CHEMISTRY COMMUNITY

Laura 3l

Thank you that makes sense!

Laura 3l

I feel like I would only want to move back in the dorms if we were able to have roommates!

Laura 3l

I'm not doing that well :'( I have very little motivation at this point.

Laura 3l

I plan on taking ChemBL, Stats 13 and as of now Greek Mythology for a GE. I'm on the waitlist for Anthro.2 but I really hope I get into that class :'(

Laura 3l

I try to go outside for a couple hours a day and just breathe fresh air and let the sun hit me :)

Laura 3l

I'm pretty sure you would have to know the units for pressure.

Laura 3l

There are different units for each rate of law, this way the units can cancel out.

Laura 3l

I was wondering the same thing^

Laura 3l

There were so many great performances!

Laura 3l

The pH measures the concentration of hydronium and it lets us know the pH level.

Laura 3l

My go to snack is HOT chips!!

Laura 3l

For step up sessions they are typically more thorough on the content taught in lecture and workshops are more for students who know the content they just want more practice.

Laura 3l

Yes, I would include the states of matter.

Laura 3l

Yes, you can still post but you only get a maximum of 50 points :)

Laura 3l

Im taking Chem BL next quarter and I'm a bit nervous!

Laura 3l

I'm not really sure but your assumption seems reasonable, hopefully someone else can answer this :)

Laura 3l

Thats a good question! I would assume so because a bomb calorimeter is an isolated system therefore matter and energy cannot enter or leave.

Laura 3l

A reversible work is when there is an infinitely small change in a variable, which could be external pressure, you would use the equation w = nRTln(v2/v1). Irreversible work is when a variable does not go through infinitely small changes, so you would use the equation w = -P△V. This is helpful, tha...

Laura 3l

The difference between Cv and Cp is that Cv is when volume is constant and Cp is when pressure is constant.

Laura 3l

^^Yes, Kb is on the constants and equations sheet!

Laura 3l

You are able to review them with any TA.

Laura 3l

When going from a gas to a liquid there is "more order" therefore decreasing entropy.

Laura 3l

These values are on the equation sheet :)

Laura 3l

Thank you this makes sense!

Laura 3l

I feel super nervous as well :'(

Laura 3l

Mackenzie Stockton 2H wrote:entropy (S) ---> S= KblnW1W2

its helpful to think of entropy as a measure of the disorder of a system

Thank you for putting it simply! :)

Laura 3l

I recommended Professor Dave on YouTube!

Laura 3l

Thank you for the tips!

Laura 3l

Yes, pay attention to the units and match them up!

Laura 3l

I'm also debating on taking Chem BL and C together.... I just don't want to take on more than I can handle and risk not doing well in either one.

Laura 3l

This is totally understandable, especially since we have to make sure we have enough time to finish our exams because there is a time limit.

Laura 3l

Definitely attend as many UA session as possible!

Laura 3l

In a closed system, energy can be transferred into and out of the system, however, matter can cannot.

Laura 3l

When a work is done BY the system work is negative, when work is done ON the system work is positive.

Laura 3l

Just remember that Delta H = Delta H of products - Delta H of reactants, and if your answer ends up being a positive value the reaction is endothermic and if the value is negative it is exothermic.

Laura 3l

You can find the UA sessions on Lavelle's website under "Peer Learning Sessions and Step-Up Program".

Laura 3l

Hess's Law just states that enthalpy is a state property and therefore is additive.

Laura 3l

Since sublimation is a solid changing into a gas, you need to add heat to break those bonds in order for it to become a gas, therefore making this reaction endothermic because heat is being absorbed by the solid.

Laura 3l

You would still have to include the coefficient 2 as an exponent so it would be [-2x]^2 in your equilibrium equation.
I know it seems like it is taking it into account two times but I'm honestly not sure exactly why...

Laura 3l

Endothermic will always be a positive enthalpy value and exothermic will always be a negative enthalpy value.

Laura 3l

When you reverse the reaction, K simply becomes the inverse of itself (1/K).

Laura 3l

A salt can have acidic or basic properties if it is dissolved in water. Since the salt is made up of a cation and an anion, they both can be either conjugate bases or conjugate acids that, when dissolved in water, will affect the pH. For example, with NaF, it is made up of Na+ and F-. Na+ is the co...

Laura 3l

K is calculated when the reaction is at equilibrium at a certain temperature, while Q can be calculated at anytime when the reaction is not at equilibrium at that same temperature . By solving for Q and comparing it to K you can determine which way the reaction needs to shift, if there is more react...

Laura 3l

I think it's just easier to put in Moles in the beginning when doing an ICE Box, just so you don't forget to convert the concentrations in the end.

Laura 3l

Yes can someone please help explain this, I had a hard time understanding this as well.

Laura 3l

Xinying Wang_3C wrote:Basically, the percentage ionized is the [dissociated]/[original reactant]. So you would use the ICE Table to solve for the [ H+] as usual. and just use that value to calculate [H+]/0.121 M. Hope this helps.

Yes you would do this and then multiply by 100 to get the percent ionization.

Laura 3l

I believe this only applies to gases.

Laura 3l

I will assume no because in fall quarter we didn't have the veteran's day off. If your discussion is that day though it might be cancelled. I agree^ He still posted a lecture under the media tab for Veteran's Day since we do not have live lectures I don't think he'll give us the day off from a lect...

Laura 3l

We get points for both!

Laura 3l

I was honestly confused by that too because he then goes on by saying that the equilibrium constant for this reaction is Ka because we have a weak acid in our reaction.

Laura 3l

How I think of its is "Bases want H's" so when a base reacts with water, that reaction's product will include an OH- because "the base wanted the H and took it from the water" and therefore forms hydroxide(OH-). When thinking of acids I just think acids donate protons so when an ...

Laura 3l

This value is a constant and is given to us because like everyone else has said, it is a value that was experimentally determined.

Laura 3l

I believe you are correct I was wondering the same thing because I ran into another post that confused me because of the wording that was used, but I do believe yo0u are correct!

Laura 3l

Yes homework is on Sapling and there are unlimited tries for each problem!!

Laura 3l

This is also a sapling related question but I'm having trouble figuring out where to go for the Chem14B homework... I took 14A last quarter so all I see is my work from Chem14A. Does anyone know how to access the Chem14B homework?

Laura 3l

Do the Q and the K values follow the same trend/pattern when describing on whether a system will favor reactants/products? For example in the lecture, it states if K is small, then it would favor the products (shift right) since there's more reactants at equilibrium. And if Q is smaller than K, the...

Laura 3l

If K is less than 1 then that means at equilibrium the reactant is larger than the product. Therefore, the reactant is being favored.

Laura 3l

I'm so happy the final for this class is over since its my hardest class!! I can't wait for Winter break so I can relax and not stress about school for 2 weeks!! :)

Laura 3l

We have until Thursday morning to complete our Week 10 posts on Chemistry Community.

Laura 3l

Thank you for setting up the many hours of review and study sessions that are SUPER helpful throughout the quarter, please keep doing this! :)

Laura 3l

That sounds like it will be a blast!! I will be visiting my mom for Christmas in Texas and just relaxing as much as I can before I go back to stressing about school!

Laura 3l

I’m very reward oriented, so to motivate yourself to watch the lectures or do homework I recommend giving yourself little gifts when you complete the tasks! For example if you watch a couple of lectures and do the work problems, then you get to order a pizza or do a facemask or something you enjoy....

Laura 3l

I had the same problem, I just waited it out :/

Laura 3l

Professor Dave really helped me! :)

Laura 3l

Ryan_Page_1J wrote:Fun Fact: The organic chemistry tutor on YouTube got his bachelors degree here at UCLA :)
All the more reason to watch him

Wow really?! Great fun fact lol!

Laura 3l

Shail Avasthi 2C wrote:If an acid has more than one hydrogen which it can dissociate, it is polyprotic.

This makes sense, thank you!

Laura 3l

Haochen He 3L wrote:Hi! I am not sure how to determine and compare the acidic strength between H3PO3 and H3PO4.
Could someone explain it?

H3PO4 is more acidic since this compound has an extra O and resonance, therefore it is more stable meaning it is more acidic.

Laura 3l

Hello! For the conjugate acid of HSO4- I put H3O+. Is that not the conjugate acid? When thinking about what it is asking for, the conjugate acid, first think about what that means. A base turns into a conjugate acid because when doing the reverse of the chemical reaction it would go back to being a...

Laura 3l

It's okay, its totally understandable!

pH=-log([H+])...so to find [H+] when given pH you do the reverse which would be...[H+]=10^-pH

Laura 3l

Lea Ozdere 1A wrote:Does anyone have good studying tips for the final? Other than the sapling and textbook problems. Any methods or sites that are really helpful?

UA Sessions are SUPER helpful, HIGHLY recommended!!! I would also recommend the review session Professor Lavelle recently organized.

Laura 3l

After taking the second midterm, I just realized how many mistakes I made and how probable it is that I am not going to pass it haha. While there are students worried about getting an A-, I am worried about getting a passing grade haha. For those of us who have taken it, how are you feeling? I feel...

Laura 3l

The oxidation state is the number of electrons lost or gained in a chemical compound.

Laura 3l

I'm having the same problem! If anyone would mind explaining that would be super helpful! I thought it was 4, but it says it is incorrect.

Laura 3l

From what you gave it seems like there are three chlorides so maybe the oxidation state of Cobalt is (III) and not (II). So it would be tetraaminechlorocobalt(III) chloride. For example, [Co(NH3)6] Cl3 which is HexaammineCobalt(III) Chloride. I also had an issue with this problem, make sure you use...

Laura 3l

He stated in an email that he is not sure if he will be able to continue asynchronous lectures for Winter quarter like he has for this Fall quarter. He may not get approved to be on campus and/or have BruinCast to record his lectures. He also mentioned that students who plan on taking Chem14B this W...

Laura 3l

Since there are four regions of electron density, three bonds and one lone pair, this means that the hybridization of this molecule is sp^3 (s, p, p, p).

Laura 3l

I was also confused on the grading scale because I also saw that in the syllabus. Does anyone know what the in between grades are if a C- is 50%? Like what is the percentage gap between a B+ to a B- ?

Laura 3l

H20 would have a bent shape since there are 4 electron domains; 2 being lone pairs and the other two being bonds.

Laura 3l

Since the final is cumulative, will the majority of the questions on the final be on the latest topics we've covered rather than content from midterm 1 and 2?

Laura 3l

A molecule can be polar because of the dipoles occurring between each atom, but when all the atoms have the same "pull", electronegativity difference, they can cancel out resulting in the whole molecule to be nonpolar.

Laura 3l

I was having a hard time with the Lewis acids and bases too, can someone please explain the difference. it helps to have a visual structure of the molecules/atoms so you can see whether there are any lone pair electrons that can be shared (Lewis base) or if it's deficient in electrons (Lewis Acid)....

Laura 3l

How I think of polarity is that the atom with the more electronegativity is "hogging the electron" which results in a partial negative and partial positive.

Laura 3l

victoria_dao_3L wrote:This class gives a lot of stress considering that we basically only have three exams that determine the majority of our grade, but seriously no worries! We've all got this!

I know right! Midterms for this class are finally over and I'm already worried about the final for this class *crying emoji*

Laura 3l

I feel way better about this midterm but am really anxious for the final!!! Does anyone know when scores will be released?!

Laura 3l

I believe this is because the stronger Intermolecular forces there are between molecules, the higher the boiling/melting point will be.

Laura 3l

I was having a hard time with the Lewis acids and bases too, can someone please explain the difference.

Laura 3l

Hi! I don't believe we would have to just because we didn't really go into resonance hybrid structures that much. As for drawing them for the midterm, I feel like we wouldn't have to since it is multiple choice, I could be wrong though.

Laura 3l

I believe since this is a dipole dipole force then it would also be a Hydrogen bond.

Laura 3l

Electronegativity and electron affinity have the same trend on the periodic table (increasing up and to the right), but they are different because electronegativity is the ability of an atom to hold onto their electrons tightly and electron affinity is how many electrons atoms want to gain.

Laura 3l

I had the same question! I'm still kind of confused, but does anyone know how to calculate the oxidation number?

Laura 3l

Andy Hernandez wrote:Why is 4s filled first?

4s is filled first only if the 3d orbitals are not being occupied.

Laura 3l

905579227 wrote:Wait so we wont know until end of week five!? lowkey nervous. Does anyone know how it is actually graded because i have heard alot of mixed results.

I hope the midterm grade comes out soon, I'm also nervous!

Laura 3l

I enjoy going on drives while vibing to music and also just watching my show on Hulu :)

Laura 3l

Mahnoor_Wani_2F wrote:I did chemistry and LS30A homework for halloween

Me too lol!

Laura 3l

Samin Kabir wrote:When do we get the midterms back?

I was also wondering the same thing...

Laura 3l

Funmi Baruwa wrote:What exactly does the spin state of an electron tell us about an electron?

I have the same question. ^

Laura 3l

When will our final grades from the midterm be posted? Also, I heard someone say Lavelle may be offering partial credit? How would that be the case because they are multiple choice? My TA said probably after this Friday our midterm grades will be up. As for the partial credit, I feel like since som...

Laura 3l

Jacquelyn Challis 1H wrote:Does anyone know how many questions will be on the midterm and/or how much time we'll have to complete?

There are 12 questions and you will have 56 minutes.

Laura 3l

You are able to go back and review questions. Goodluck on all your midterms!

Laura 3l

I also keep clicking on my name to view my points but it is not showing. Where do we click again to view our points?

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