CHEMISTRY COMMUNITY

Mackenzie Fernandez 3G

hi!

I think you just have to know the rate law graphs and how to construct a reaction diagram (I think that's what it's called)

hope this helps!

Mackenzie Fernandez 3G

hi!

I thought that any and every reactant (as long as it is not an intermediate or solvent) could be included in the rate law.
someone correct me if I'm wrong! (I am not sure)

Mackenzie Fernandez 3G

hi!

I thought that you could use either "bar" or "atm" when it came to calculating with pressures.
someone correct me if I'm wrong!

Mackenzie Fernandez 3G

hi!

Some things that I usually double check for these problems:

1) did I use ln
2) did I remember to account for any 10^x
3) did I use the correct conversion (1000 J = 1 kJ)
4) did I remember to cancel out/include negatives

hope this helps!

Mackenzie Fernandez 3G

hi!

I have heard that using Pt is only for situations when no other solid is present in a given reaction. Not sure if this is 100% accurate though.
would appreciate someone clarifying this!

Mackenzie Fernandez 3G

hi!

I have heard the general rule is: add Pt(s) when no solid is available in the given reaction. I am not sure if this is 100% accurate though.
would appreciate someone clarifying this!

Mackenzie Fernandez 3G

hi!

do you mean the notation where its like ||

if so, then the || is equivalent to the salt bridge
and | is just to show that there are substances in different states (aq or s).
you always have the || dividing the anode and cathode

hope this helps!

Mackenzie Fernandez 3G

hi!

what is the significance of linearity in graphs? I still don't understand the concept. Also, is the general rule: for a reaction to be "x" order, the graph must be linear??

thanks in advance!

Mackenzie Fernandez 3G

hi! I am a bit confused on what exactly constitutes a slow or fast reaction. Are we basing this solely on a numerical value? Or will we always have to look at a reaction and think which reactant will determine the "speed" of a reaction? any and every interpretation is appreciated. thanks i...

Mackenzie Fernandez 3G

hi!

I think k' is only referring to the overall reaction and when there are multiple reactants. I am not quite sure if Lavelle reviewed how to find k from k' in lecture.
would appreciate someone explaining this!

Mackenzie Fernandez 3G

hi! I really like handwritten notes. I have been using the same chemistry notebook for Chem 14A and Chem 14B so it really helps me when I need to review concepts that are present in both classes. I do like to print out worksheets from step up sessions and workshops though, because sometimes writing ...

Mackenzie Fernandez 3G

hi! I have also heard mixed reviews. One thing that seems to be consistent is that if you like biology, org chem will be easier?? not sure if this is true. But I think it really depends on how you think problems through. Some people get ochem right off the bat and some don't. But don't feel discoura...

Mackenzie Fernandez 3G

hi!

I believe this has to do with the fact that the transfer of electrons corresponds with the transfer of mass. When the electrons move to the Y electrode, the specific element builds up on the electrode.

hope this makes sense!

Mackenzie Fernandez 3G

hi

I was also wondering if someone could provide a quick explanation as well!!

thanks in advance!

Mackenzie Fernandez 3G

hi!

I think when writing a cell diagram notation, the coefficients do not matter as we really want to know the general position.

someone correct me if I'm wrong!

Mackenzie Fernandez 3G

hi!

I think this just has something to do with wanting to find the speed of the specific reaction (kinetics).

someone correct me if I'm wrong!

Mackenzie Fernandez 3G

hi!

I don't know if this is correct, but I associate being able to oxidize something with size of the element. So the larger the element, the better it is at oxidizing and giving e- away.

someone correct me if I'm wrong!

Mackenzie Fernandez 3G

hi!

We should so make a Chemistry Spotify Playlist!!
I love Colony House <3
https://www.youtube.com/channel/UCBUF-M ... m4ziKfGp4A
(YouTube ^^)

Mackenzie Fernandez 3G

hi!

I am a part of Bruins Fighting Pediatric Cancer (BFPC), Association of Chinese Americans (ACA), Bruin Medical Review, Life Science Student Association, and CURE!

Mackenzie Fernandez 3G

hi!

I found this post on Research Gate. Hope it helps!

https://www.researchgate.net/post/What_ ... _and_Pt111

Mackenzie Fernandez 3G

Problem 5G.17 from the textbook says, "Depict the progress of the reaction graphically for the reaction in Exercise 5G.13." The reaction it is referring to is I2 (g) ----> 2I (g). The solutions manual shows I as the reactant and I2 as the product; is that because we determined in 5G.13 th...

Mackenzie Fernandez 3G

hi!

I do not think this is an equation we need to concern ourselves with as Dr. Lavelle didn't mention this in lecture. It would probably be helpful to keep in the back of our minds, though.

hope this helps!

Mackenzie Fernandez 3G

hi!

I am not sure if this is right, but I believe Dr. Lavelle was generalizing the previous solutions and categorizing them as galvanic cells, as they changed chemical energy to electrical energy. (if someone could clarify this)

Mackenzie Fernandez 3G

hi! I believe this has to do with the fact that the transfer of electrons will result in highly positive and highly negative beakers. The salt bridge helps balance out the beakers by taking ions such as Cl- in a reversed flow. This lets the redox reaction continue for a period of time (I am not sure...

Mackenzie Fernandez 3G

hi!

I believe there is a problem with ATP somewhere in the last outline (4). Also, they aren't really mathematical calculations, but there are some easy questions about isolated, closed, and open systems in outline 3 that connect to real world examples.

hope this helps!

Mackenzie Fernandez 3G

I will be taking Chem 14C, my language requirement class, a major course and two minor courses. I decided against taking Physics 5A. I was told that taking it without prior physics knowledge, and with 14C, would be horrible.

hope everyone is able to get the courses they want for next quarter!

Mackenzie Fernandez 3G

hi!

I am having trouble understanding the concept behind the curve for #20. I understand the equilibrium and how Q and K relate to each other, but what role does spontaneity and Gibbs free energy play? Could someone clarify the connection between the concepts?

thanks in advance!

Mackenzie Fernandez 3G

hi! So for this question you can associate most ordered with the highest deltaS value. So the values you previously calculated can be used to help determine this. I think this question is asking for which of the samples has the most disorder, since deltaS tells you entropy (disorder in a system). Th...

Mackenzie Fernandez 3G

I am currently re-watching Good Omens on Amazon Prime. I find the plot and characters hilarious :)
hope this could bring people some good vibes for the midterm this week!

Mackenzie Fernandez 3G

hi!

I am trying to solve for #18 on this week's homework but I cannot remember how to cancel out ln in an equation.

Can someone help me?
thanks in advance!

Mackenzie Fernandez 3G

hi! For one of the step up sessions, a question asked: "Initially a sample of gas at 412K occupies 12.62L at 0.6789 atm. The gas is allowed to expand to 19.44 L by 2 pathways (assume gas behaves as ideal gas." I had trouble with the second pathway. "B) isothermal, irreversible expansi...

Mackenzie Fernandez 3G

hi!

I agree with the previous statements. kB is just a constant that follows the log rules. You don't really need to do anything to it, just remember how it fits into the whole equation when you multiple everything out.

hope this helps!

Mackenzie Fernandez 3G

hi!

I was wondering if someone could clarify what all the different C equations are. I know that Cs is specific heat, but what are the other significant equations we need to know/are there any others we need to know??

thanks in advance!

Mackenzie Fernandez 3G

hi! I think this has something to do with the one restriction being constant pressure. Also, since the piston is sealed, there is no place for the new material to escape and I think unless it is stated that the piston is physically pushed back, it cannot be moved and the change is irreversible. hope...

Mackenzie Fernandez 3G

hi!

I also find things like lists and organizing helpful. Whenever I don't feel like doing work, I try and set a goal for myself. Normally I try and get at least a half hour of work done and then take a break. It slowly gets better and helps motivate me when I'm down.

Mackenzie Fernandez 3G

hi!

I agree with the above statement. But just some general rules for isolated systems:
1) no interaction with the surroundings
2) normally insulated (like a thermos)

hope this helps!

Mackenzie Fernandez 3G

hi! I had a quick question about 4A5 part b. "A piston confines 0.200mol Ne(g) in 1.20 L at 25C. Two experiments are performed. (a) The gas is allowed to expand through an additional 1.20 L against a constant pressure of 1.00 atm. (b) The gas is allowed to expand reversibly and isothermally to ...

Mackenzie Fernandez 3G

I was wondering if it was possible to post somewhere how the outlines correspond to the lectures and topics covered. I know the general concepts correlate with the outlines, but for specific sections would it be possible to tell us which lectures they align with? (or is something like this available...

Mackenzie Fernandez 3G

I definitely recommend taking Chem 14BL as soon as you can. I find that it helps to take 14B and 14BL either together or as close as you can take them.

Hope this helps!

Mackenzie Fernandez 3G

I definitely took advantage of my weekend. I watched some movies with my sister and treated myself to a very nice serving of popcorn today.
Back to the grind tomorrow! Hope everyone is having an especially restful weekend!

Mackenzie Fernandez 3G

hi!

I think it depends on what you are given for the problem, but I thought I remembered Dr. Lavelle saying the third method was the most accurate.

Mackenzie Fernandez 3G

hi!

I think during Friday's lecture, Dr. Lavelle goes over the calculations and how you always end up with kJ/mol. (someone correct me if I'm wrong.)

Mackenzie Fernandez 3G

Hi! Are we supposed to know the standard states of molecules? Or just some of the most common ones? Or will they be given to us? hi! so someone else said "Dr. Lavelle said that we would not be focusing on standard states that much with regards to calculations. So you probably won't have to wor...

Mackenzie Fernandez 3G

hi! So the problem says: "NH3 is a weak base ( K_{b} = 1.8×10−5 ) and so the salt NH4Cl acts as a weak acid. What is the pH of a solution that is 0.061 M in NH4Cl at 25 °C?" I set up my equation: NH_{4}Cl + H_{2}O \Leftrightarrow NH_{3} + H_{3}O^{+} I then set the respective parts for the ...

Mackenzie Fernandez 3G

hi! So the problem says: "HClO is a weak acid ( K_{a} =4.0×10−8 ) and so the salt NaClO acts as a weak base. What is the pH of a solution that is 0.088 M in NaClO at 25 °C?" I set up my equation: ClO^{-} + H_{2}O \Leftrightarrow HClO + OH^{-} I then set the respective parts for the ICE box...

Mackenzie Fernandez 3G

hi! I am trying to do 6D5 and 6D7. When I look at the solution manual, the K_{b} , K_{a} are somehow found. Could someone explain how these values were derived? Or if they were from some chart in the textbook? (If so, will there be problems like this on the midterms/final and will we be expected to ...

Mackenzie Fernandez 3G

hi!

I had a quick question. I am not sure if this was already explained, but does it matter which section we post under?
Like if we accidentally post in the Chem 14A section will it not count towards our total posts?

thank you!

Mackenzie Fernandez 3G

Why does adding heat to an exothermic reaction favor the formation of reactants? hi! I think this has something to do with the fact that when you break something apart it releases heat. An exothermic reaction is when heat is released. So I think this means if you have an chemical reaction described...

Mackenzie Fernandez 3G

hi! I like to think of like this: whichever thing is being used or is mentioned to be used in the problem, you are subtracting from the overall chemical equation. This helps point to whichever side of the equation will have values of -X. This in turn also tells you which things are being produced, s...

Mackenzie Fernandez 3G

hi!

I usually walk around campus with my roommate (since we're down in Westwood).
I also like to hula hoop. Super easy and fun! Helps trim your waist down :)

Mackenzie Fernandez 3G

hi!

I had a quick question about $K_{w}$
When do we need to use it? I know Dr. Lavelle used it for lectures this week, but could someone lay out the rules for when we use $K_{w}$ specifically?

thank you!

Mackenzie Fernandez 3G

16. 1.50 mol PCl5 is placed in a 500 ml reaction vessel and decomposes at 250°C to form PCl3 and Cl2. KC = 1.80, all substances are gases at 250°C. What is the composition of the equilibrium mixture? hi! I attempted this from the audio visual topics but I can't seem to get the correct answer. could ...

Mackenzie Fernandez 3G

hi!

could someone explain how they did #30 for Part 2 of the Chemical Equilibrium Review?
I was able to get the answer but I don't think I did the steps right.

I did K = $\frac{CO H_{2}}{H_{2}O}$

thank you in advance!

Mackenzie Fernandez 3G

hi!

could someone explain this problem please? I attempted it and did

K = $\frac{1}{BrCl^{2}}$

and plugged in 3.37 x 10 -5 for BrCl but didn't get anything close to the provided answers.

thank you in advance!

Mackenzie Fernandez 3G

hi! could someone explain how they did 23 for Part 2 of Chemical Equilibrium Review? I did \frac{SO_{3}}{SO_{2}O_{2}} (with SO3 to the power of 2 and SO2 to the power of 2) I plugged in 5.0 M for SO3, 5 x 10 -4 for SO2, and 2 x 10 -4 for O2 I put it was not in equilibrium and favored a reverse react...

Mackenzie Fernandez 3G

hi! I had a question on #19 from the Part 2 Chemical Equilibrium review. I kept getting different answers than those provided. Could someone tell me what I did wrong? So for my equation I did \frac{H_{2}}{AsH_{3}} (with H2 to the 3 power and AsH3 to the 2 power) then I plugged in 1.23 x 10^{-3} and ...

Mackenzie Fernandez 3G

Hey everybody. I'm trying to enroll into Sapling but i keep getting an error message pop-up saying I have to sign up for this through my instructor's course on my University's learning management system. This even happens after I clicked on the Sapling link on the CCLE page. Is this happening to an...

Mackenzie Fernandez 3G

hi! for the outline, one of the questions 5G11 asks: "Write the reaction quotient Q ". I am not sure if this is covered in 5G.3/5G.4 or if it was briefly mentioned in lecture, but could someone tell me what this is? Is this just another name for the equilibrium constant K? (I was able to g...

Mackenzie Fernandez 3G

hi! I agree with everyone who has previously posted! I am definitely going to try and do textbook problems more thoroughly and pace myself along with the topics covered in lecture. I also found step up sessions and workshops extremely helpful! So I will definitely continue going to those if they are...

Mackenzie Fernandez 3G

I just wanted to say thank you to Dr. Lavelle, the UAs, the TAs, and everyone who helped make this class what it is! Thank you for helping us students learn! I know times are especially trying right now, so I just have to say thank you again for being so accommodating and giving us so many resources...

Mackenzie Fernandez 3G

I feel so liberated after the final!!!
Wishing everyone the best during the rest of finals week <3

Mackenzie Fernandez 3G

hi!

I find it best to keep my notebooks when it comes to a series-type class. However, I heard that you don't need to retain that much for the chem series?? could someone confirm/deny this?

Mackenzie Fernandez 3G

hi!

I am having trouble finding notes for when to place "ate" and "ic" at the end of names. When do we use these??

thank you!

Mackenzie Fernandez 3G

hi! my lectures keep buffering as well. Originally I went to watch the lecture on Monday, but it wouldn't play so I waited until the next lecture would be posted to see if the issue was resolved. I went in to watch the lectures today and same thing happened :( Is there another platform that the vide...

Mackenzie Fernandez 3G

I understand how to solve for pH. But I am having a hard time conceptualizing the significance of the presence of protons (H+) in solutions? Why is knowledge of pH important and what makes a highly acidic/basic solution special? hi! so I think knowing how many H+ are present helps when determining ...

Mackenzie Fernandez 3G

hi!

correct me if I'm wrong, but I think this has to do with prefixes?? If the element is Cl2 I think this would be read as dichloride?? So a singular Cl is just chloride?

Mackenzie Fernandez 3G

hi! I was wondering if someone could explain one of the points Dr. Lavelle mentioned in lecture. I am still a bit confused. One of his slides said: "Atoms more readily lose H+ if the resulting anion is stabilized by resonance and/or electron withdrawing atoms delocalize and stabilize negative c...

Mackenzie Fernandez 3G

hi!

I was wondering if anyone had any tricks or tips for memorizing/knowing the general area for metals/nonmetals/metalloids on the periodic table??
thank you!

Mackenzie Fernandez 3G

What should you do if no one laughs at your chemistry jokes?

Keep telling them until you get a reaction.
:)

Mackenzie Fernandez 3G

hi!

I also have the same question. I was thinking that there would be some other factors given to us, such as number of lone pairs, that would help us determine between shapes.
Hope someone can clarify!

Mackenzie Fernandez 3G

hi!

I was wondering if someone could explain the seesaw thing Dr. Lavelle mentioned in lecture. I don't really understand the concept.

thank you!

Mackenzie Fernandez 3G

hi! I am a bit confused on this as well. I was thinking along the lines of the number of bonds/lone pairs the atom has. so when you mark the electrons within sp/sp2/sp3 you should be reflecting how many bonds and lone pairs there are. So two arrows would mean a lone pair and one arrow would mean a b...

Mackenzie Fernandez 3G

hi!

So I ran into the same issue. When I attempted this problem I automatically got the S attached to two O with double bonds. And I remembered that double bonds are 1 sigma and 1 $\pi$ bond, so my answer was 2 sigma and 2 $\pi$ . This may just be a case of either answer is correct??

Mackenzie Fernandez 3G

Happy Thanksgiving!

My family doesn't take part in any special traditions, but we do make an old family recipe ham :)

Hope everyone's holidays are going well!

Mackenzie Fernandez 3G

hi!

I have really enjoyed reading this thread :)
I try to treat myself to my favorite dessert or take out. I also like to relax for a good two hours after if I can help it. This includes no homework, classwork, or even looking at my laptop.

hope everyone is having a great weekend!

Mackenzie Fernandez 3G

hi!

I have heard that you will get into the class eventually.
Don't know if someone can confirm this??

Mackenzie Fernandez 3G

thought some positivity could be put out there!!

I found this quote from Jimmy Dean and I love it:

"I can't change the direction of the wind, but I can adjust my sails to always reach my destination."

You guys will totally get through this! <3 Hope you all have a great weekend!

Mackenzie Fernandez 3G

https://sciencenotes.org/periodic-table-trends/

hi!

I also found this website helpful!

Mackenzie Fernandez 3G

hi!

I will be taking both next quarter. I heard from friends that took it virtually that it was not bad. They said if you want to take it separately that is fine, you just have to remember the key concepts from 14B for BL.

hope this helps!

Mackenzie Fernandez 3G

hi!

so when I talked to my NSA they recommended taking these two together. I am not sure what other people are doing, but I plan to take them both next quarter.

Mackenzie Fernandez 3G

hi! As long as you post before midnight Sunday for the respective week it counts for that week. So posting 11/14 - 11/15 before Sunday at midnight counts for Week 6.

Mackenzie Fernandez 3G

Hello, I was having trouble with identifying the difference between a Lewis base and Lewis acid for sapling problem 6 in weeks 5. How do I figure out what is what when given a formula like BeCl2 for example ? so I have in my notes that a LEWIS acid accepts the e- pair from another atom. LEWIS base ...

Mackenzie Fernandez 3G

hi!

so the orbitals are the s, p, d, and f.
the subshells are the varying number of electrons that can be present in the orbital
s = 2 e-
p = 6 e- (3 sets of 2)
d = 10 e- (5 sets of 2)
f = 14 e- (7 sets of 2)

Mackenzie Fernandez 3G

First off, I just want to say that I appreciate the video lectures and the Bruin Cast team this quarter. <3 The added touch of "being" in the classroom and the music in the beginning of each lecture has made my fall quarter feel somewhat normal :) I was just wondering if the Bruin Cast tea...

Mackenzie Fernandez 3G

When I'm drawing the Lewis structures in Sapling homework, I have trouble determining which atom in the molecule to add the positive/negative charge. How do I assign formal charges given a polyatomic ion? Do I use the number of electrons in the periodic table to find which atom has the charge? hi! ...

Mackenzie Fernandez 3G

hi! Will we need to memorize the specific electronegativity for each element? In Dr. Lavelle's lecture he referenced a table/chart with some of the elements and their values. Will we be able to reference a chart like this for future tests or should we just be able to tell whether two elements will h...

Mackenzie Fernandez 3G

hi! I think what you are referring to is when Dr. Lavelle does the formal charge of an atom (minus sign on a specific element) compared to the charge of a molecule overall when drawing a lewis structure (minus sign outside of molecule)? So I think when we are asked questions about this, they will sp...

Mackenzie Fernandez 3G

hi!

I have in my notes that P, S, and Cl can accommodate more than 8 valence e-. These atoms in period 3 or higher have d-orbitals in their valence shells that are able to accommodate these additional e-. I think this can just be summed up to the fact that they are exceptions to the octet rule.

Mackenzie Fernandez 3G

hi!

I also think this has to do with the octet rule!

Mackenzie Fernandez 3G

43. In the hydrogen atomic spectrum, what is the wavelength of light associated with the n = 2 to n = 1 electron transition? I tried to find the wavelength by using the equation v= R [1/(n1)^2 - 1/(n2)^2], and then plugging in the value for v in wavelength = c/v, but the answer I came up with was n...

Mackenzie Fernandez 3G

Here is my question on number 23. The electron affinity of thulium has been measured by a technique known as laser photodetachment electron spectroscopy. In this technique, a gaseous beam of the anions of an element is bombarded with photons from a laser. Electrons from the anion are then ejected a...

Mackenzie Fernandez 3G

hi!

I heard that there was an error found in one of the problems so it might take a bit longer to sort through everyone's tests.

Mackenzie Fernandez 3G

hi! I also think that Schrodinger's and the repulsion of electrons helps determine this shape. I also think it depends on the number of electrons present.

Mackenzie Fernandez 3G

noelle_lipschutz_3F wrote:How was the Heisenberg uncertainty principle derived? I am still so fascinated how humans can derive these equations…

hi! I think Dr. Lavelle talks about this in the module for Heisenberg. If not, he goes over the fundamental principle behind it in lecture.

Mackenzie Fernandez 3G

hi! For one of the sapling questions, it asks: "Considering that microwave ovens radiate at 2.45 GHz, how would you respond to the debate?" How do you convert the GHz so that you are able to solve this equation? The Sapling "Solutions" tab did not elaborate on how to convert this...

Mackenzie Fernandez 3G

How do we differentiate what n1 and n2 should be if the question doesn't state it directly? I know that emitted means that it is going back down to the ground state and absorbed means that the particle is excited. Can anyone explain this further? hi! I think 1A15 is a good example for this! I belie...

Mackenzie Fernandez 3G

Lea Ozdere 1A wrote:For sig figs are we supposed to round or truncate? Or can we do either? For example if an answer is 2.7187 and it should be with 4 sig figs, would that be 2.718 or 2.719?

hi!

I always round. I am not sure when truncating would apply in chemistry (I would ask a TA).
So my answer would be 2.719.

Mackenzie Fernandez 3G

hi!

My TA told me that the midterm would be ~10 questions (about 5 mins per question), all multiple choice.

Mackenzie Fernandez 3G

oh I see, thank you!

Mackenzie Fernandez 3G

hi! I am working on 1.A.9 and I am not getting the same answers as the Solutions Manual. I am using the equations 1) E = \frac{hc}{\lambda } and 2) \lambda = \frac{c}{v} . Then I just plug in the values that are in the table and solve (including converting). For the second row I plugged 3.3 x 10^{-1...

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