CHEMISTRY COMMUNITY

Margaret Wang 2D

The person above me explained it beautifully. I personally struggle with this a lot as well but I found these videos super helpful, give them a watch!
https://www.youtube.com/watch?v=v5sDNmYCaqo&t=929s
https://www.youtube.com/watch?v=N6ivvu6xlog&t=306s

Margaret Wang 2D

Yes, the transition states are always at the peaks of free energy diagrams.

Margaret Wang 2D

I believe they are both approaches to determine the rate-limiting step reaction mechanism, and he said he will touch upon it next lecture so we don't have to know about it right now.

Margaret Wang 2D

I find that writing everything down by hand on an iPad is the best way for me because it saves paper and it also forces me to concetrate during lectures. Although I don't really use the notes when I'm studying or doing problems because I use the equation sheet, it's still helpful because I think it ...

Margaret Wang 2D

The final was more challenging for me last quarter but that was mostly due to the fact that there's way more material covered and I just could not extensively study everything. I did do noticeably worse on my final than my two midterms last quarter, so I'm definitely nervous right now.

Margaret Wang 2D

I've never been to campus (freshman) but I'm actually visiting during spring break so I'm really excited to just even know what the west coast is like since i'm from the east coast.

Margaret Wang 2D

To add on to what everyone already said, it's the same thing with Gibbs free energy we did. G naught is under standard conditions and G is under any conditions. hopefully relating the two will help us remember!

Margaret Wang 2D

I've been obsessed with Redbone by Childish Gambino recently even though it's an older classic haha

Margaret Wang 2D

I can't say I have favorites because I don't really watch shows too often, but recently I've started Handmaid's Tale and Emily in Paris which I enjoy

Margaret Wang 2D

In 14A last quarter, Professor Lavelle said that the questions will be allocated according to how much time we spent on each one (aka how long the outlines were relative to each other), so I would assume it's mostly equal. However, I will note that I recall last quarter in 14A we spent less time on ...

Margaret Wang 2D

I didn't do as well as I hoped either, and I fault that on myself for not redoing all the textbook problems, so I will be doing that.

Margaret Wang 2D

Personally, I like to stick with what i learned in high school which is OIL RIG: Oxidation is Loss (OIL) Reduction is Gain(RIG)

Margaret Wang 2D

Sushi gang rise up! Honestly, any kind of Asian food tbh.

Margaret Wang 2D

I only started organizing everything in a google calendar tab i have open 24/7 starting in college, and i have noticed that it's made things a lot less stressful in terms of managing my schedule.

Margaret Wang 2D

From what I remember from high school, oxidation of oxygen is usually always -2 and hydrogen +1. Only elements in compounds have oxidation numbers. The other elements can be determined by adding up the oxidation numbers in the compound and setting that equal to the overall compound charge. For examp...

Margaret Wang 2D

Entropy is disorder. For example, gas has significantly higher entropy than liquid because gas molecules have way more space to move around and be disorderly.

Margaret Wang 2D

Yes, it will be. Only difference is it might not necessarily be the same time (Friday at 1pm) because we don't have designated lecture slots in finals week.

Margaret Wang 2D

Delta G naught is never 0. It is a constant value for a given reaction. Delta G naught. = -RTlnK because K is also a constant for a given reaction. Delta G (without the naught) changes depending on where you are in the reaction, as in you can calculate Delta G at any time in the reaction but you can...

Margaret Wang 2D

Equilibrium is very useful for biochemical and molecular biology research because researchers often deal with the concentrations of biomolecules in cells and how an enzyme catalyzes these reactions to equilibrium. I remember when I did biochemical research, we would put molecules and enzymes in the ...

Margaret Wang 2D

The second law of thermodynamics states that the entropy of the overall universe is always increasing (positive), but it is always possible for a certain smaller section of the universe to decrease in entropy.

Margaret Wang 2D

Usually, what works for me is I attend as many UA sessions as I can fit into my schedule and make sure to start doing problems early enough so I can finish all problems by midterm day.

Margaret Wang 2D

In reversible expansion, all of the energy put to expand is actually 100% used up to do work of expansion, which needs to be slow and gradual, otherwise it won't be 100% efficient. In irreversible expansion, only some of the energy is used to do work of expansion, the rest is released as heat, which...

Margaret Wang 2D

Last quarter he did not curve anything so i don't think he will this time either. The only boost we got was an extra 10 points last quarter on the final, which isn't really a curve.

Margaret Wang 2D

It all depends on how far we get in lecture by this friday, which can vary depending on what goes on in the lecture so that's why Professor hasn't told us yet, since it's not like all our lectures are prerecorded

Margaret Wang 2D

I think about it like this: If you're doing work to move something, you're exerting energy, so you're spending positive energy. So, similarly, if the gas is working to expand and thus move the piston, the work is positive.

Margaret Wang 2D

Oh boy, I didn't realize they weren't on the sheet! I starrt better memorize them now!

Margaret Wang 2D

I think that if you do practice problems, you can identify a pattern in the way different categories of questions are phrased, and then you can match those categories to the equation they use in the answer key. Honestly, that's the best I can come up with and what I would do, but other people may ha...

Margaret Wang 2D

Residual entropy quantifies the uncertainty in molecular orientation. It is the difference between a perfectly still, crystalized state of a substance versus a more unstable form (liquid, gas).

Margaret Wang 2D

I'm currently taking 14B, planning to take BL next quarter and take a break from regular chemistry classes and take chem14c starting fall next year (fingers crossed it'll be in person)

Margaret Wang 2D

I was a little nervous because a few questions tripped me up with the wording where I wasn't sure how to interpret the question, but luckily I interpreted the right way, so I guess my result was better than I anticipated.

Margaret Wang 2D

In my experience, passively reading the textbook or watching the video doesn't help much because it's too passive and you can get easily distracted. When you do practice problems, it forces you to focus.

Margaret Wang 2D

If you're asking about studying specifically, I really like instrumental or chill R&B stuff because it doesn't distract me.

Margaret Wang 2D

To add on to the posts above, I believe it can also be questions where they are two blanks to fill and if one of them is correct you get 5 points out of 10 for that question.

Margaret Wang 2D

Gases change volume and/or pressure when they are heated/cooled. Solids and liquids don't do that.

Margaret Wang 2D

Since 5 mL of the original solution was taken and diluted into 500 mL, then the original solution would be 100 times more concentrated than the diluted solution which you know the pH of and you have already calculated the concentration of.

Margaret Wang 2D

I'm logging in just fine. Is it because you don't know the password?

Margaret Wang 2D

When combining different reactions, multiplication is used for adding reactions and division is used for subtracting reactions. Adding and subtracting the equilibrium constant values never happens.

Margaret Wang 2D

I'm like 99% sure we don't have to know these by memory. There's a table in the textbook section above the questions, I believe, with all the values.

Margaret Wang 2D

Like previous posts state, if H2O is in gas form (water vapor) then it would be included. Dr. Lavelle also stated in his lecture that an example would be if the solvent was a different liquid substance, not water, and instead, water was acting as a reactant that gets consumed in producing the produc...

Margaret Wang 2D

I feel you! I think what motivated me to keep up with online stuff is I use Google Calendar and I write down every lecture, meeting, assignment, etc. I keep the calendar tab open and I never close it, so I'm constantly reminded to check for due dates.

Margaret Wang 2D

The equilibrium favors/leans/etc towards a side is talking about the ratio of products to reactants (K). For example, if K is really large, that means the ratio at equilibrium has way more products (on the top of the fraction) than reactants (below the fraction), but the reaction reached equilibrium...

Margaret Wang 2D

The question states that the water is neutral, and anything with a neutral pH has equal amounts H3O+ as it does OH-, otherwise if one was more than the other it wouldn't be neutral.

Margaret Wang 2D

There should be a separate section if you go to the index page and scroll down further to a section labeled for 14B

Margaret Wang 2D

I want to focus on self care more. I used to be really hard on myself and it really stressed me out, I had anxiety constantly. This year I want to relax a tiny bit more so my mental health is better. So far it's going pretty well, my stress and anxiety levels have visibly decreased.

Margaret Wang 2D

To add on to the reply above, essentially K is not dependent on the current state of the reaction and Q is dependent on the current state of the equation. K is basically an intrinsic property that the reaction under a certain temperature will always have, whereas Q is just a number that characterize...

Margaret Wang 2D

If it's in the liquid state it is considered a solvent/pure liquid, so no. However, if it is a gas (g) then it needs to be included.

Margaret Wang 2D

Changing volume does not impact the equilibrium constant, provided all other conditions are the same. Temperature on the other hand does change the equilibrium constant.

Margaret Wang 2D

I actually have the same question! I think maybe check if your TA from 14A is still a TA, because if they're not anymore it may be hard for them to reach out to the Professor and get the test

Margaret Wang 2D

K is a broad term for the equilibrium constant. Kc and Kp are more specific versions of the equilibrium constant, although most of the time K means Kc (from my observations)

Margaret Wang 2D

I'm pretty sure Professor Lavelle stated that the 10^3/10^-3 boundaries are for whether or not the reaction strongly favors reactants/products, not if they do at all.

Margaret Wang 2D

Dr. Lavelle mentioned in today's lecture that F- has the ability to act as a weak base by pulling off a proton from water and forming OH-. On the other hand, both K+ and Br- are too weak to disrupt any bonds in H2O to act as an acid or base

Margaret Wang 2D

Weaker acids do not give off all the protons they have available, whereas strong acids give off essentially all of their available H+ to form H3O+. For example, HCl would give off every single H+ from every single HCl molecule when put in water, whereas acetic acid CH3COOH may only give off 50% (I m...

Margaret Wang 2D

Hi! Does anyone have any good resources for all the common ligand names we need to memorize for the exam? As well as which common ones are polydentate ligands. Thanks!

Margaret Wang 2D

To make a conjugate acid, you add an H+
To make a conjugate base, you take away a H+

For example, the conjugate acid of NH3 is NH4+
the conjugate base of NH4+ is NH3

Margaret Wang 2D

Yeah they're definitely very closely related! Especially since in a lot of our lectures Dr. Lavelle often mentions that we will cover more in-depth on a topic in 14B and he also said a few times how we're setting up to understand 14B

Margaret Wang 2D

The only prefix that would change is the one that goes before the whole ligand name. For example, 2 of ethylenediamine would be bis(ethylenediamine) since the original name already has "di-" amine

Margaret Wang 2D

I don't think there are any exceptions to this because pi bonds are parallel and any sort of rotation would break them.

Margaret Wang 2D

I believe on his website he has a sheet with all the common ligand names and oxidation numbers. I'm not sure if we will be given this sheet during the final, but it might be helpful to know the anyway in the long run.

Margaret Wang 2D

It doesn't because single, double, and triple bonds in one location are all considered one region of electron density so it will result in the same shape!

Margaret Wang 2D

The transition metals we will be working with will mostly be the 1st row ones, which he said would be 6 bonds max normally.

Margaret Wang 2D

Agreed, I think the only way is to memorize them. Thankfully, there's not that many different ones we have to memorize since a lot of molecules have the same shape and therefore the same angles.

Margaret Wang 2D

I do a loooooot of practice problems to the point where I know that there's literally nothing more I could have done to prepare so there's no point in being nervous because I have already tried my best.

Margaret Wang 2D

Something that really helped me was that I used to study in the desk in my room but I would often get distracted there because that was also the place where I would relax and play video games and watch youtube videos. So when college started I set up a little new study area downstairs (just a table ...

Margaret Wang 2D

You can't know the specific length of bonds in a resonance structure, just that it is between two numbers. As stated above, assign formal charges to every atom of every resonance structure and the ones with the most formal charges closer to 0 contributes the most.

Margaret Wang 2D

My studying strategy was just doing practice problems! Aside from the textbook ones, I did the problems from worksheets given by the UA sessions. They're similar to textbook problems so they're basically just additional practice. Also, if there was any particular topic I did not understand, I search...

Margaret Wang 2D

I wasn't as confident with this one as I was with the first midterm. Fingers crossed! Good luck everyone

Margaret Wang 2D

Nope. Nitrogen is Period 2. Only elements in the p block that is period 3 and down can have an expanded octet. This is because the d subshell starts at 3d, there's no 2d subshell. The d subshell is what allows for an expanded octet.

Margaret Wang 2D

If you have two double bonds and a single bond on a nitrogen, the nitrogen would then have 10 electrons. Nitrogen cannot have more than 8 electrons in its valence shell. Only Period 3 elements and down can do that.

Margaret Wang 2D

Dr. Lavelle said the arrow goes from positive to negative, so the first one!

Margaret Wang 2D

He stated in another post (which he sent out in an email) that he will try his best to make them asynchronous but it's not guaranteed since the school has to approve it first (with Bruincast and testing to come on campus and everything.

Margaret Wang 2D

Clarifying question, is the major difference between dipole and induced dipole the permanence? Like, is a dipole a property of a molecule while induced dipoles only happen when in the proximity of other molecules or ions that can cause distortions? Yes exactly! A dipole or dipole moment is always p...

Margaret Wang 2D

A dipole moment is present at a polar covalent bond, when there is unequal sharing of electrons between a covalent bond. Also can be thought of as a covalent bond with ionic characteristics but also not a full ionic bond

Margaret Wang 2D

Usually for these type of trends, noble gases (which Helium is one) are excluded because they are exceptionally stable and unreactive.

Margaret Wang 2D

A hydrogen bond is a type of dipole-dipole bond, but it is special in that it is usually slightly stronger than typical dipole-dipole bonds.

Margaret Wang 2D

They are negative because it is more favorable for these interactions to happen. It is a similar concept to bonds, where it is more favorable for two atoms to bond together than not. So, when you break that bond you need to input energy (positive), so when the bond is formed energy is released and i...

Margaret Wang 2D

L is the number of electrons in lone pairs (aka not bonded with another atom). It should be represented by dots so you just need to count the dots around the Lewis structure

Margaret Wang 2D

I had the same question! In highschool, I learned to write 3d after 4s. However, Lavelle said in his lecture that when 3d is filled it is lower in energy and should come before 4s. I then saw my TA write 3d after 4s, so I asked her, and she said both are fine, so I'm kind of confused as well.

Margaret Wang 2D

Ionization energy and electronegativity are synonymous, so they have the same periodic trends, so I believe you can use either

Margaret Wang 2D

Either equation should work, but the E=hv equation can work for any instance whereas the one with the work function is only in the case where the photons are hitting a metal and ejecting electrons from it, so it's a more specific case.

Margaret Wang 2D

I personally have not attended any of the live sessions but I save all the problems/worksheets that are done in the sessions and I did them all the days before the midterm and they really really helped. So, I don't believe it's necessary to attend them live, but having the extra practice is helpful.

Margaret Wang 2D

605.8 nm should be visible light because the visible region is 400 to 700 nm. I was told by my TA and peers that we have to know the regions roughly, so I would take a look at the spectrum by just googling "electromagnetic spectrum"

Margaret Wang 2D

Z is the atomic number (how many protons it has in the center). For example, for carbon, it would be 6. If an atom has Z electrons, it means it's a neutral atom because it has the same number of electrons as protons, since an atom's atomic number is how many protons it has.

Margaret Wang 2D

"Shell" refers to the first quantum number, n "Subshell" refers to the second quantum number, l "Orbital refers to the third quantum number, ml For example, for "2px" the shell is n=2, the subshell is 2p, and the orbital is 2px Here's a photo i found that can proba...

Margaret Wang 2D

Yep! It is 3d1 then 4s2
I'm honestly a little surprised/confused by this since i've learned in both high school chemistry and ap chemistry to write 3d after 4s in all electron configurations... oh well

Margaret Wang 2D

I believe we don't have to because it doesn't Outline2 does not even list the rule names besides Aufbau's, but I could be wrong.

Margaret Wang 2D

When atoms come together and share electrons, the electrons are behaving differently (different orbitals, wavelengths, energies) so they're not the same as if they were independent. As the people before said, it's the ratio of the molecules.

Margaret Wang 2D

Photons have no mass because they are electromagnetic radiation. Electromagnetic radiation particles do indeed have momentum, but the equation p=mv does not apply for photons. It is one of those logic things where everything with mass has momentum (p=mv) but not everything with momentum has mass.

Margaret Wang 2D

The De Brogile Equation can be used for anything that has a mass and is moving (velocity). Photons do not have mass because they are electromagnetic radiation so the equation cannot be applied to photons

Margaret Wang 2D

The mass of an electron is 9.11x10^-31, where as you can see the exponent for the 10 is really small. For the velocity of electrons, it is usually around 10^4 or 10^5 (it can't go above the speed of light which is 3x10^8). So, when you multiply the mass by the velocity, the extremely negative expone...

Margaret Wang 2D

That's the mass of an electron and it's given on most if not all constant sheets usually, so don't worry about memorizing it.

Margaret Wang 2D

Intensity refers to the number of protons emitted from the light source. For example, if you have 1 photon emitted from the source and hitting the surface per second, that is less intense than if 5 photons were hitting the surface per second (the numbers are usually way higher than this obviously). ...

Margaret Wang 2D

I took quantized to mean "specific" small amounts

Margaret Wang 2D

I actually have the exact same question!

I was thinking that maybe the electron will just barely leave the atom's grasp, but it won't really travel away from the atom, but I'm not really sure. That's just a speculation. Hope someone can give us a better explanation

Margaret Wang 2D

The work function is also known as the threshold energy, the energy needed to eject an electron. From what I understand, we will always be given the value. If we need to solve for it, it'll be with the equation E(photon) - (work function) = E(excess) and never any other way.

Margaret Wang 2D

Is this a textbook problem?

Margaret Wang 2D

Yes. The 10*-3 caused by the milli appears on the both the top and bottom and so cancel each other out to give you mol/L

Margaret Wang 2D

I started by counting the number of each atom in the molecules and turned it into a normal chemical equation with letters, and then the problem looks much more doable from there. The key thing to know is that each corner is a carbon, all the other atoms are written out.

Margaret Wang 2D

Like the other posts said, unless the problem specifies a unit to use for the answer, SI units would probably be best. For working through the problem, I *personally* always convert to SI units no matter what just because that way everything is standardized and I have no chance of messing up. But yo...

Margaret Wang 2D

Combustion always means that a reactant is reacting with O2, and CO2 and H2O will always be products (the coefficients will vary)

Margaret Wang 2D

I feel like it's always good to check. The few seconds it takes to check beats wasting time realizing later. I've had many instances where I didn't check to see if the equation was balanced and just went ahead with the problem, and then realized when I've completed all the necessary steps that I had...

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