CHEMISTRY COMMUNITY

Sofia Azmat 1I

Whatever you do, do not retake the class. A lot of people end up in trouble later, and I promise you a passing grade is better than retaking it. I know that if you are in the college of letters and sciences, you can only retake up to 3 classes where the new grade you get replaces your old grade, and...

Sofia Azmat 1I

Since the reactant quotient isn't changing, ΔE would be zero at equilibrium.

Sofia Azmat 1I

I think it depends on your TA, but most TAs will give you credit if you have 50 posts by the end. As long as you have 50 points by the end of week 10 you should be fine.

Sofia Azmat 1I

A lot of the spots open up by the second week of classes so you should be fine. What I usually do when I'm in that situation is that I add one additional class to my study list, and if I get off the waitlist for the class I need by week 2, I drop the additional class. That way you aren't in danger o...

Sofia Azmat 1I

I know a lot of people who took 14B and 14BL together but then chose to take 14C and 14CL separately. Personally, I would look at your own schedule and decide if the workload is something you want to take on. If you felt comfortable taking 14B and BL together you might be okay with taking 14C and 14...

Sofia Azmat 1I

I'm leaning towards pre-law and I am a neuroscience major. I would say that if you think medical school is something you might want to do in the future, then it would probably be best to take the required classes anyways. I'm not 100% sure about what I want yet, so I am taking the pre-med classes an...

Sofia Azmat 1I

Think of it as heat gained vs heat lost. When heat is lost by the system it is GAINED by the surroundings, almost like an inverse reaction. When heat is lost by the surroundings it is GAINED by the system. This is of course assuming the system has no outside factors to account for.

Sofia Azmat 1I

Personally, I've learned to not study up until the very last second because it's important to give yourself a break beforehand and a good night's rest.

Sofia Azmat 1I

The reason for my burnout is because I feel like I'm not doing enough work so I end up pushing myself too hard. Give yourself a break, and if you feel like you can't afford to have one it might be when you need one the most. Don't be afraid to ask your professors for help when you need it, especiall...

Sofia Azmat 1I

You are correct, this has to do with equilibrium. Basically what they're trying to get at is that if products aren't removed during the forward reaction, they will end up accumulating and this will kickstart the reverse reaction as a result.

Sofia Azmat 1I

Given that the atom is within and therefore a part of the molecule, you can consider that the whole molecule is oxidized along with the atom

Sofia Azmat 1I

Yes, anodes have to be on the left and cathodes have to be on the right and it also shows the direction of electron flow.

Sofia Azmat 1I

There is a link to the table that you need to solve this problem in sapling. Once you click on the word table it will open a new tab for you and you can get the values you need from there.

Sofia Azmat 1I

I feel a little better knowing that I improved on this midterm, so I feel like I can do good on the final. I am a little worried with the new content we've been learning, but I'm just hoping for the best.

Sofia Azmat 1I

I would post 5 times a week just in case, but the TAs are the ones grading these so I would check in with them. Depending on your TA, they might give points per week or they might just check to see if you have 50 posts in total by the end of the quarter.

Sofia Azmat 1I

The points are capped at 50, but you are still allowed to post as many times as you'd like. If you still have a question later on, you can still ask about it on here you just won't get any extra points.

Sofia Azmat 1I

The loss of electrons is oxidation and the gaining of electrons is reduction. Using either the OIL RIG mnemonic or the LEO GER one we learned in class would be helpful as well. When losing electrons it becomes more net positive, and gaining electrons increases negativity, so that is also important t...

Sofia Azmat 1I

It really depends on what the question is asking you to find. There is constant-volume calorimetry and constant-pressure calorimetry and maybe in the question you're being asked to calculate the change in internal energy or a change in enthalpy. A general assumption you can make is that a calorimete...

Sofia Azmat 1I

You're describing an isochoric process or as you stated, a constant volume process. The formula for work is w=PΔV, and if there is a constant volume, that means there is ZERO change in volume. Because ΔV = 0 , any P value that you multiply it by is going to give you 0 for work. w=P(0) will always me...

Sofia Azmat 1I

A general rule is that, if Q<K, the reaction will favor the products, and if Q>K, the reaction will favor the reactants. When Q=K, the reaction is at equilibrium

Sofia Azmat 1I

Mrudula Akkinepally wrote:Thank you so much!

We can't use that on the midterm right? Like we have to use the one we use every time?

Please let me know! Thank you!

You are allowed to use the equation sheet he posted, just don't add your own notes to it or anything

Sofia Azmat 1I

Calculate the final temperature and the change in enthalpy when 765 J of energy is transferred as heat to 0.820mol Kr(g) at 298 K and 1.00 atm (a) at constant pressure; (b) at constant volume. Treat the gas as ideal. I was able to find the final temperature for part a and part b, but I'm confused as...

Sofia Azmat 1I

We don't know what specific questions from the textbook are going to be included on the midterm, but the syllabus and the outline recommend questions 1, 3, 5, 7, 9, 11, 15, 17, 19, 21, and 23 from the section 4D.

Sofia Azmat 1I

Hi guys, I'm starting to get a little nervous about the second midterm and I've been doing the textbook problems, sapling problems, and reviewing content quite a bit. I didn't do so well on the first midterm and I was wondering if there are any other resources you guys use outside of the class that ...

Sofia Azmat 1I

Is it updated weekly or is it based off the correct amount at the end of the quarter? I remember last quarter it would be updated towards the end since we would just need to have 50 by the end. Does anyone know if this still applies or should I just communicate with my TA. They are checking them we...

Sofia Azmat 1I

I think as long as you post 5 posts per week you should be getting all of your points. I also got a few points missing on mine though, and I kind of just assumed its because if you post under the same post twice, when you look at your posts, that entire thread moves to the top. So they might only be...

Sofia Azmat 1I

I've been feeling nervous about the midterm as well. Sometimes I feel like I have a good understanding of the content, but when I get to the actual problems I can't give step by step solutions to it. I'm not sure why but sometimes practice doesn't feel like enough to me and I don't entirely know how...

Sofia Azmat 1I

Work done on a reversible pathway: carried out in a series of steps and happens very slowly (less heat is being lost to its surroundings). Work done in this process is GREATER than irreversible work, and the process does the MAXIMUM work. Work done on an irreversible pathway: carried out rapidly. Wo...

Sofia Azmat 1I

MT 2 is supposed to cover everything up until Outline 4. We will finish this by Friday's lecture I believe. As of right now I believe we just finished 3 and are working on 4.

Sofia Azmat 1I

My TA looked at this problem while we were discussing it in lab and he said the solution manual had a typo. The part where they calculate the enthalpies using the table isn't correct. I'm not sure if Lavelle has this question on the solution errors pdf on his website though

Sofia Azmat 1I

I saw mine on myUCLA exam and homework grades at the very bottom of the page

Sofia Azmat 1I

For this question, first remind yourself that you are given or you know the values for P, V, R, and T. What you don't know are the moles of gas you have and you need the moles to be able to calculate the work for path A. Use the equation PV=nRT to solve for n, moles. Once you have the n value, plug ...

Sofia Azmat 1I

To solve for part A, try listing what you already know first. You know your values for P, V, R, and T, but you do not know how many moles of gas you have. Use the equation PV=nRT to find the number of moles in this sample. From there, once you've determined the number of moles, use the w=-nRTln(V1/V...

Sofia Azmat 1I

You actually have to use the PV=nRT to find the moles first. You already know the values for P, V, R and T. Once you find the number of moles, you can use the w=-nRTln(V2/V1) formula to find work done.

Sofia Azmat 1I

The different values for R are given to you for different units, and you just have to use the given values accordingly.

Sofia Azmat 1I

Your first goal is to try and manipulate the given chemical equations to get the one at the bottom. You can do this by multiplying each individual equation and/or writing them in the reverse direction as required, just be sure to multiply the enthalpies to the right with the same value and to change...

Sofia Azmat 1I

Equipartition theorem: Energy is distributed EQUALLY along all degrees of freedom, and each molecule in a system has a specific amount of energy (kT) that it gives off with each degree of freedom. Degrees of freedom. The number of independent ways in which an atom or a molecule can exhibit motion, w...

Sofia Azmat 1I

I think there are situations where heat capacities can be negative, but those are more advanced examples applied to very specific situations and you don't need to worry about that for this class. In this class the heat capacities will always be positive.

Sofia Azmat 1I

Hey Lillian! I understand the feeling and I think the most important thing to do is recognize that you're still trying, and that you can't get everything done at once. Some classes are overwhelming and what I like to do is focus on the tasks that are causing me the most stress first especially if I ...

Sofia Azmat 1I

Your goal is to find heat capacity (C). Use the mass of compound A to find the heat given off by the substance (answer will be in kJ, and this will be your Q value). You are already given delta T, the change in temperature. To solve, use the equation Q=CΔT. We already found Q, we were given ΔT, so t...

Sofia Azmat 1I

They will probably be posted some time this week or early in the next.

Sofia Azmat 1I

Increasing volume or decreasing volume has no effect on K. It does, however, have an effect on pressure which is what you might have been thinking of. By decreasing volume, pressure increases when it comes to gases. That is one of the examples Professor Lavelle mentioned during lecture 3.

Sofia Azmat 1I

In class so far we learned that the only factor that affects the equilibrium constant is temperature. Depending on whether your reaction is endothermic or exothermic will determine whether K will increase or decrease.

Sofia Azmat 1I

Any second device would work but a phone would be easiest

Sofia Azmat 1I

The unit that is most accurate is bar, but Lavelle said that we will be using atm instead. They are fairly close anyways.

Sofia Azmat 1I

The same thing was happening to me and someone in discussion mentioned that Lavelle has a link to the pdf on his website, I would check that out :)

Sofia Azmat 1I

so you couldn't have a positive reactant and positive product value, one needs to be negative? As far as I know, yes. One will always be positive and the other will always be negative. To determine which is which, you need to look at what the initial values are as well as what is being lost and wha...

Sofia Azmat 1I

Okay so for this problem you are going to need to know the specific heat for some parts, and I am pretty sure there will be a chart in the textbook that explains them, I completed this earlier so I can share what I did to complete this. Another thing that is important to note is that ice melts at 0°...

Sofia Azmat 1I

Steam would cause more severe burns compared to water at the same temperature because steam contains more of what is known as "latent heat". Latent heat is essentially the heat needed in order to change a solid into liquid or solid/liquid into gas form without changing the temperature. Ent...

Sofia Azmat 1I

Yes! You're allowed a calculator, the constants and equations sheet, and as much blank scratch paper you think you need Would we find the constants and equations sheet somewhere on Lavelle's website or would we just make one ourselves? You will find the equation sheet on his website, you will just ...

Sofia Azmat 1I

Yes. You disregard it because in chem they approximate the answer to 0.142-x to be just about 0.142. This is because the value of x is so small that even if you were to keep x there it wouldn't matter because when you would use the appropriate amount of sig figs you would end up with 0.142 anyways.

Sofia Azmat 1I

I used multiple attempts for some of the chemistry problems on sapling but completed everything and got 100%. Would I be marked down for using multiple attempts? Is it graded for accuracy or just completion?

Sofia Azmat 1I

When you have two positive values, I believe you pick the value that is less than what you see when you look at the initial concentration of the reactants, and reject the value that is greater than the initial concentration of the reactants.

Sofia Azmat 1I

Yes, because the only way you can change equilibrium constants is if you change the temperature of the system. Without this change, the values for Kc and Kp remain constant.

Sofia Azmat 1I

This depends on what you have initially, and what you will end up losing in the reaction. If you are using up more reactant to form the product, you would use a negative sign for the reactants and positive for the products. If the reaction is reversible, look at the arrow between the balanced equati...

Sofia Azmat 1I

I would suggest using the ICE box unless you are certain it is a strong acid/base. They are particularly useful though when you are trying to pinpoint a change in the reaction over time.

Sofia Azmat 1I

The value of Kc can only change if there is a change in temperature. Without a change in temperature, Kc's value does not change.

Sofia Azmat 1I

Yes you will, and sometimes it's more helpful to see multiple replies to a post so you kind of find an answer that can help you more. Different phrasing/ more in-depth or simplified answers can be easier to understand for some people so you're fine if you do decide to post something similar to a pre...

Sofia Azmat 1I

Q is the reaction quotient and K is the equilibrium constant. When the reaction is moving forward, reactants are being converted into products, whereas when it is moving in reverse, products are being converted into reactants. So basically the quantity that is being represented by Q changes when the...

Sofia Azmat 1I

Are those a part of our grade?

Sofia Azmat 1I

Yes. Also just to add on to the previous post, if you are not given molarity in the question itself for your initial values and you are instead given something like moles/L, you are required to convert them to molarities before inputting them into your ICE chart. And also if instead of Kc you were l...

Sofia Azmat 1I

When I purchased sapling from the UCLA store last year, they did not send me an access code in my email but they mailed me a receipt instead... if you have not gotten an email from them by now they are probably going to mail you a letter with an access code on the back. Sapling allows you to access ...

Sofia Azmat 1I

If you want a more "step-by-step" way to solve it, or a more formulaic method to solve it you could also try using what's called an ICE chart. There are a couple things you already know just from the question: 1. You know the INITIAL amounts for N2 and H2 (0.250 M and 0.500 M respectively)...

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