phone (which i’m guilty of) and it really gives my brain like a power nap! good luck :)

Zainab Jamali 1H

just as an FYI if you're struggling with electrochem and/or kinetics, there's a great worksheet on chemistry community to review tougher concepts in those sections! just search "endgame" and there should be a thread that has the pdf!! it helped me a lot :) good luck on the final everyone!!...

Zainab Jamali 1H

I had the same question! Thank you for asking :)

Zainab Jamali 1H

These are the main conversions we learned in class!
Ka*Kb=Kw
pKa+pKb=pKw
Kw=[OH-][H+]= 1x10^-14
also for buffer systems only, you can use the henderson-hasselbach equation to convert from pKa to pH.
hope this helps!

Zainab Jamali 1H

organic chemistry tutor helped me a lot with understanding the basics of electrochemistry! the only thing is those videos can be kind of long so not ideal if you are trying to study in a short period of time (which has happened to me before haha)! if that's the case, you can always try 1.5 or 2x spe...

Zainab Jamali 1H

for this class, i definitely prefer handwriting my notes! the only time I type notes is when I feel like I will struggle to keep up with the lecture while taking notes by hand. for this class, given that it is recorded, I am able to pause at points if I need to so taking notes by hand is not stressf...

Zainab Jamali 1H

so excited!! thanks for organizing this :))

Zainab Jamali 1H

The salt bridge prevents ion build-up on either side of the galvanic cell and helps maintain a neutral charge as electrons flow between the two sides.

Zainab Jamali 1H

The ln equation applies in all cases but the log equation can only be used for reactions at 25 degrees Celsius (or 298K).

Zainab Jamali 1H

The oxidizing agent encourages oxidation of the other species by being reduced itself, so yes, you would be correct in saying that the oxidizing agent is the one that is reduced :)

Zainab Jamali 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!

Zainab Jamali 1H

That would be correct! I was confused by the title of your question and thought you were asking if the oxidizing agent is at the anode haha but what you have here looks accurate :)

Zainab Jamali 1H

If work is done on the system, w is a positive value. If the system does work, then w is a negative value. Hope that helps :)

Zainab Jamali 1H

The difference is in what can be transferred in/out of a system:
Open systems: mass and energy
Closed systems: energy
Isolated systems: neither

It definitely is important to know what kind of system it is, especially for thermochemistry problems!

Zainab Jamali 1H

I'm planning on taking Math 3C, LS7C, LS23L, a cluster, and a 1 unit seminar! I am a little concerned about the workload haha so I'm thinking about dropping one class depending on how overwhelming the first two weeks are :)

Zainab Jamali 1H

The way the reaction is presented to you in the problem would generally be the forward reaction (unless stated otherwise). So if that reaction is reactants --> products, then its reverse is products --> reactants. Hope this helps :)

Zainab Jamali 1H

You can use Boltzmann's entropy formula to solve for W in this question: S = (Boltzmann's constant)(lnW) --> W = e^(S/kB)

Zainab Jamali 1H

No, cell potential is not a state function but its symbol is a capital letter so I was confused too at first!

Zainab Jamali 1H

schitt's creek!!! it's such a lovable show with a lovable cast and it's pretty light which is great during exam season :) my current favorite for sure!!

Zainab Jamali 1H

A reaction at equilibrium has a delta G equal to 0 so the reaction is not thermodynamically favorable in either direction and therefore nonspontaneous.

Zainab Jamali 1H

This always trips me up when I'm trying to work quickly haha! The most definite way to know is to look at the units in your calculation and compare them to the units of the two different constants (they are very different!). Hope this helps :)

Zainab Jamali 1H

I believe he announced that midterm 2 will cover the part of outline 3 that was not on midterm 1 and all of outline 4!

Zainab Jamali 1H

My biggest tip during exam season is to get a good amount of sleep the night before! Even if it means you don't get to study as much as you think you need to, your brain will function so much better during the test. In my experience, good sleep is much more effective the night before than last-minut...

Zainab Jamali 1H

A closed system is not insulated so energy transfer can still occur but with an isolated system, energy cannot escape or enter the system.

Zainab Jamali 1H

Since it is an ideal gas, you can use PV=nRT and the given variables to solve for # of moles.

Zainab Jamali 1H

q is the measurement of heat (transfer of heat energy) and H is the measurement of enthalpy! Enthalpy is a state function but heat is not. If the system in question is at constant pressure, then I believe delta H is equal to q.

Zainab Jamali 1H

Heat capacities are always positive! Reaction enthalpies can definitely be positive or negative but the heat capacity term will always be positive.

Zainab Jamali 1H

I believe vapor refers to when a substance that is commonly liquid/solid is in the gas phase. So in calculations, you would treat gases and vapors the same way!

Zainab Jamali 1H

This happens to me a lot and what I try to do is to find a place to study that will give me a change of scenery. Either I go to the library, my backyard, my sister's room, or just somewhere where I don't feel so alone and isolated and that definitely helps me :)

Zainab Jamali 1H

I'm planning on waiting until fall 2021! I also thought it made sense to break between gen chem and o chem :)

Zainab Jamali 1H

love this positive energy :)) thanks!

Zainab Jamali 1H

K is the general variable for equilibrium constant. It can be written more specifically as Kc (concentration) or Kp (partial pressure). The one you use is dependent on the problem you're trying to solve and the given information. Hope that helps :)

Zainab Jamali 1H

Hello! I'm currently taking Chem 14BL right now, and I just want to advise that this class, while not the most difficult material, is a lot of work. So if you think you are already going to have a busy schedule next quarter, you might want to consider whether you can handle this extra workload (wee...

Zainab Jamali 1H

I totally agree!! one thing I've been doing recently to help counteract this a little bit is doing anything that doesn't involve a screen during my breaks between zoom calls. On days where I have a lot of classes back to back, I try to just take a break from screens, including my phone or TV, and go...

Zainab Jamali 1H

textbook problems and review sessions!!

Zainab Jamali 1H

When he taught %ionization in lecture, I believe Dr. Lavelle said it was the [conjugate]/[original substance] so the correct notation would be [A-]/[HA]. If the molar ratio of H+ and A- is 1:1, their equilibrium concentrations should be equal as they are both products of the reaction. Therefore, tec...

Zainab Jamali 1H

So in that situation, the heat is being used to break the bonds/intramolecular forces so it doesn't affect the actual temperature of the substance.

Zainab Jamali 1H

Hi! When the pH > pKa, the predominant species is charged because the environment around it is more basic (the pH is higher) than the species, so the acid will dissociate and become ionized to make the environment more acidic. When the pH < pKa, the predominant species is neutral because the enviro...

Zainab Jamali 1H

Generally if the relevant K value is less than 10^-4, you can approximate when finding equilibrium concentrations! You can also double check by seeing if your value for x is less than 5% of the initial reactant concentration.

Zainab Jamali 1H

You are allowed a scientific or graphing calculator, the equation/constant sheet, the periodic table, and scratch paper for the exam. Dr. Lavelle's website has the specific periodic table and equation sheet that is permitted for the test.

Zainab Jamali 1H

[H2] should be cubed rather than squared! Hope this helps :)

Zainab Jamali 1H

This might be an oversimplification but my understanding is that anything labeled in the equation with (s) or (l) should not be included in the K expression. I think only substances that are either gaseous or aqueous should be included.

Zainab Jamali 1H

Pressure and volume are inversely related. When pressure increases, volume decreases --> when there is less space to occupy (volume), the reaction will favor the side with fewer moles.

Zainab Jamali 1H

definitely disney classics!! and also harry potter (especially the early ones which are much less dark than the later ones)

Zainab Jamali 1H

inverse of Kc is to the reverse reaction what Kc is to the forward reaction. that's how I remember it!

Zainab Jamali 1H

This visual helps me remember in a really simple way! If Q>K then more reactants will form and if Q<K then more products will form in order to reach equilibrium where Q=K.

Zainab Jamali 1H

Emily Tieu 2K wrote:^ This is also my first time taking Professor Lavelle. To clarify, is it 50 times by week 10 or 5 times every week?

Technically, it is 5 posts per week but I think the grading depends on the TAs. To be on the safe side, try to do 5 posts every week :)

Zainab Jamali 1H

josephspindler2H wrote:Thanks for clarifying that the homework is due next Sunday 1/17! Out of curiosity, does anyone know if week 2 homework also be due that day?

No, the next homework assignment will include content from weeks 2-4 so it will be due the Sunday of Week 4 I believe.

Zainab Jamali 1H

The values of volume and moles can never be negative so the ratio of the two (concentration) can also never be negative.

Zainab Jamali 1H

You're correct! I believe Q can be calculated at any time during the reaction (including at equilibrium) but if it is specified that the reaction is at equilibrium you can use K instead.

Zainab Jamali 1H

When pressure is increased, the equilibrium will favor the side that has less moles of gas. When volume is increased, the equilibrium will favor the side with more moles of gas.

Zainab Jamali 1H

What does formaldehyde look like on vacation?

Casual-dehyde!

Zainab Jamali 1H

Thank you so much for this quarter Dr. Lavelle!! Your lectures were engaging and I really wish I could have taken your class in person! Nonetheless, I am really looking forward to next quarter in 14B! I hope you stay safe and enjoy the holidays :)

Zainab Jamali 1H

Hey I know how you feel, this quarter my home life was more chaotic than usual and mental and physical health issues certainly did not help my motivation. What I found to help was that for classes like this where you dread wanting to go and feel you can fall behind easily, DO IT FIRST! Its harder s...

Zainab Jamali 1H

Just finished my second final! Slowly running out of mental energy but looking forward to break :))

Zainab Jamali 1H

we have until 10 am thursday morning to post on chem community!

Zainab Jamali 1H

Zainab Jamali 3I wrote:The same thing happened to me! Once I reconnected to the campus VPN, the video loaded and started playing so maybe try that?

Actually scratch that. I am still connected to the VPN and it just stopped working again :(

Zainab Jamali 1H

I would think so because the final is cumulative for the whole quarter, but someone please correct me if I'm wrong :)

Zainab Jamali 1H

I am definitely going to take advantage of all the review sessions these week as well as Professor Lavelle's review session. I think it is super helpful to do practice problems with other students and be able to ask the UA's questions while doing so! Agreed! Also, hearing the answers to other stude...

Zainab Jamali 1H

I was wondering the same thing because midterm 1 did have partial credit opportunities but midterm 2 did not. Since the final will be cumulative, I hope at least some questions will have partial credit opportunities.

Zainab Jamali 1H

Why is it dichloro? I thought there were 3 chlorine atoms. There are only two chlorine ligands within the complex ion (within the brackets). When you name the first part of a coordination compound, you are naming only the complex ion so it would be "dichloro" and the third chlorine in the...

Zainab Jamali 1H

Ligands are listed in alphabetical order by the first letter of the ligand (not the numerical prefix). Hope this helps!

Zainab Jamali 1H

The same thing happened to me! Once I reconnected to the campus VPN, the video loaded and started playing so maybe try that?

Zainab Jamali 1H

reva_bajjuri wrote:does anyone know why exactly the ring structure is stable/what the benefit of forming a ring is?

I'm wondering the same thing!

Zainab Jamali 1H

I have been struggling with the same thing so this thread is really helpful! Thank you :)

Zainab Jamali 1H

The hydrogen bond relies partially on a partial positive charge on the hydrogen. When the H is attached to a carbon, there is very little polarity and the partial charge on hydrogen isn't there to bond to the partial negative on the bonding atom.

Zainab Jamali 1H

This is really helpful, thank you!!

Zainab Jamali 1H

I have been reviewing problems in the book and on Sapling. Are there any specific Youtube channels anyone can recommend that effectively review this course's material? Personally, I watch organic chemistry tutor on youtube when I need clarification on concepts! The videos are very detailed, clear, ...

Zainab Jamali 1H

I find that reading the textbook in conjunction with Dr. Lavelle's lectures is very helpful. If there are concepts I still can't quite grasp I definitely rely on Organic Chemistry Tutor on youtube haha. Once you have reviewed content, try testing yourself with practice textbook questions.

Zainab Jamali 1H

Thanks for asking this question! This thread is very helpful :)

Zainab Jamali 1H

The name's Bond. Ionic Bond. Taken, not shared.

Zainab Jamali 1H

A photon checks into a hotel and is asked if he needs any help with his luggage. He says, "No, I'm traveling light." :)

Zainab Jamali 1H

I think I will be taking 14B in winter and BL in spring, as I personally want to have a stronger foundation first before delving into lab stuff, but I've heard that either way you do it is fine! I'm planning on doing the same thing! I feel like knowing the textbook content well before taking the la...

Zainab Jamali 1H

Does anyone have a good way to remember which atoms can break the ocet rule during bonding, like which atoms can have an expanded octet and which atoms can have an incomplete octet (besides the first 4 elements)?

Zainab Jamali 1H

I was wondering the same thing. The question did not give the formulas for these polyatomic ions. Are we meant to know basic polyatomic ion names and charges for the midterm or will Dr. Lavelle provide the formulas on the exam?

Zainab Jamali 1H

Right! I find the overall charge helps me check to make sure I have assigned the individual formal charges correctly.

Zainab Jamali 1H

Resonance structures have delocalized electrons which are very stable and contribute to the overall stability of the molecule.

Zainab Jamali 1H

I believe formal charge is allocated per atom, but the collective formal charges of all atoms in a molecule add up to the total formal charge of the molecule. Right, that makes sense! I still would like to know if there is a way to determine which atom will hold that formal charge in resonance stru...

Zainab Jamali 1H

During last Monday's lecture, Dr. Lavelle discussed how multiple bond character was spread over the molecule in the case of resonance structures. Since adding a double bond would change the formal charge of one atom in the molecule, how is that formal charge allocated? Is it also spread over the mol...

Zainab Jamali 1H

Hi! I was wondering if someone could clarify what distinguishes a Lewis acid from a Lewis base? Is it based on whether they lose or gain electrons during bonding?

Zainab Jamali 1H

Professor Lavelle also mentioned at one point that he would not be holding office hours on Wednesday due to the national holiday so I assume that means he will not have a lecture either.

Zainab Jamali 1H

In addition, when electrons are delocalized due to resonance, it results in a more stable molecule.

Zainab Jamali 1H

There really isn't a way to determine if the electron is spinning +1/2 or -1/2. Pretty much the only practical reason why those two numbers exist is to communicate that the two electrons in the state are spinning in opposite directions, in that they are not parallel. I agree, it is simply to differ...

Zainab Jamali 1H

I would post another chemistry joke, but all the good ones Argon :)

Zainab Jamali 1H

Hi! I am currently in 14a. Personally, I have found that the lectures and sapling assignments cover the material really well. I use the textbook to review concepts and the textbook problems to prepare for the midterm exam (especially for concepts I have more difficulty with).

Zainab Jamali 1H

The simplest way to think about it is that E = hv and c = v(lambda) applies to electromagnetic radiation and deBroglie's equation applies to particles with mass, including all the subatomic particles.

Zainab Jamali 1H

For this question, you can start by finding the total number of electrons. That number is equivalent to the atomic number of the atom so, using the periodic table, you can determine what element it is.

Zainab Jamali 1H

Hi! Does anyone know where and how to access midterm exam scores when they're posted?

Zainab Jamali 1H

Hi! It is a typo in the answer key. So you're correct, \Delta v = 10 m/s. You can find the correct solution in Solution Manual Errors (https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/Solution_Manual_Errors_7Ed.pdf), which is also posted on Dr. Lavelle's website. Hope this helps :)...

Zainab Jamali 1H

Hi everyone! I am a little confused on the procedure for this question: "A bowling ball of mass 8.00 kg is rolled down a bowling alley lane at 5.00 +/- 5.0 m/s. What is the minimum uncertainty in its position?" I set up the equation using delta v = 10 because of the +/- but the answer key ...

Zainab Jamali 1H

Hi! Could someone clarify exactly which sections of the textbook will be on the midterm? I have heard a couple different answers and I just want to make sure I don't miss anything :)

Zainab Jamali 1H

Hi all! Does anyone know of any study/review sessions, official or unofficial, coming up this week? I could use the extra structured practice/study time before my exam on Friday! Thanks :)

Zainab Jamali 1H

I have found that taking notes by hand and doing practice problems are the two best ways to really lock down certain concepts! However, for some of the tougher topics I turn to youtube for some helpful tips and tricks and it can be very useful if you're having trouble conceptualizing or visualizing ...

Zainab Jamali 1H

As a follow up question, will we have access to the electromagnetic spectrum or are we expected to memorize the wavelength ranges for the different wave type?

Zainab Jamali 1H

The question is: A blue line is observed at 486.1 nm in the spectrum of atomic hydrogen. Determine the values of n for the beginning and ending energy levels of the electron during the emission of energy that leads to this spectral line. What I'm wondering is how do you determine based on wavelength...

Zainab Jamali 1H

I heard that Justin (a UA) is hosting a midterm review during his workshop on Saturday from 12-1!

Zainab Jamali 1H

How do I go about accessing the step-up sessions? And is there a pre-decided set of problems that they go over in each session and if so, would I need to complete them before attending?

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