CHEMISTRY COMMUNITY

Valerie Tran 2B

Kaleb Tuliau 3E wrote:Are the chemistry community points additive or is there no way to regain those lost points??

They're additive, as long as you have 50 posts by the end of the quarter, you should get full credit.

Valerie Tran 2B

The graph is plotting 1/concentration vs time and as time increases, the concentration of a reactant will decrease. Since the y axis is 1/concentration, the y value will increase as time goes on because concentration is in the denominator

Valerie Tran 2B

A compound is an intermediate if it is produced in one step of the reaction and is consumed as a reactant in a later step, but does not appear in the overall reaction. Remember, this is different from a catalyst.

Valerie Tran 2B

In a galvanic cell, the electrons move from anode to cathode. The cathode becomes negatively charged which means electrons would stop moving towards the cathode because like charges repel. In the salt bridge, negatively charged ions move from the cathode solution to the anode solution, which removes...

Valerie Tran 2B

https://socratic.org/questions/how-do-y ... a-compound

This is a really good website with examples as well. Hope this is helpful to you!

Valerie Tran 2B

Kristine_Aramyan_3K wrote:what's your fave food/snack/dessert? i'm personally craving banana bread rn

This isn't food but I have boba like 4 times/week. I love ramen as well and sweet foods (ice cream, cookies, etc) at night when I'm studying.

Valerie Tran 2B

Please don't think about what could be because it has already passed. Try not to be regretful and focus on the accomplishments. There's nothing left to do but relax until you get results so keep yourself away from schoolwork and do some fun things. Music also helps to block out anxious thoughts.

Valerie Tran 2B

It will usually give you that info (I think the textbook does this). But you can determine which reaction is fast or slow if you are given the rate law. The reactants present in the rate law are the reactants in the slow reaction.

Valerie Tran 2B

In an isothermal reaction, delta U will be 0. You can also calculate q and w since delta U = q+w

Valerie Tran 2B

It can be included if it is present in the reaction mechanism but we usually leave it out because its concentration doesn't affect the rate.

Valerie Tran 2B

For this class, we can consider it independent because it varies so little but technically it will increase with temperature.

Valerie Tran 2B

These are both great posts, I was never able to make clear steps for acidic and basic redox reactions so I appreciate these. Thanks, guys!

Valerie Tran 2B

Yes, chemistry community is open to the public, so while you won't be able to post anymore, you can always look for questions or view old posts.

Valerie Tran 2B

I'm pre-med and the coursework looks grueling but it's only been 2 quarters so I'm gonna keep going. My major aligns with pre-med reqs so it's easy to decide not to go to pre-med if I decide I want to stop after 4 years. I really want to meet other pre-meds and join clubs and stuff once we can go on...

Valerie Tran 2B

Kinetic stability basically occurs when the reactants react really slowly. The slower the reaction occurs, the greater the kinetic stability.

Thermodynamic stability depends on whether or not the reaction is spontaneous. This depends on the change in free energy (ΔG).

Valerie Tran 2B

Stop studying now, your brain needs a break and at this point, you know everything that you could know. Do things that make you happy and focus on the fact that you came this far and you'll be fine. Just try to keep yourself relaxed and distracted. I listen to music constantly because it helps my br...

Valerie Tran 2B

Yes, adding on to the previous comments, this is a simple example of a pseudo-rate. Rate = k[A][B]. k is a second-order rate constant. If there is excess of [B] compared to [A], then [B] will not change significantly during the reaction so it can be considered a constant. [B] can be absorbed into th...

Valerie Tran 2B

I saw this on a different chem community post but my understanding is "standard conditions" uses 298K (gases, liquids, and solids). 273K is for STP which is a subset of standard conditions and specifically refers to ideal gases.

Valerie Tran 2B

I was also wondering this but when I looked it up, it seems like a concentration cell is a type of galvanic cell so I'm confused. I know that concentration cells are made of two half-cells, each containing the same electrodes, but different concentrations. The whole point is to establish equilibrium...

Valerie Tran 2B

Jeffrey Hablewitz 2I wrote:What does this formula represent/what is it used for?
P_n ∝ e(-E_n/k_bT)

Have we used this before in class, I saw it on the formula sheet but I can't recall it.

Valerie Tran 2B

Both, a catalyst will lower the activation energy of the reverse reaction, therefore, speeding up the rate of the reverse reaction.

Valerie Tran 2B

It was also in some Sapling problems for week 9/10 I think. It's good to know although I'm not sure how much of it will be on the final. I'd familiarize myself with the basic uses of it just in case.

Valerie Tran 2B

Catalysts are present as reactants in the very beginning and are used up during the reaction but are regenerated at the end. Intermediates are not present in the initial reaction but are produced within one of the steps and then consumed within another step (they are used up completely) ex: Step 1: ...

Valerie Tran 2B

According to the Arrhenius equation, increasing the temperature would increase the rate constant

Valerie Tran 2B

I was also confused about this question and I found an old chem community post that was pretty helpful

viewtopic.php?t=3585

Valerie Tran 2B

It's possible somewhat. You won't be able to fully understand concepts or get adequate practice trust me on that. However, you can get try a general understanding of the concepts and just focus on ones that you feel are most confusing. I definitely wouldn't recommend this so try allocating a little ...

Valerie Tran 2B

These tips have helped me a lot especially since I'm someone who just works without stopping until everything is done which has been really bad for my mental health, so thanks to everyone for some great tips.

Valerie Tran 2B

I like redox reactions and gas laws. These are topics I've enjoyed since high school even if I'm not that good at them sometimes.

Valerie Tran 2B

When you melt sugar and water into invert sugar syrup, it is a hydrolysis reaction that can be sped up with catalysts such as cream of tartar or lemon juice. I never thought about it but I do make a lot of syrup so it's interesting to see the chemistry in action and I have this thread to thank for t...

Valerie Tran 2B

For some reason, I always find myself stress-baking during finals week--just to get my mind off things. I can relate to this one. I'm stress-making boba and drinking way too much tea. It's scary and yet so tasty. My weighing scale going up up up. Boba has to be my ultimate weakness, I could save a ...

Valerie Tran 2B

Sunday, March 14th at midnight

Valerie Tran 2B

Technically yes, but very little so you can consider it constant across small temperature ranges

Valerie Tran 2B

To identify the slow step and the reaction mechanisms, you need to consider: 1) the sum of elementary steps = overall reaction 2) the mechanisms must agree with the experimentally determined rate law. Whichever elementary step has a rate law that matches the overall reaction's rate law is the slow s...

Valerie Tran 2B

For this problem, you would the rate as (Concentration of A for 222 sec - Concentration of A for 0 sec)/(222-0) then multiply it by -2

For example:
if 0 sec = 0.790 M
222 sec = 0.140 M
then (0.140 - 0.790)/(220-0) and mulptily that by -2

Valerie Tran 2B

For chem 30A, it says we need chem 20B as a pre-req, does that mean 14B will work as well since the 20 and 14 series are interchangeable this year?

Valerie Tran 2B

It represents the frequency of collisions between reactant molecules at standard concentration (which is why it's also called frequency factor). It is temperature-dependent and should be given to you unless you're needing to find it, in which case you would use the Arrhenius equation and plugin valu...

Valerie Tran 2B

This hits pretty close to home for me. Being completely online has led to such a big decrease in my motivation that it's making it harder for me to envision so many more years of school especially when the topics I loved to learn are becoming harder to care about. I try not to look too far into the ...

Valerie Tran 2B

I've literally never been to campus so all I have to look forward to are what I've heard online. I just want to be able to study in the library or outdoors and I want to be able to sit in lecture halls and do labs in person. I haven't even thought about the social aspect yet but I know there are gre...

Valerie Tran 2B

Yeah, my TA said that as long as you have 50 posts by the end of the quarter, you'll get full points even if you didn't space them out weekly.

Valerie Tran 2B

Handwriting is my go-to, I am simply not tech-savvy enough to do e-notes even though the ones people take on iPad look really nice. My notes just consist of the foundations and outlines of concepts since I keep practice problems in a separate notebook. I go to my notes for reviewing concepts and equ...

Valerie Tran 2B

Yes, a catalyst works to lower the activation energy, which applies to both the forward and reverse reactions (the rate will increase both ways).

Valerie Tran 2B

You do not include intermediates in the rate laws(because they are produced and then used up by the reaction). The rate law should only include reactants. For example: Step 1: A + B → C Step 2: C → D Overall: A + B → D (C is the intermediate and does not appear in the overall reaction) rate law = k[...

Valerie Tran 2B

I forgot, we have until Sunday at midnight to finish our chem community posts right? But I do remember my TA saying chem community would be closed before the final so I was wondering when is the deadline for posts?

Valerie Tran 2B

First, you need to assign oxidation numbers. If an atom's oxidation number decreases in a reaction, it is reduced. If an atom's oxidation number increases, it is oxidized

Valerie Tran 2B

I am also confused, wouldn't the method used depend on what's given? Why would any one method be more accurate?

Valerie Tran 2B

I think that K is the rate constant when you take into account the forward and reverse reactions (multiple reactants) but k only takes into account the forward reaction when you only have one reactant. I'm not sure though.

Valerie Tran 2B

What chemistry classes are you guys taking next quarter? Are you moving to the 20-series or starting O-Chem or anything else? Let me know!

Valerie Tran 2B

I'm not pre-med but I am still planning on applying for a STEM graduate degree. However, this quarter has specifically been tough and it looks like I'll barely pass the class with a C. I'm a freshman and am wondering if it's best to retake this class or continue on to 14C and get a better grade in ...

Valerie Tran 2B

It's nice to see that I'm not the only one feeling burnt out and it makes the imposter syndrome easier to deal with since hustle culture is so real. I'm hoping that the break before the spring quarter will help me but I'm really just trying to push to the end. Motivation is super low but it would be...

Valerie Tran 2B

So I am offically the dumbest person alive and did not do any of my chemistry community questions this whole quarter because I completely forgot, I thought it was just a last quarter thing but um no so what happens when you retake a class and how do you sign up for it, please help Well you could al...

Valerie Tran 2B

Does anyone know how to calm down your anxieties before you take this final? Since having test anxiety can be very distracting while you're trying to study or even while you're taking the test itself. Open to any tips:) Does anyone just zone out during the exam or get stuck in a brain fog and just ...

Valerie Tran 2B

That's the goal or just get to LA even. I might look for an apartment but I'd love to dorm if possible. I would hate to have to do labs online and stuff like that

Valerie Tran 2B

1. Balance the reaction
2. Convert into moles.
3. Use stoichiometry for each individual reactant to find the mass of the product produced.
The reactant that produces a lesser amount of product is the limiting reagent.

Valerie Tran 2B

An oxyacid is an acid that contains an oxygen atom bonded to a hydrogen atom and at least one other element. The general structure is X-O-H.

Valerie Tran 2B

Oh I saw this too, it's a great cheat sheet and it's really clear on how to get to each part

Valerie Tran 2B

I think the difference between tetrahedral and square planar is related to their hybridization configurations. Additionally, I think that a square planar configuration is in one plane whereas tetrahedral is in multiple planes. The square planar also has 2 lone pair vs tetrahedral has no lone pairs

Valerie Tran 2B

I really need to start going to more office hours with TAs and UAs. I don't think I utilized that resource as much as I could.

Valerie Tran 2B

Just reviewing topics I struggled on before 14b as well as making sure I read through my notes often.

Valerie Tran 2B

Salt is produced by the reaction of an acid with a base. A salt consists of the positive ion (cation) of a base and the negative ion (anion) of an acid

Valerie Tran 2B

Building on the last reply, you can look at the hydrogens in each compound before and after the reaction. If the number of hydrogens has decreased that substance is the acid (donates hydrogen ions). If the number of hydrogens has increased that substance is the base (accepts hydrogen ions)

Valerie Tran 2B

Everything should be in by Saturday

Valerie Tran 2B

I did finish but I also felt rushed on the last couple of questions so I'm not confident in my answers either.

Valerie Tran 2B

Yeprem wrote:Are the basic ones basic because they don't even have an H in them?

I don't

No basic solutions can also have H+ ions. They are basic because the concentration of hydroxide (OH−) is more than the H+ ions.

Valerie Tran 2B

Thank you, Dr. Lavelle, for all the work you put in to ensure we had the resources necessary to succeed in this class. I can't tell you how much I appreciated all the review sessions and office hours that were available. Honestly, this was a very enjoyable class and I look forward to it next quarter

Valerie Tran 2B

Since we are done with this quarter, I wanted to know: What are some good study methods/tips you've found for online learning (especially for chemistry since we'll all have it next quarter)? What are you gonna do in terms of organization for next quarter?

Valerie Tran 2B

I watch study with me videos. They usually have nice bg music and it makes me more productive to see someone else studying.

Valerie Tran 2B

This is due to an electron being added to an already half full orbital in oxygen, which results in electron-electron repulsion, which will lower the ionization energy. The 2p sublevel for N has one electron in each orbital. O has two electrons in the first orbital and one in each of the other two or...

Valerie Tran 2B

Samin Kabir wrote:Why does acid rain exist. Is it because of air pollution, and what can be down about it?

Since acid rain is caused by fossil fuels, we could reduce our carbon footprint by using renewable energy resources, such a solar, hydroelectric, and wind power.

Valerie Tran 2B

705512695 3K wrote:Also are we supposed to use the same zoom link that we used for our midterms for final or is there another way the final is going to be proctored?

The links are in the FINAL tab on ccle

Valerie Tran 2B

Yeah not sleeping is pretty much my routine. I don't last minute cram anymore because like if I don't know it know I probably wont overnight. I just watch fun videos to keep my mind off stress even if I cant sleep.

Valerie Tran 2B

How soon do you think our grades will be up after the final? Also do we have until Sun at 11:59 to finish our last chem community posts?

Valerie Tran 2B

Jillian's answer is very good! By drawing out the structure, you can visualize the problem easier.

Valerie Tran 2B

The definition of amphoteric is a species that is able to act as both a base and acid, which means it should be able to accept and donate a proton when need be.
Ex: H2O can become H3O+ or OH- so it is amphoteric

Valerie Tran 2B

Yes, see-saw comes from trigonal bipyramidal but with a lone pair. So when a lone pair is added, we want to place it as far away as possible from the bonding pairs due to electron-electron repulsion. When we place it in the "trigonal" part of the shape, there is an approximately 120 degree...

Valerie Tran 2B

Trying to get some peace before next quarter haha! Just catching up on sleep and youtube, maybe social distance present drop offs for friends. Not much to do with quarantine.

Valerie Tran 2B

A monodentate ligand has only one donor atom used to bond to the central metal atom or ion. Some examples of monodentate ligands are chloride ions hydroxide ions and ammonia Bidentate ligands have two donor atoms which allow them to bond to a central metal atom or ion at two points. An example of a ...

Valerie Tran 2B

I think so. If you can do those problems confidently then you should be fine for anything on the final.

Valerie Tran 2B

11:30am – 1pm, Sunday December 13

It's on the chem 14a website under final review sessions and final exam.

Valerie Tran 2B

A buffer is an aqueous solution containing a weak acid and its conjugate base or a weak base and its conjugate acid. A buffer's pH changes very little when a small amount of strong acid or base is added to it. It is used to prevent any change in the pH of a solution so you would use it in an experim...

Valerie Tran 2B

So I'm doing my last minute studying and I was wondering, how do you guys break down a topic that you have trouble with? Do you do lots of practice or watch videos or something else? Let me know

Valerie Tran 2B

Don't work for more than an hour without a break, you'll get less productive and the quality of your work will lower. I used to be able to just crank out my homework in like a 3-4 hour period but I've found I'm more productive if I give myself breaks every hour or so. Set a schedule and try to stick...

Valerie Tran 2B

Yes, a higher boiling/melting point indicates strong bonds that need a lot of energy to break so the higher a boiling/melting point is, the stronger the INFs are.

Valerie Tran 2B

Yeah, I think it won't be necessary to memorize the specific values(besides maybe visible light), rather you should be able to list them in the proper order and know which wavelengths are longer or shorter. It's also good to associate examples with each type of radiation to help with placing them in...

Valerie Tran 2B

Is the final going to be with our TAs or will it be a whole class thing because I think he said there will be a separate link to it in the FINAL folder so I just wanted some clarification?

Valerie Tran 2B

Lone pairs do affect the shape of a molecule so technically for a molecule to be 180 degrees, it can't have lone pairs(ex: BeCl2). But, a molecule can also have lone pairs and still be 180 degrees(ex: XeF2). The electron geometry of this molecule is trigonal bipyramidal since xenon has two atoms att...

Valerie Tran 2B

As2O3 is amphoteric because As is a metalloid and can act as either an acid or base. I'm not sure why he put it as an acidic oxide but I think you should classify it as amphoteric.

Valerie Tran 2B

To figure out the number of unpaired electrons predicted for the ground-state configuration of an atom, just find electron configuration and use Hund's rule to determine how many orbitals in the subshells have only one electron. So for Ni 2+, the electron config: [Ar]3d^8. Since the d subshell has 5...

Valerie Tran 2B

Thanks for the video, it was very helpful

Valerie Tran 2B

Yes, you are correct. Lewis acids and bases are defined in terms of being able to accept/donate electron pairs but Bronsted Lowry acids and bases are defined in terms of being able to accept/donate hydrogen ions ( H+ )

Valerie Tran 2B

He says on his website that the final is the same format as the midterms so its probably safe to assume there are only multiple choice

Valerie Tran 2B

Make sure you're as prepared as possible and not just with the material but also your workspace. Especially with online testing, making sure you have a good connection, a quiet place, all your materials, etc. Knowing that you're prepared can help ease a lot of anxiety. Don't try to last-minute cram ...

Valerie Tran 2B

Ionization energy is the energy required to remove an electron away from an atom

Electron affinity is the energy released when an electron is added to the atom

Valerie Tran 2B

First, you need to determine E using E = hc/wavelength (use 1064x10^-9) for wavelength. You would get 1.867x10^-19. Then you use the conversion for Joules to eV by dividing E by 1.602x10^-19 to get 1.165eV. Electron affinity is the difference between the incident radiation from the laser and the mea...

Valerie Tran 2B

First, you need to determine E using E = hc/wavelength (use 1064x10^-9) for wavelength. You would get 1.867x10^-19. Then you use the conversion for Joules to eV by dividing E by 1.602x10^-19 to get 1.165eV. Electron affinity is the difference between the incident radiation from the laser and the mea...

Valerie Tran 2B

For me, I know that electronegativity increases going up and to the right. From there you can start to derive other trends since periodic trends(effective nuclear charge, affinity, ionization energy, etc) are related. I'd recommend knowing the relationships between these/the fundamentals behind them...

Valerie Tran 2B

In order of greatest strength to least strength, it goes: ionic, covalent, hydrogen The reason ionic bonds tend to be stronger than covalent bonds is due to the coulombic attraction between ions of opposite charges. An electron is "taken" from one atom by another atom. In covalent bonds, a...

Valerie Tran 2B

Is Professor Lavelle still gonna have office hours this week before the midterm? Also, can you only go to your TA's office hours or can you go to others? And for the camera pointed at our station does it have to be raised so they can see the work on the paper or just level with the desk so they can ...

Valerie Tran 2B

he sent us two sheets(via email) which im sure you can find on his website to print out that we can use plus a calculator but that's it

Valerie Tran 2B

He sent us two worksheets(via email) to print out but besides those, I don't think anything else is allowed.

Valerie Tran 2B

Yeah, I think we just have zoom open on a separate device and point it at our workspace. Also, Respondus uses your camera to record your face right? so there's no need to have a separate camera at your face. I'm not 100% sure about this though

Search found 105 matches