CHEMISTRY COMMUNITY

claire ikemiya_2I

And remember that the oxidation reaction is in the anode and the reduction is the cathode.

claire ikemiya_2I

I will try and give an analogy that helps me visualize this. Think about a very wealthy community. Imagine giving each individual $2000. Now think about a much poorer community. Imagine giving each individual $2000. The money will have a much greater impact on the poorer community than the wealthier...

claire ikemiya_2I

That about covers it!

claire ikemiya_2I

How do you guys go a out determining the speed when given various mechanisms.

claire ikemiya_2I

Due to the fact that I don't recall Lavelle putting any Spaling questions on past exams and that he put a good amount from the textbook, I would prioritize that.

claire ikemiya_2I

Have you asked a TA about this?

claire ikemiya_2I

Dear Kyle Walsh,
Do not fret if you had troubles starting this problem, all you have to do is add 48 and 49. Hope you well on the final tmr!

claire ikemiya_2I

Acid and Bases!

claire ikemiya_2I

I'm taking chem 14BL in summer and chem 14c in spring!

claire ikemiya_2I

When i intially did this i thought n would equal 5 since that's the charge of the equation, but now i am seeing that is wrong. Now realizing n= 2, anyone have quick tricks to figuring out n.

claire ikemiya_2I

Example: First order reaction
rate law: rate = k [A]
integrated rate law : ln[A] = -kt+ ln[A]

claire ikemiya_2I

I will try and give an analogy that helps me visualize this. Think about a very wealthy community. Imagine giving each individual $2000. Now think about a much poorer community. Imagine giving each individual $2000. The money will have a much greater impact on the poorer community than the wealthie...

claire ikemiya_2I

I tried circling it, sorry if its hard to see but on the home page of sapling, where you access textbook. hope this helps.

claire ikemiya_2I

I'm living in an apartment right now and totally love it, but i think i would be nice to be on campus next year especially if class is going to be in person. I have friends in the dorms right now who absolutely love it too, and nothing beats our meal plan.

claire ikemiya_2I

Heres mine too. same concept but i was given an exothermic reaction.

claire ikemiya_2I

I would either spend all day Saturday doing textbook problems or weeks 1-10 of matt, kate, or michaels worksheet from their review sessions or both. The UAs pull the questions on their worksheets from past midterms/finals (although they did not have a 14B final due to covid). But keep in mind Lavell...

claire ikemiya_2I

Yes you do not need values it more just conceptual. If a species is first order, what happens to the concentration of that also happens to the rate. If a species is second order, what happens to the concentration of that is squared to the rate. So as stated above is B is tripled (3^2)=9, the rate mu...

claire ikemiya_2I

Same thing is happening to me too. Someone on my chem community post about it said to add decimal values after (bc i just left it as 2 x 10^-6) so that might work for you too, didn't really work for me though.

claire ikemiya_2I

Does anyone regularly attend Michael's UA review sessions? I'm working through all of his worksheets and cannot figure a question on his thermodynamic worksheet (week 6) out and his answer key doesn't have work. If anybody could help me out that would be amazing.

claire ikemiya_2I

So for example
A + B --> C + D
C + D + E--> B +F

Overall: A + E--> F
Intermediates: C, D
Catalysts: B

claire ikemiya_2I

Another easy way to tell I learned in highschool is that catalysts are on the reactant side of Step 1 and intermediates are on the product side.

claire ikemiya_2I

How can you tell if a reaction is exothermic or endothermic without a reaction profile?

claire ikemiya_2I

in 14A we had a grace period after the final i think to get more posts in but Lavelle confirmed sunday of week 10.

claire ikemiya_2I

I got the same thing as Sid, the exponentials do get tricky and annoying to juggle but just double check u have enough parentheses.

claire ikemiya_2I

Yeah the tests is cumulative from this quarter so i will sadly be redoing every textbook problem from all the outlines

claire ikemiya_2I

Yes, these are important to also show how steep the activation energy is.

claire ikemiya_2I

You can go to any TA, they all have access to our midterms.

claire ikemiya_2I

Has it been announced when Chem community posts are due?

claire ikemiya_2I

To solve this i just plugged in for rate=k[A][B]^2 and used the k i found above and the initial values given in the question and i seem to still be getting the wrong answer...is the something i'm missing? Also I dont know if its the same for everyone but my [C] was a zero order

claire ikemiya_2I

Just make sure
1. You are choosing the right species that are being oxidized/reduced
2. The molecules are balanced
3. Add electrons
4. Add charges onto species (if any)

claire ikemiya_2I

^^ This concept is really important to understand because in Kate's review session she said that on her tests she had to order the strength of reducing/oxidizing power.

claire ikemiya_2I

Where can I find Lavelle's guide to balancing reactions?

claire ikemiya_2I

Do the NO have different charges or different amounts of O molecules?

claire ikemiya_2I

I know it's not supposed to work, but I actually just balanced this equation as normal which got me the right answer. I think as long as charges and molecules are balanced on each side you're good.

claire ikemiya_2I

What general tips/rules/tricks do i need to remember when writing cell diagrams

claire ikemiya_2I

Yes, Potassium cannot be reduced because its oxidation number does not change so it is neither gaining nor losing electrons.

claire ikemiya_2I

On the equation sheet we use Ideal gas, deltaU = 3/2nRdeltaT when there's constant volume, but when theres constant pressure can we use deltaU= 5/2nRdeltaT? Or can we only use the equation given.

claire ikemiya_2I

Whats the general rule/equation for calculating heat required for a phase change? I think in a UA review session they added ndeltaH to q, is that what you guys are doing to or is there another way?

claire ikemiya_2I

when do you use q=mcAT and when do you use q=ncAT

claire ikemiya_2I

Yes we are just looking at moles of gas in the problem!

claire ikemiya_2I

kind of a side question, is 14BL usually offered in summer as well? If so, is it being offered in sess A or C? Yes it is offered during summer, i think that prof got bad reviews on bruinwalk but i would double check. I think doing it over summer might be the best idea since people have said the wor...

claire ikemiya_2I

Why doesn't water effect the equilibrium? I understand the addition of water doesn't have an effect on gases, but since there is an aqueous species doesn't liquid impact that?

claire ikemiya_2I

So for this problem you are given 15.5 g CH3NH3Cl and then you have to convert to moles. I understand once you write the balanced equation you disregard Cl because it does not affect pH but do I still calculate it in when converting to moles?

claire ikemiya_2I

Are you guys taking Chem 14BL or waiting for it to possibly be inperson in the Fall next year? And if so, what are you taking next quarter?

claire ikemiya_2I

How did you guys calculate Kc? I saw the chart had the K value 0.15 and since you reverse the reaction you have to manipulate it by doing 1/K, but thats wrong...so what did you guys do?

claire ikemiya_2I

For part a, how did you guys know the balanced equation is 2A--->B + 2C?

claire ikemiya_2I

So this is a problem from UA Matthew Tran's week 1 worksheet. The number in red is the answer and I can't figure out what is wrong with my work. Any sugguestions?

claire ikemiya_2I

And make sure when you are making your ICE table, you are subtracting X from the product side and adding to the reactant side. This is because when you add to the products the reaction shifts left. Then plug into Kc equation and square roots both sides to find x! Then dont forget to plug x value bac...

claire ikemiya_2I

Hey guys i was wondering what tab Matthew posts his workshop worksheets under because I want to go back and review them. Thanks!

claire ikemiya_2I

Hey! It is the same as calculating concentration.

claire ikemiya_2I

Once you make the ICE table and get an X value, plug it back into your ICE table equations and add those values together to get P-Total. I hope that helps.

claire ikemiya_2I

So far I've only been to Matthew Tran's, Justin Sarquiz's, and Rosa Munoz's, and I love them all! They are all really good at explaining concepts and use past exam questions which i really appreciate.

claire ikemiya_2I

How are the bond angles in this molecule 107?

claire ikemiya_2I

From the review sessions I went to, one example problem the TAs thought would be important to be able to do is draw a lewis structure, then describe IMF, and describe shape/bond angle. So, I think it we need to understand all aspects for the final. Online charts + book examples are really helpful.

claire ikemiya_2I

I really like this visualization!

claire ikemiya_2I

Is the course evaluation the one we were emailed, or can it be found somewhere else?

claire ikemiya_2I

Yes! All elements below row 3 can expand their octet.

claire ikemiya_2I

To find oxidation number you have to look at the overall charge of the compound, charges of the compounds inside of the coordination sphere, and make a formula. For example [Co(CN)5(0H2)]2-, CN has an overall charge of (-1) and (OH2) is neutral so you’d make the equation X+5(-1)+0=-2 And solve for x...

claire ikemiya_2I

Which two oxygen atoms? Is it the ones with the single bonds?

claire ikemiya_2I

So, in a review session I learned that a compound with a larger surface area contains stronger LDF. Translating that to the last topic we learned, would a compound with larger surface area be a weaker acid since it would be harder to give up electrons?

claire ikemiya_2I

Yes, and all Bronsted-Lowry acid/bases are lewis acids and bases, but not all lewis acids/bases are bronsted lowry.

claire ikemiya_2I

How do you determine charge for the d-block elements?

claire ikemiya_2I

anikamenon1L wrote:Did he ever respond to you because I still haven't heard back

No he did not

claire ikemiya_2I

k2s03 is actually basic too. since the anion is derived from a weak acid, it will pull an H+

claire ikemiya_2I

Does anyone know where Andrew Salmon ended up posting the recording to his review session?

claire ikemiya_2I

What is the difference between molecular shape and electron geometry?

claire ikemiya_2I

Do we only have a lecture on Monday this week?

claire ikemiya_2I

I always play it safe and use two places after the decimal point to insure accuracy

claire ikemiya_2I

I also heard a TA say that textbook problems will be most helpful in preparation for the final!

claire ikemiya_2I

I'm pretty sure the answer is no, but one could hope.

claire ikemiya_2I

And if you are ever asked which acid is stronger than another, remember the elements with a smaller atomic radii is stronger since it has a shorter bond with H, which is requires more energy to break.

claire ikemiya_2I

How come hexagonal planar is not a possible geometry for a compound with a coordination number of 6?

claire ikemiya_2I

So if all we know is that 50% is a passing grade, do we project that the passing range is larger or that the grade is going to be curved?

claire ikemiya_2I

Does anyone have any quick.easy methods for calculating oxidation number? thanks.

claire ikemiya_2I

While oxygen is more electronegative, it is not taken into account when comparing all 3 compounds because oxygen is present in each one.

claire ikemiya_2I

95 minutes of 30 questions from the topics covered throughout the course so far!

claire ikemiya_2I

I know that triple bonds are composed of 1 sigma bond and 2 pi bonds and since during Dr. Lavelle’s lecture, he drew one with the 2 pi bonds as the outer bonds and the sigma bond in the middle does that mean they need to be in that order or does it not matter?

claire ikemiya_2I

On #20 the compound [AsO4]3- the structure has 3 single bonds, and 1 double bond. Since the double bond is shorter, why is the shape still tetrahedral?

claire ikemiya_2I

I noticed the previous weekly discussion point section of our grades changed, does that mean they will always update and we just need 50 by the last week?

claire ikemiya_2I

Yes, after you find the number of valance electrons you add bonds and lone pairs to the compound until each molecule has 8 electrons (except Hydrogen only requires 2). Also important to note, the central atom is the least electronegative one. There other exceptions to the octet rule for more complex...

claire ikemiya_2I

On that same note, i do not remember what happens if you want to know which problems you answered incorrectly and was wondering if anyone knew. thx

claire ikemiya_2I

However, there are instances where the resonance structures are equal!

claire ikemiya_2I

I thought I had read somewhere on period 3 elements can expand their valence shells, but on the book work for 2C, the central atom accepted more than 8 electrons, and I was wondering if anyone knew why or if there is a different rule for that?

claire ikemiya_2I

How do you determine the oxidation number of chlorine in the perchlorate ion?

claire ikemiya_2I

We will probably be given a couple of choices of Lewis structures and then asked what is the correct one. Since it's on CCLE, there won't be a drawing feature I'm guessing. Wait is the 2nd midterm also all multiple choice? The second midterm is same format as the first one, but my TA said there's a...

claire ikemiya_2I

Here you go!

claire ikemiya_2I

Increase across a period, decrease down a group

claire ikemiya_2I

Hi, he explains in the lecture on 11/4 that P, S, and Cl are exceptions to the octet rule and can accommodate more than 8 electrons!

claire ikemiya_2I

Definitely email your TA to get the missed material, and if you need more interactive learning stop by either a step up session or workshop. I found them super helpful :)

claire ikemiya_2I

They did that instead of using the Rydberg's equation on our formula sheet because they combined 2 equations. Normally you would do
lamda = c/v and then plug into Rydbergs equation, but they combined it and so the 1.0974 x 10^-7 is R constant divided by speed of light.

claire ikemiya_2I

Hi, I'm still a little but confused on how to tell which numbers you plug into n2 and n1 when you use Rydberg's equation and was wondering if anyone could briefly explain? thanks.

claire ikemiya_2I

Sinusoidal means that a FULL "sin" wavelength has been completed, so the examples that have half a cycle on the end are not compatible (even though they look uniform).

claire ikemiya_2I

Another good thing to keep you eye out for is key words like "observed" so you know right away it is visible light.

claire ikemiya_2I

So to help you with finding the electron, you need to start by finding the velocity using De Broglie's equation (v = h/(m*lamda). Once you get the velocity, you plug it into E = 1/2(m)(v^2) and you are left with the energy of the electron! Hope that helps.

claire ikemiya_2I

Can someone please explain the relationship "AS n --> infinity, E--> 0"

claire ikemiya_2I

To those who are attending the step up sessions/workshops, do you recommend them or is doing the optional bookwork problems enough to understand the curriculum?

claire ikemiya_2I

I understand that when electrons transfer down level, light is then emitted. So does that mean that while the electrons are "excited" and is at a higher energy level is the atom not visible yet?

claire ikemiya_2I

Yes, I also just got an email saying he was going to bundle weeks 2, 3 and 4 all into 1 assignment due the Sunday of week 4.

claire ikemiya_2I

Can someone please explain the difference between the second graphs for the constructive and destructive waves? He went over them in Fridays lecture (10-16-20) but i still am not 100% sure.

claire ikemiya_2I

The link to the answers are on the class dashboard on Sapling/ebook, but they are only odd #. However, the do work through the problems and are extremely helpful!

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