CHEMISTRY COMMUNITY

Jacquelyn Challis 2B

uclakat wrote:Breathe in the weed, breathe out the BS.

HAHAH this is awesome. Thank you for the tip:)

Jacquelyn Challis 2B

Anything besides thermodynamics :)

Jacquelyn Challis 2B

I'm feeling really burnt out. The only thing keeping me going right now is spring break and the hope that life may get back to normal soon.

Jacquelyn Challis 2B

I like handwriting my notes as well. I find i remember it better when I write it down.

Jacquelyn Challis 2B

abby hyman wrote:They are due Sunday as per Dr. Lavelle's email

Thank you!!

Jacquelyn Challis 2B

Do you know who the professors are that do teach 14C.

Jacquelyn Challis 2B

They are represented by two vertical lines that looks like this: II.

Jacquelyn Challis 2B

An intermediate is a species in the reaction that is created as a product and then consumed in another step. It does not appear in the overall reaction

Jacquelyn Challis 2B

I'm just praying for a passing grade at this point:) I'm really hoping in person classes resume soon because I don't think I'm learning as well online.

Jacquelyn Challis 2B

Thank you Dr. Lavelle!!

Jacquelyn Challis 2B

I will be taking 14BL over summer:)

Jacquelyn Challis 2B

What are standard conditions?

Jacquelyn Challis 2B

Thanks everyone!!

Jacquelyn Challis 2B

Okay, thank you!

Jacquelyn Challis 2B

Do we need to know/understand the Daniell cell diagram? The syllabus only mentions Galvanic and voltaic cells but the textbook mentions it.

Jacquelyn Challis 2B

Can anyone clarify in really simple terms what oxidation vs. reduction means? And how that takes places in a Galvanic cell?? Thank you!!

Jacquelyn Challis 2B

Thanks!!

Jacquelyn Challis 2B

This question says: Consider a process in which an ideal gas is compressed to one-eighth of its original volume at constant temperature. Calculate the entropy change per mole of gas.
I know the equation is delta S=nRln(v2/v1) but how do i find n, the number of moles?

Jacquelyn Challis 2B

For an old Sapling question ( weeks 3/4 #20), the feedback says: First, determine the appropriate expression for the molar heat capacity at constant volume (Cv,m). This is based on the molecular shape of the gas, whether it is an atom, a linear molecule, or a nonlinear molecule. How do I determine t...

Jacquelyn Challis 2B

I am in the exact same boat so I'll be cramming all day today and Saturday as well! Wishing you luck:)

Jacquelyn Challis 2B

This is all really helpful! thank you all!! :)

Jacquelyn Challis 2B

The question gives the equation: H^(+)(aq) + Cr2O7^(2−)(aq) + C2H5OH(aq) → Cr^(3+)(aq) + C2H4O(aq) + H2O(l) The answer says that Cr is reduced from 6+ to 3+ and that C is oxidized from 2- to 1- How would I know this? In other words, what steps do I take to figure out which elements are oxidized and ...

Jacquelyn Challis 2B

Hi, thank you for your feedback!! Cp=5R/2

Jacquelyn Challis 2B

I'm working on sapling question where I am given the constant‑pressure molar specific heat, (Cp) and I need to find the constant‑volume molar specific heat of the gas.
The hint asks me: How does Cv relate to the constant‑pressure molar specific heat, Cp? Can anyone help me with this?

Jacquelyn Challis 2B

Thanks everyone!

Jacquelyn Challis 2B

An old sapling question that I never answered says: Automobile airbags contain solid sodium azide, NaN3, that reacts to produce nitrogen gas when heated, thus inflating the bag. 2NaN3(s)⟶2Na(s)+3N2(g) Calculate the value of work for the system if 32.0 g NaN3 reacts completely at 1.00 atm and 22 ∘ C....

Jacquelyn Challis 2B

I'll be spending my time sleeping and trying to avoid school as much as possible:)

Jacquelyn Challis 2B

Thank you!

Jacquelyn Challis 2B

Thanks! Regarding what you said about the spontaneity, which signs of enthalpy and entropy make a reaction spontaneous or not spontaneous?

Jacquelyn Challis 2B

I'm a little confused about the T in the Gibbs equation. Because it's not a delta T, does it mean the change in temperature, the final temperature, or the starting temperature? Or will I just be given one temperature value to use in a problem using this equation?

Jacquelyn Challis 2B

Okay, great. Thanks!

Jacquelyn Challis 2B

The question asks which system does more work: an irreversible reaction or a reversible reaction. The textbook's answer goes through the steps of calculating the amount of work done by the irreversible expansion. But, the textbook also said that "the greatest work done is for a process that tak...

Jacquelyn Challis 2B

Why do we convert to Liters in part a when finding volume? Is that so we can later make the conversion of 1atm x 1L = 101.325 J?

Jacquelyn Challis 2B

I think all the equations we would need will be on the constants and equation sheet.

Jacquelyn Challis 2B

Can someone walk me through the steps to solve a question like this? I have a general idea but I must be doing something wrong because I can't get the right answer.

Jacquelyn Challis 2B

Thank you for this!

Jacquelyn Challis 2B

Is there a relationship between the strength of the bonds in a reaction and whether or not that reaction is endothermic or exothermic? If so what is it?

Jacquelyn Challis 2B

I would also agree with lots of practice! I know Lavelle mentioned this quarter was going to consist of more problem solving than last quarter so I think it would be especially helpful to get more practice in as a study tool.

Jacquelyn Challis 2B

Thank you!

Jacquelyn Challis 2B

Okay, I see where I was stuck. Thank you!

Jacquelyn Challis 2B

Thank you all!!

Jacquelyn Challis 2B

^^^ same, waiting for the day that SZA drops her new album.

Jacquelyn Challis 2B

The value of Kw for water at body temperature (37 °C) is 2.1×10−14. (a) What is the molar concentration of H3O+ ions at 37 °C? (b) What is the molar concentration of OH− in neutral water at 37 °C?

Are you supposed to assume [H30+] and [OH-] are equal and divide Kw by two?

Jacquelyn Challis 2B

I don't think so, I'm pretty sure he only teaches 14A and 14B.

Jacquelyn Challis 2B

A reaction mixture that consisted of 0.400 mol H2 and 1.60 mol I2 was introduced into a flask of volume 3.00 L and heated. At equilibrium, 60.0% of the hydrogen gas had reacted. What is the equilibrium constant K for the reaction H2(g) + I2(g) ⇌ 2HI(g) at this temperature? I'm confused on how to go ...

Jacquelyn Challis 2B

I'm trying to answer this question, but I'm stuck. I know you line them up but do I add all the values or subtract to find a difference or something else? The example in the book seems to confuse me more so if anyone can let me know the steps to get through a problem like this that would be great:)

Jacquelyn Challis 2B

I'm working through this module and I'm not sure if I'm doing this right. #14 says: The two air pollutants SO2 and NO2 can react in the atmosphere as follows: SO2 (g) + NO2 (g) ⇌ SO3 (g) + NO (g) Predict the effect of the following changes to the amount of NO when the reaction above has come to equi...

Jacquelyn Challis 2B

Thank you all!!

Jacquelyn Challis 2B

17. You are studying the following unbalanced reaction at high temperatures: NH3 (g) ⇌ N2 (g) + H2 (g) In one of your experiments at 500K the measured partial pressures are: NH3 0.887 bar H2 0.168 bar N2 0.0561 bar a) Determine the equilibrium constant for this reaction at 500 K. I don't really unde...

Jacquelyn Challis 2B

Why are equilibrium constants useful? I answered: One number that gives us information about the relative production rates of reactant and product. But that was wrong, so I'm wondering what the correct answer is. Thanks!!

Jacquelyn Challis 2B

Also I would say make sure you're getting every point you can. Do all of the chemistry community points and homework points, because these are huge grade boosters and can really determine a passing grade from a failing grade in the end :)

Jacquelyn Challis 2B

Just hyped to be done with finals:))

Jacquelyn Challis 2B

Thank you to everyone!!! Especially with the adjustment of teaching online classes!

Jacquelyn Challis 2B

To stay on top of my recorded classes for winter quarter :)

Jacquelyn Challis 2B

Manifesting good grades to everyone!!

Jacquelyn Challis 2B

Thank you Dr. Lavelle!!! You made me enjoy chemistry again:)

Jacquelyn Challis 2B

Question 9C.5 says: Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center: (a) HN(CH2 CH2 NH2)2 ; (b) CO3 2 − ; (c) H2O; (d) oxalate. I'm not really sure what a polyde...

Jacquelyn Challis 2B

Thank you for this! How would I find the charge of the ligand as well?

Jacquelyn Challis 2B

Does anyone know where in the book it goes over these steps for naming?

Jacquelyn Challis 2B

Does s & p character just mean how many s & p orbitals there are? like p character would be increasing from sp to sp2?

Jacquelyn Challis 2B

Do lone pairs come into play in hybridization? If a molecule has a lone pair, I know it affects the shape so how does that correlate to the hybridization?

Jacquelyn Challis 2B

Okay, so 2.F.1 says: State the relative orientations of each of the following hybrid orbitals: (a) sp3 ; (b) sp; (c) sp3d2. So if there are multiple shapes that have sp3 or sp2, could there be two answers for part a of this question?

Jacquelyn Challis 2B

Thanks for this!!!!!

Jacquelyn Challis 2B

Thank you!! I've been trying to find a good chart :)

Jacquelyn Challis 2B

How do you determine whether the salt is acid or basic?

Jacquelyn Challis 2B

the textbook's answer says, "the smaller the pKb of a base, the stronger the base. pKb (morphine)= 5.79. pKb (BrO-)= pKw-pKa=14-8.69=5.31." This reasoning is confusing me because I don't know how they calculated pKb and pKa. Can anyone explain how they got those numbers?

Jacquelyn Challis 2B

the textbook's answer says, "the smaller the pKb of a base, the stronger the base. pKb (morphine)= 5.79. pKb (BrO-)= pKw-pKa=14-8.69=5.31." This reasoning is confusing me because I don't know how they calculated pKb and pKa. Can anyone explain how they got those numbers?

Jacquelyn Challis 2B

In today's review session with Lavelle, he went over several problems from the midterm and showed the answers, so if you weren't able to get your answers from your TA, you can watch the recording of this review session, which Lavelle sent a link to in an email today.

Jacquelyn Challis 2B

I'm pretty sure Friday's is recorded, not live.

Jacquelyn Challis 2B

Same, looking through my notes after I realized that a bunch of my answers were wrong:( I feel like I made a lot of small mistakes on this one.

Jacquelyn Challis 2B

Got it, thanks!!

Jacquelyn Challis 2B

Just to clarify, when writing electron configurations, would you write 3d or 4s first? I've seen it done both ways and I'm getting confused.

Jacquelyn Challis 2B

Thank you so much!!

Jacquelyn Challis 2B

Anyone else keep adding up the points to see how their grade changes every day? Or just me lol.

Jacquelyn Challis 2B

I'm having a hard time understanding some aspects of dipoles as a whole. One thing I'm stuck on is an old sapling question. How do you know this is Dipole-Dipole? Thanks

Jacquelyn Challis 2B

I'm reviewing topics in preparation for the midterm, and I know I'm iffy on determining which bonds are more ionic vs more covalent in character. Any tips on how to figure this out? For example, Sapling question 10 from last week lists: Br-F, F-F, Cl-F, Ca-F, K-F and asks you to put them in order fr...

Jacquelyn Challis 2B

On this same question, it asks for oxidation number of chlorine in the perchlorate ion. What does that mean and how would I find it?

Jacquelyn Challis 2B

So does this mean the midterm will cover up to & including lecture 18?

Jacquelyn Challis 2B

Thank you all very much!!!

Jacquelyn Challis 2B

Okay, I've gotten to the last part of this question where there is a table with bond lengths. I'm not sure what ample & overwhelming bond character mean.

Jacquelyn Challis 2B

The next part of this question asks: "Which of the Lewis structures would be expected to contribute the least to the overall structure of the carbamate ion?" How would I figure out the answer to this?

Jacquelyn Challis 2B

Hi! I've been trying to go back through the lectures to find the formula for formal charge and I can't find it. Based off this post, I think the formula is: formal charge= valence electrons-( (bonds/2) + lone pairs). Is this correct?

Jacquelyn Challis 2B

Hi! I was also struggling to really understand electron configuration, and I found that this link to a Khan Academy video helped a lot: https://www.youtube.com/watch?v=NIwcDnFjj98

Jacquelyn Challis 2B

My all time favorite is Supernatural on Netflix:) Definitely recommend

Jacquelyn Challis 2B

Hi! I had a similar question: Calculate the wavelength, in nanometers, of the spectral line produced when an electron in a hydrogen atom undergoes the transition from the energy level n=6 to the level n=1. My answer is 9.394*10^-8 and I can't figure out why my answer is wrong.

Jacquelyn Challis 2B

Regarding the midterm, can I use a graphing calculator or does it need to be scientific? I can't remember if Lavelle told us this info already or not.

Jacquelyn Challis 2B

Okay for this question I got the answers: from 37.61nm to 12370nm and it is telling me that 37.61nm is wrong, but I don't understand why. Any help would be great!

Jacquelyn Challis 2B

I'm still stuck on this question, I understand the steps but I can't figure out how to find c for the equation E=hc/wavelength?

Jacquelyn Challis 2B

I've been finding that the textbook questions are harder than the Sapling questions/ other practice problems Lavelle show us. Is anyone else feeling this?

Jacquelyn Challis 2B

Lavelle says in the syllabus that doing the textbook problems, doing the Sapling homework, and completing all the modules on his website should prepare you well for the midterm.

Jacquelyn Challis 2B

I think he will probably continue the step up and workshop sessions this week which would probably be some good review before the midterm?

Jacquelyn Challis 2B

Does anyone have any good study tips for this midterm? I've been going back over the book questions for review but I'm not sure what else I should be studying.

Jacquelyn Challis 2B

Does anyone know how many questions will be on the midterm and/or how much time we'll have to complete?

Jacquelyn Challis 2B

Hey, I think I need to start attending step up sessions, do I have to sign up for them? Or do I just go to the zoom link during that time? From what I've heard, you do practice problems... is there a packet I would need to have ready/print beforehand?

Jacquelyn Challis 2B

Lavelle's email said you can also check out/rent webcams from UCLA, which might be cheaper than buying one.

Jacquelyn Challis 2B

Hey, does anyone know if there's a groupme for 1H? Thank you! :)

Jacquelyn Challis 2B

Does anyone know how to create a new post? I only see the post reply button but i can't figure out how to start my own new discussion.

Jacquelyn Challis 2B

I needed a refresher course on molarity as well, and I found that the video under Audio-Visual Focus-Topics titled "Molarity and Dilution of a Solution" on Lavelle's website to be super helpful.

Jacquelyn Challis 2B

I ordered my textbook to be picked up at the UCLA store and got a confirmation that it shipped, but that was almost a week ago. Does anyone know how long it takes for it to be delivered to the UCLA store once it ships?

Jacquelyn Challis 2B

I think I understand the steps in this question, but how do you know if the equation is balanced? Are we supposed to assume it is balanced, and if not how would I go about balancing it?

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