CHEMISTRY COMMUNITY

Allan Nguyen 2G

I highly recommend taking breaks or taking walks in the middle of study or work sessions. Like don't spend the breaks on your phone but do something that lets your brain take a break essentially.

Allan Nguyen 2G

I highly recommend taking breaks or taking walks in the middle of study or work sessions. Like don't spend the breaks on your phone but do something that lets your brain take a break essentially.

Allan Nguyen 2G

I feel like I lost all motivation this quarter, but I'm taking less classes next quarter so I hope everything goes well.

Allan Nguyen 2G

50 points but don't forget that extra posts from previous weeks don't count I think

Allan Nguyen 2G

I plan on dorming in the Fall if I'm able to be vaccinated by then. Remote learning or not, I'm going stir crazy from being home 24/7

Allan Nguyen 2G

Studying for the final in one day is definitely not it. You gotta split it so your don't overload yourself in one study session. I did that for the last midterm and learned my lesson :(

Allan Nguyen 2G

My favorite movie of all time is Interstellar.

Allan Nguyen 2G

I've gotten involved in Vietnamese Community Health (VCH), and I plan to get involved in more orgs and clubs once we get back on campus.

Allan Nguyen 2G

I found quantum to be really great because it was all plug and chug lol

Allan Nguyen 2G

I saw (gr) in question 6M.3 for (d) and was wondering what that means. Also, does this have any significance in cell diagrams and galvanic cells in general?

Allan Nguyen 2G

I'm going to just binge shows and play video games. Forgetting about school and relaxing is so nice in breaks like this.

Allan Nguyen 2G

Hello, can someone help with #18? I am not sure how to get started with this problem. Thanks in advance!

Allan Nguyen 2G

This probably isn't the best advice but I literally just study to the point I am no longer nervous. I kinda just do as many practice problems as I can and it just makes more confident in doing chemistry problems in regards to future exams.

Allan Nguyen 2G

I'm assuming it's going to be just like last quarter for Lavelle's 14A class where the final was cumulative and the amount of questions for each section was based off of the amount of time we spent on each unit.

Allan Nguyen 2G

Keeping a to-do list for the day really keeps you on top of everything. Ever since I starting making a to-do list for my daily tasks, it's been much easier managing time for each task for the day.

Allan Nguyen 2G

Hello, can somebody help me with this question? Thanks in advance!

Allan Nguyen 2G

I'm probably just going to watch some shows and play video games. Perfect way to destress in my opinion.

Allan Nguyen 2G

I'll be taking Chem 14C, LS 7B and Psych 10

Allan Nguyen 2G

It really just depends what you want your answer to end in. 8.314 is typically used when you want your answer to end in joules.

Allan Nguyen 2G

I found this Chemistry Community post from Lavelle in which he posted a list of thermodynamic definitions. https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=128&t=9661 Adiabatic (also called adiabatically isolated system) An adiabatically isolated system has only adiabatic boundary sectors. En...

Allan Nguyen 2G

It's the lectures from weeks 4-6

Allan Nguyen 2G

Both solve for q and m or n in the equation represents specific heat capacity or molar heat capacity.

Allan Nguyen 2G

I've been feeling nervous myself. I feel like the thermodynamics section ramped up so much in comparison to previous units. We still have a week left till the midterm though so I hope everyone is confident by then.

Allan Nguyen 2G

I remember some UA sessions where they did midterm review for the first hour and new material for the second half.

Allan Nguyen 2G

I believe it'd be N2O since it can have multiple orientations and also has resonance. Also, I found this other post on Chemistry Community to be very helpful in relation to your question. https://lavelle.chem.ucla.edu/forum/viewtopic.php?t=10290 To calculate the residual entropy, you need to know ho...

Allan Nguyen 2G

From what I've heard for this class, getting more than 200 points lets you pass the class. Basically, a 50% in this class is a passing grade.

Allan Nguyen 2G

I've been watching Neon Genesis Evangelion. It's such a classic show.

Allan Nguyen 2G

Hello, can someone help me with this problem for Sapling? Thanks in advance!

Allan Nguyen 2G

It depends on your TA but I heard from others that you can still get chem community points back if you make up for the posts that you missed for a certain week.

Allan Nguyen 2G

Hello, similar to what everyone said, when there is a negative value for work that means the work is done by the system whereas when the value for w is positive work is being done on the system by the surroundings. I found this video by the Organic Chemistry Tutor to be very helpful! https://www.you...

Allan Nguyen 2G

I know that this is a slightly different question, but I would also really appreciate any tips that you guys have for studying for the midterms or studying for this class in general. Similar to what others have said, I've found attending UA sessions, textbook and Sapling to work really well. Also, ...

Allan Nguyen 2G

Yes it is a strong acid

Allan Nguyen 2G

It's seems like the only professor for 14C is Castillo

Allan Nguyen 2G

AdilaAhmed3I wrote:They simply factored out that negative. Your set up is correct and will get the same answer

Oh I see, how did I not see that loll

Allan Nguyen 2G

Hello, this is a really minor problem but for 6E.1 in the textbook, the answer in the solutions manual puts in the c value for the quadratic equation as positive. Are you supposed to do that or am I doing something wrong? I put a screenshot of my work and the answer in the solution manual for compar...

Allan Nguyen 2G

I believe it's up to last Friday's lecture, so that would be Lecture #8 (Fri, 01/22/2021)

Allan Nguyen 2G

The smaller the pka and higher the Ka the stronger the acid and vice versa the higher the pka and smaller the Ka the weaker the acid.

Allan Nguyen 2G

Anything solid or liquid is never included in an ice table.

Allan Nguyen 2G

I was able to use a graphing calculator last quarter for Lavelle's Chem 14A class so it should be okay.

Allan Nguyen 2G

Textbook problems and UA sessions are your go to for studying in this class. Exposing yourself to different problems just helps you in the long run with exams.

Allan Nguyen 2G

They're essentially the same thing

Allan Nguyen 2G

For chemistry problems, I'm pretty sure you'd always use kelvin.

Allan Nguyen 2G

So we have just the 50 minute lecture time for the exam? And about how long did you have for each question? Like were there a lot of shorter questions or was it just a few questions that took a while? For me, I ended the midterms with a lot of time since a decent amount of questions were conceptual...

Allan Nguyen 2G

For last quarter, he only had it for the fundamentals and quantum. I'm assuming it'll be the same and there will be no addition of the audio visual focus topics.

Allan Nguyen 2G

I know that they're both different, but how can I differentiate between the two in terms of application and concepts?

Allan Nguyen 2G

They're the same and the terms are used when you look at the K value to determine whether reactants or products are favored in a reaction.

Allan Nguyen 2G

Hello, I've been having trouble trying to work this problem. I don't know if I'm doing it right but I multiplied the given equilibrium moles of O2 by 2 to get 0.240 mol for SO2. I then added the equilibrium moles of SO2 and O2 to get 0.360, which I then subtracted from the 0.820 initial moles of SO3...

Allan Nguyen 2G

You can calculate Q to figure out where the reaction will proceed if given the equilibrium constant, K. Similar to what Silvi said, when Q<K the reaction will proceed to the right and vice versa when Q>K the reaction will proceed to the left.

Allan Nguyen 2G

I think it's just for equilibrium, since for 14A the audio-visual topics were only for the fundamentals review and early quantum.

Allan Nguyen 2G

They're optional but I found them to be helpful for Chem 14A last quarter in terms of review and getting used to Sapling.

Allan Nguyen 2G

Like everyone else has replied to on this post, I highly recommend the UA workshops because they expose you do different types of problems that are very similar to questions on midterms and final exams.

Allan Nguyen 2G

Going off of what Samantha said, it really depends on the context of the problem whether the compound is being used as an acid or base. Molecules that can act as both as an acid or base is considered amphiprotic. For example, HCO3- can become CO3^2- or H2CO3. Edit: Sorry I didn't mean to say amphote...

Allan Nguyen 2G

While I can't really explain why linear molecules can have lone pairs, I know for a fact that linear molecules can have three or four lone pairs. I put an attachment for the VSEPR geometries and in the bottom right there are two linear VSEPR geometries with three or four lone pairs. I think it's bec...

Allan Nguyen 2G

For hydrogen bonding, we know that a hydrogen bond can only occur between an H atom and a F, O, or N atom. When looking at thymine, we need to look at the amount of hydrogen atoms and the amount of lone pairs in any atom that is F, O, or N. In the thymine molecule, there's two hydrogen atoms, so tha...

Allan Nguyen 2G

I think you should memorize all of them but I remember one of the UAs saying that there are some shapes such as T-shape being pretty rare to occur in problems. The ones I put an emphasis on were bent, linear, tetrahedral, trigonal planar, and trigonal pyramidal but yeah I'd still try and memorize al...

Allan Nguyen 2G

Yes I think I saw in another chemistry community post that when H2O is within the coordination compound, it's name is aqua. For example, in the coordination compound [CrCl3(NH3)2(OH2)]+ , H2O would be referred to as aqua. When outside of the bracket, H2O is referred to as hydrate. Honestly, I'm not ...

Allan Nguyen 2G

Hello, I'm having trouble classifying whether a salt is acidic, basic, or neutral. Can someone explain to me how to determine what these salts are? Thanks in advance!

Allan Nguyen 2G

Don't forget that a molecule can have polar bonds but can still be a nonpolar molecule due to its shape.

Allan Nguyen 2G

Super anxious but studying and doing more practice problems makes me feel more ready for the upcoming final :)

Allan Nguyen 2G

There's a list of ligands on Dr. Lavelle's Chem 14A site titled "Naming Coordination Compounds." I'm just going to assume he wants us to memorize those since they're on his site.

Allan Nguyen 2G

Adding onto what the post above said, an example of this could be the strong acid HCl and the weak acid HF. We can tell that HCl is a strong acid because it's bond between H and Cl is weak. Since the Cl atom has a larger atomic radius this creates a longer bond length resulting in a weak bond. The w...

Allan Nguyen 2G

There is a pdf on Lavelle's Chem 14A website titled "Naming Coordination Compounds." I was told that these are the main ones that Lavelle wants us to memorize.

Allan Nguyen 2G

A photon checks into a hotel and the bellboy asks, "Can I take your bags?" The photon answers, "No thanks, I'm travelling light."

Allan Nguyen 2G

I think it is too because I can't see any way you'd get sp3 for the hybridization of ethylene, only sp2.

Allan Nguyen 2G

That's really odd, I have the same exact lewis structure as you and it says that it's correct. Did you get sp^3 for the hybridization of the carbon and oxygen atoms and say that it was polar?

Allan Nguyen 2G

Hello, I just wanted to link this here since I found this simulation to be very helpful for me when visualizing VSEPR shapes. Just wanted to link this out there to anyone else having trouble visualizing VSEPR shapes.
https://phet.colorado.edu/sims/html/mol ... es_en.html

Allan Nguyen 2G

I believe the De broglie equation is used when determining whether the object being evaluated has wavelike properties or not. For example, if you're given the energy of an object that is not light, you can use the E=hv equation to find the velocity and use that velocity to plug into the De broglie e...

Allan Nguyen 2G

I was just wondering, will there still be UA sessions for this week?

Allan Nguyen 2G

The textbooks questions and readings have helped me a lot in understanding how to do calculation based problems along with conceptual based problems. Also, the workshops that happen every week are so helpful, they expose you to different types of questions and have help me a lot on the midterms.

Allan Nguyen 2G

I remember there was like a scale to determine covalent or ionic character where if the electronegativity difference is greater than 1.5 its more ionic and if less an 1.5 its more covalent.

Allan Nguyen 2G

When we look at the periodic table, we know that 5s and 5p subshells are of a higher energy level than 4d. The electron configuration for Sb is [Kr]4d^10 5s^2 5p^3. We know that valence electrons are the outermost electrons of an atom, so when we look at this electron configuration, the 5 electrons ...

Allan Nguyen 2G

Hello, I was going over the worksheet from Riya Shah's workshop today and one of the questions asks to put Br2, Cl2, and I2 from lowest to highest BP. Since these molecules only have LDFs, the molecule with more electrons and larger molar mass form stronger LDFs in which the answer was Cl2<Br2<I2. H...

Allan Nguyen 2G

Hello, I was wondering how do you figure out which resonance structure makes the most dominant contribution to a resonance hybrid? Thanks in advance!

Allan Nguyen 2G

We use the same sheets we used on the last midterm which was the equations and constants sheet along with a periodic table.

Allan Nguyen 2G

I believe induced dipole-induced dipole bonds occurs among all atoms and molecules. This occurs when the molecule temporarily distorts another neighboring molecule causing a temporary attraction causing the induced dipole-induced dipole bond. Dipole-dipole interactions can only occur between two pol...

Allan Nguyen 2G

Dipole dipole and LDFs are both intermolecular forces. LDFs occur between every atom and molecule in intermolecular forces, while dipole dipole only occurs between polar molecules that are dipole.

Allan Nguyen 2G

I find taking deep breathes really helps. Also, whenever I find myself taking too much time on a problem I just move on the next problem and go back to it later. What helped me the most is just doing practice problems, so when it came to the test I knew what to do immediately.

Allan Nguyen 2G

The quarter system has been going pretty fast but I've been managing my time pretty well and am able to keep up. I'm beginning to feel burnt out with all these midterms and work going around but we're already halfway there.

Allan Nguyen 2G

I remember Lavelle saying that in nature wants to be stable. By looking at the overall formal charge of a molecule, the Lewis structure that would contribute the most I assume would be the most stable molecule.

Allan Nguyen 2G

Hello, can someone help me with this? I know that double bonds are shorter in pm than single bonds, but I'm fully understanding the problem as I keep getting it wrong. Thanks in advance!

Allan Nguyen 2G

I believe the p^n format is less descriptive than the px, py, pz format. The latter format is more specific and helps display Hund's rule in which each orbital in the 2p subshell is occupied with one electron before any orbital has two electrons.

Allan Nguyen 2G

I remember hearing that ionization energy increases across a period. Why does oxygen have a lower ionization energy than nitrogen?

Allan Nguyen 2G

They both increase across a period and decrease down a group.

Allan Nguyen 2G

For the second part of this problem, you want to use the de Broglie equation and rearrange it to find the velocity of the electron. So after rearranging the equation it should be v = h/m λ. Convert the wavelength to meters, and plug in the values and you should get 290.96 m.s^-1 for velocity. I woul...

Allan Nguyen 2G

With the wavelength, you can look at the electromagnetic spectrum and compare your wavelength to the wavelengths that are on the spectrum. Here is an attachment, you can see that the visible light portion is around 380 nm to ~700 nm. I just memorized the general parts of the electromagnetic spectrum...

Allan Nguyen 2G

For the second part of this problem, you want to use the de Broglie equation and rearrange it to find the velocity of the electron. So after rearranging the equation it should be v = h/m λ. Convert the wavelength to meters, and plug in the values and you should get 382.84 m.s^-1. I would then use th...

Allan Nguyen 2G

When the problem asks to find the energy to remove an electron, that would be considered the work function or threshold energy. If a problem asks for the energy that causes the photoejection of an electron, that would be the incoming light or incident light.

Allan Nguyen 2G

I think when Dr. Lavelle said up to 1D.2, he just meant the section to read up to for the 1D section. I don't think there are any problems you need to do because on the outline, he did not assign the problem 1D.2. I think he is just going to test us on concepts.

Allan Nguyen 2G

Hello, I was wondering if someone could help me with this. I was late to Kate Santoso's workshop last night. Thanks in advance! Q1A. The uncertainty in the momentum of a football thrown by Tom Brady during the superbowl traveling at 40 m/s is 1 x 10-6 of its momentum. What is its uncertainty in posi...

Allan Nguyen 2G

I would just make sure to check for unit conversions. Don't forget that the joule unit in Planck's constant for the De Broglie equation is 1 kg.m^2.s^-2 Does this mean that you do not input the value as 6.626*10^-34 J.s into the equation? My bad, I didn't mean to put the 1 before the kg.m^2.s^-2. Y...

Allan Nguyen 2G

I believe that in the middle of calculations, you wouldn't round down values to sig figs. However, when calculating your final answer, you would then use sig figs because if you used sig figs in the middle of the problem and then used those values to calculate the solution, the answer would be less ...

Allan Nguyen 2G

I would just make sure to check for unit conversions. Don't forget that the joule unit in Planck's constant for the De Broglie equation is 1 kg.m^2.s^-2

Allan Nguyen 2G

I suggest just redoing practice problems from the textbook and post-assessment modules. Also, the workshops are also really helpful if you want extra practice.

Allan Nguyen 2G

I'm having trouble figuring out to get started with this problem. Thanks in advance! "A blue line is observed at 486.1 nm in the spectrum of atomic hydrogen. Determine the values of n for the beginning and ending energy levels of the electron during the emission of energy that leads to this spe...

Allan Nguyen 2G

I've just been taking notes from the lectures, and doing the textbook problems assigned for each unit. Something that really helps is attending the workshops, the UAs explain everything so well and the worksheets help out so much.

Allan Nguyen 2G

Dr. Lavelle changed the negative sign in -4.09x10^-19 J to positive sign because I think he specifically stated that energy cannot be negative. The negative sign represented that the electrons energy decrease and was released as electromagnetic radiation. If you plug the -4.09x10^-19 and divide it b...

Allan Nguyen 2G

An excited hydrogen atom emits light with a frequency of 1.14 x 1014 Hz to reach the energy level n = 4. In what principle quantum level did the electron begin? Does anyone know how to do this with the E = -hR/n^2 equation or does it have to be the Rydberg equation? I just remember Dr. Lavelle sayin...

Allan Nguyen 2G

Yes, it's due midnight Sunday Week 3 (Oct. 25) since we will still be learning Quantum next week

Allan Nguyen 2G

For Part A you use KE = 1/2 mv^2. The mass of an electron is approx 9.109*10^-31 kg. Therefore, by plugging in what's given into the formula, you should have (1/2)*(9.109*10^-31)(6.61*10^5)^2 which should result in the answer.

Allan Nguyen 2G

Hello, can someone explain this problem to me? I am having trouble understanding the problem. I thought that mols of solute don't change in a dilution. G.25 Practitioners of the branch of alternative medicine known as homeopathy claim that very dilute solutions of substances can have an effect. Is t...

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