CHEMISTRY COMMUNITY

Hailey Kang 2K

Salt bridges are represented by a double solid line like this II

Hailey Kang 2K

I think a lot of classes will hopefully be in person. Some of the larger lectures might still be remote though unfortunately.

Hailey Kang 2K

I use handwritten notes!

Hailey Kang 2K

These are amazing thank you so much for sharing!

Hailey Kang 2K

Correct! Intermediates will never appear in the rate law. However, I believe it is possible for catalysts to appear in the rate law.

Hailey Kang 2K

Hi! For this one you can just pick a value of 1 for A and B and see what happens to each. For example, if the first-order reaction of A is halved, the reaction rate will change by a factor of (1/2)^1. If the second-order reaction of B is tripled, B will change by a factor of (3)^2. This means that y...

Hailey Kang 2K

Hi! I think if you use your method but make sure to flip the same reaction, you should get the same answer!

Hailey Kang 2K

kJ /mol !

Hailey Kang 2K

One you've balanced the half reactions you just have to look at how many electrons ended up being transferred. That number will be your n value!

Hailey Kang 2K

Hi! This question is basically asking about the stability of benzene as a resonance structure versus the stability in terms of just double bonds and single bonds. The bond enthalpy for a carbon carbon bond in resonance structures is a different value than a C-C double bond or single bond. The proble...

Hailey Kang 2K

Organic chemistry tutor has definitely been a life saver.

Hailey Kang 2K

Hi! Concentration cells are not always at equilibrium. Basically, the cell is working to dilute the more concentrated cell, and concentrate the more diluted cell until it reaches equilibrium, which creates a voltage.

Hailey Kang 2K

Hi! Adding on to the post above, it depends on whether each equation is dependent on initial concentration or not. This is obtained from the integrated rate law.

Hailey Kang 2K

Hi! The textbook has a really good explanation on how to do it. I would also recommend going to a UA session if you're still unsure and asking them to help explain it!

Hailey Kang 2K

The overall order is determined by adding up the orders of all the elementary reactions!

Hailey Kang 2K

Hi! Your half reactions are going to be Zn2+(aq) + 2e– → Zn(s) and Au3+(aq) + 3e– → Au(s).

Hailey Kang 2K

Hi! When you're balancing reactions in basic conditions, the process is a little different. First you need to split the reaction into the half reactions. Then for each reaction, you balance all the oxygens by using H2O. Then, you balance the hydrogens by using water, and how many ever waters you add...

Hailey Kang 2K

Hi! You can only add H+ if the problem states that it's occurring in acidic conditions. If this is the case, you will first use H2O to balance the oxygens, and then use H+ to balance the hydrogens. For the second question, you always add electrons in order to balance the charges. Once you find the c...

Hailey Kang 2K

This happened to me as, well but when I logged out and refreshed everything it worked for me again!

Hailey Kang 2K

I believe by definition G is the maximum amount of non-expansion work that can be done at constant temperature and pressure!

Hailey Kang 2K

Hi! You put Pt on any side that is missing a conducting solid, so that it can act as one!

Hailey Kang 2K

Molar heat capacity refers to the number of moles, and specific heat capacity refers to the mass in grams!

Hailey Kang 2K

Hi! TM oxidation numbers need to be calculated based on the other elements in the compound!

Hailey Kang 2K

I think it's just a way to confirm that we know how to calculate it in a few different ways!

Hailey Kang 2K

Hi! Here is my work to go along with the steps that previous people have posted. Hope this helps!

Hailey Kang 2K

Hi! Basically, we know that the water took 30 min to get to the final temperature. That means that once the ice has turned into the initial temperature of the water, it will also take 30 min to reach the temperature. Therefore, we only consider the time it took for the ice to actually turn to water ...

Hailey Kang 2K

Hi! The steps that everyone has posted are correct, and here is my work to hopefully clarify more!

Hailey Kang 2K

Hi! Here's my work for this problem - hope it helps!

Hailey Kang 2K

Hi! All the molar heat capacities will either be given in the problem, or available to reference on the constant & equations sheet.

Hailey Kang 2K

Hi! You just have to add 273.15 to your C value to get Kelvin! It's on your equation sheet as well :)

Hailey Kang 2K

Yes!!

I started a document with some of the equations and it's in the shared google drive. Anyone can add to it with any more equations we've learned! :))

https://drive.google.com/drive/folders/1-iUlSUXyOWLHC5chqYRLC2ODsKNCF5fe

Hailey Kang 2K

Hi!

I believe your value for the enthalpy of formation for water should be -285.83!

Hailey Kang 2K

Hi! Yes, for this equation for work, the P is referring to external pressure.

Hailey Kang 2K

Hi! It all depends on what is given in the problem. Usually the first thing I look at is the units of pressure. If there is no pressure given, I will go with the R value that has no pressure in the units!

Hailey Kang 2K

I definitely think studying the Sapling questions are a good tool for exams. After you complete the problem it gives you a detailed explanation how they got to the answer that can help aid your understanding as well!

Hailey Kang 2K

Hi! Here's how I worked it out.

Hope this helps!

Hailey Kang 2K

Hi! I definitely think that, as boring as it might be at times, reading the textbook really has been the most helpful thing for me. There are a lot of great explanations in there! UA sessions are also extremely helpful with further explanations.

Hailey Kang 2K

Hi! If one is constant that does not automatically mean the other is constant. You will have to look at the information explicitly stated in the problem.

Hailey Kang 2K

Hi! The homework is due this Sunday. If it says 65% that just means you've completed 65% of the assignment!

Hailey Kang 2K

Hi! You can always tell which R constant to use based on the units. If you match up the units given in the problem to the R constant, most (if not all) of the units should cancel out!

Hailey Kang 2K

Hi! Because a system has to do work in order for expansion to occur, it is losing a certain amount of energy to do this work. That's why the w would have a negative sign!

Hailey Kang 2K

Hi! When you reverse a reaction, K becomes the reciprocal, so you would calculate 1/K.

Hailey Kang 2K

Hi!

Homework is due this coming Sunday. Using hints from Sapling doesn't take any points off so that's definitely a good resource as well as the textbook! Good luck on the midterm!

Hailey Kang 2K

Hi! Here is the work I did for 15. Hope this helps!

Hailey Kang 2K

Hi!

This will work for your weak acid calculations.

Hailey Kang 2K

Hi!

This has happened to me before, so I use the pdf version of the solution manual! If you go on the sapling page and click on the link that says Atkins, it's a pdf file and that always works. The solutions also have more detailed explanations on how they got to the answer so it's super helpful!

Hailey Kang 2K

Hi!

I remember hearing that tomorrow will be the cutoff for the midterm 1 material. I'm sure next weeks information will be useful, but not necessary for this midterm!

Hailey Kang 2K

Hi! There's an updated constants & equations sheet on his website and I would have the period table as well!

Hailey Kang 2K

Hi! The general rule of thumb is if it is smaller than 10^-4. If you think it's safe to assume that x is 0, but aren't sure, you can always calculate the percent ionization (which is (concentration/initial concentration)(100%)) after you find the concentrations. If the percent ionization is less tha...

Hailey Kang 2K

Hi!

Discussion sections still take place unless yours is this coming Monday.

Hailey Kang 2K

Hi!

I don't think we have to worry about that for this unit at least. One of the UAs went over it in their session, but it isn't super relevant for now.

Hailey Kang 2K

The only things that are graded in this class are chem community, Sapling, and the exams! Everything else is just for your benefit.

Hailey Kang 2K

Hi!
In terms of solving the problem, I would probably agree with the people that have already posted. But on a side note, #7 actually isn't in the list of problems he assigned us to do so we might not even be expected to know this exact problem!

Hailey Kang 2K

Hi!

I would imagine that that was probably a calculation error. I think the numbers on sapling are different for everybody, but at least for mine, I didn't end up getting any negatives under the root!

Hailey Kang 2K

Hi!

I think Dr. Lavelle mentioned during lecture that not too many concepts from 14A would carry over. I've heard 14B has more calculations!

Hailey Kang 2K

Hi!

M refers to molarity which is the same thing as mol/L

Hailey Kang 2K

Hi!

If you get 2 positive numbers, you should omit the one that is larger than any of the given initial conditions. Generally, you will use the smaller positive number.

Hailey Kang 2K

Hi!

You need to access Sapling through CCLE in order for it to work. In terms of the code, if you purchased multi-term access, they should have sent you 2 codes (one that you can enter for this quarter).

Hailey Kang 2K

Hi!

During 14A, they were only posted for the first unit. I'm assuming this it just because of time and because Dr. Lavelle is giving us a chance to get ahead before the quarter starts.

Hailey Kang 2K

Definitely something that worked for me this quarter was going to all the UA sessions, so that's one thing I will continue next quarter! Also like you said, utilizing the textbook and reading all the information there :)

Hailey Kang 2K

Hi! A simple way to look at the trend is that metalloid band plus a few more atoms around it will form amphoteric compounds. If it's difficult to tell based on this, you will need to look at if it can accept as well as donate a proton.

Hailey Kang 2K

Hi! Only one of the lone pairs can bond to a central atom.

Hailey Kang 2K

Hi! Electronegativity increases up and to the right. Therefore, Cl will be higher. Also, electronegativity refers to the atom's tendency to attract electrons. Since Cl has 7 valence electrons, it really wants to attract one to complete its octet. This means electronegativity will be higher.

Hailey Kang 2K

Hi!

This is possible because when the principle quantum number is n=6, all the l values can be 0-5. l=3 means the f subshell, which is where you would get the 6f.

Hailey Kang 2K

Hi!
The main elements we definitely have to know for this class are P, S, and Cl. Other than that, anything with a d-orbital can have an expanded valence.

Hailey Kang 2K

The coordination number just refers to the number of points at which ligands are attached to the central metal atom!

Hailey Kang 2K

Hi! Everything with polydentate ligands is considered a chelating compound.

Hailey Kang 2K

The hybridization is sp3 because there are 4 regions of electron density (3 bonding pairs and 1 lone pair). 4 regions of electron density corresponds to sp3 hybridization.

Hailey Kang 2K

Hi! The composition of the bonds would be the bond all together. So for example in this structure, there's a C single bonded to an H. The composition of this bond would be sigma(H1s, 2Csp2) because the carbon has 3 regions of electron density. The lone pair is strictly referring to that lone pair. S...

Hailey Kang 2K

Hi!

The name of the compound should be pentaamminechlorocobalt(III) chloride.

Hailey Kang 2K

Hi!

Electronic geometry takes into account all the bonding pairs as well as lone pairs on the central atom. molecular geometry only looks at the bonding pairs.

Hailey Kang 2K

Hi! Single bonds are always sigma bonds. Double bonds have 1 sigma and 1 pi, and triple bonds have 1 sigma and 2 pi

Hailey Kang 2K

Hi! yes, lone pairs affect both electronic arrangement and molecular shape.

Hailey Kang 2K

abby hyman wrote:Does anyone know if there is any way to review the ones you missed on midterm 2?

If you email your TA or go to office hours, they can discuss the ones you missed!

Hailey Kang 2K

The scores have been posted on ccle!

Hailey Kang 2K

I heard that there is a possibility grades will be released tomorrow! Either way, he will send out an email when they are posted :)

Hailey Kang 2K

Hi!

You can use shape as a good indicator as to whether a molecule is polar or nonpolar. I would say that you still need to check whether or not the dipole moments cancel, but shape is a good check as well.

Hailey Kang 2K

Hi!

Any time there's an uneven number of electrons it's a radical, so as others have said I would assume it's an error on the textbook's part.

Hailey Kang 2K

Hi!

Electron density refers to the probability that you will find an electron in that region.

Hailey Kang 2K

Hi!

l=5 would be a valid answer. Your l value can be all the number leading up to n-1. so for example, if n=5, all your possible l values would be 0,1,2,3,4.

Hailey Kang 2K

Hi!

Definitely going to as many UA sessions has been the most helpful for me. Other than that, the textbook problems/sections are very helpful.

Hailey Kang 2K

Hi!

Simply put, electrons that are delocalized are shared between atoms. Because resonance structures are a blend of all the possible lewis structures, this means that on a diagram, you can find these electrons in any position.

Hailey Kang 2K

Hi!

The midterm will cover the last 8 bullets of outline 2 as well as all of outline 3.

Hailey Kang 2K

Hi! Basically,atoms or ions with electron clouds that readily undergo a large distortion are highly polarizable. Because of this principle, anions that are large can expect to be highly polarizable. This is because the anion is so large, that the nucleus only has weak control over its outermost elec...

Hailey Kang 2K

Hi!

I don't think it has a huge affect so I believe nitrogen will still be smaller.

Hailey Kang 2K

Hi! I was wondering this also. The textbook did mention that the arrow pointing towards the partial positive atom is a modern notation, and the arrow pointing towards the partial negative atom is older. Since the example he did in class has it pointing towards the partial negative atom, I would go w...

Hailey Kang 2K

Hi!

Hydrogen bonds occur between atoms with lone pairs, but they also can only bond with Nitrogen, Oxygen and Fluorine

Hailey Kang 2K

Hi!

The difference between the two is that a dipole-dipole attraction is the force between molecules, while the polar covalent is in between atoms.

Hailey Kang 2K

Hi! How I solved it was I drew out the Lewis structures for all of them and looked at the different bonds. For multiple bonds (double & triple bonds), they are going to be "shorter and stronger".So for example, in part a, CO has a triple bond, so it will be the strongest. I will attach...

Hailey Kang 2K

Hi!

Normally when the question is asking for the most stable structure, you are going to want to find the formal charge.

Hailey Kang 2K

Hi!

One of the things that probably helped me the most was definitely attending as many UA sessions as possible. The worksheets are super helpful, but also a lot of people will ask questions that you didn't even think up but end up being super important. Textbook problems were very helpful as well!

Hailey Kang 2K

Hi!

I would say the easiest way to remember it is # of valence electrons- # of lines & dots around that element

Hailey Kang 2K

Hi!

I would definitely recommend going to the UA sessions. They have really helpful worksheets and give very detailed and helpful explanations for everything!

Hailey Kang 2K

Hi!

Dr. Lavelle said there are subshells past f but the only ones we need to worry about for this class are s,p,d,f.

Hailey Kang 2K

Hi!

The total number of electrons is equal to the atomic number.

Hailey Kang 2K

P represent momentum! The equation to find momentum is p=(mass)(velocity).Also remember to convert to SI units!

Hailey Kang 2K

Hi!

While you're solving the problem, you should always convert to meters since it is an SI unit. Sometimes the question will ask for the wavelength in other units like nm, but that should only be converted at the very end.

Hailey Kang 2K

Hi!

The Rydberg's equation only work for for Hydrogen atoms and other single electron atoms.

Hailey Kang 2K

Hi!

If the kinetic energy is equal to 0, you would set hv equal to the work function. This is because in order to remove an electron from the surface, the energy of the photon must be at least equal to or greater to the work function.

Hailey Kang 2K

Hi!

Sapling randomized the homework questions so it's hard to tell which is which. Dr. Lavelle said we definitely need to know 19 of them, so I just picked out the 19 questions with topics that we have learned.

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