CHEMISTRY COMMUNITY

Karen Elrayes 1L

You could also think of it as it would take more energy to break it's bonds in terms of heat capacity like changing it's state. The more complex it is the more heat is required to change its state.

Karen Elrayes 1L

I don't think there's a need to memorize. Just know that group one elements are always +1 and Oxygen is -2 and you should be able to figure it out

Karen Elrayes 1L

I took 14Bl this quarter with 14B. I'm taking 14C next quarter :)

Karen Elrayes 1L

I think a lot of us feel pretty burnt out as well and at this point are just trying to get through finals. There's so much going on and I've found talking to other people and finding that they feel the same has helped me feel less alone and less panicked.

Karen Elrayes 1L

I think a lot of us feel pretty burnt out as well and at this point are just trying to get through finals. There's so much going on and I've found talking to other people and finding that they feel the same has helped me feel less alone and less panicked.

Karen Elrayes 1L

Catalysts decrease the activation energy and so if you look at the nerst equation if the activation energy decreases then rate (k) increases. But it shouldn't affect the equilibrium

Karen Elrayes 1L

Also activation energy is really just the energy required for the reaction to actually occur and it can be manipulated so that it is faster or slower (such as use of catalysts/ enzymes) meanwhile enthalpy of a reaction is not related to its speed or reaction time.

Karen Elrayes 1L

What are all the equations that we are responsible for in electrochemistry? That section I feel like we breezed through just because it overlapped with midterm 2.

Karen Elrayes 1L

I'm not too sure to be honest, but we wouldn't need to worry about it for the exam because we will be given the correct E* values to use. Maybe someone else has a better response though :/

Karen Elrayes 1L

If the product is not removed or is in a different phase then due to equilibrium the reaction could shift from products to reactant but we only want to look at the forward reaction which is why we need to remove the product so the reaction does not shift to products forming reactants.

Karen Elrayes 1L

Why is E* always = 0V in concentration cells?

Karen Elrayes 1L

Why do we assume E* is 0?

Karen Elrayes 1L

I thought I did better than what my grade turned out to be. Probably need to focus on more concepts when studying for the final.

Karen Elrayes 1L

I honestly have been wondering about how to best approach studying for the final. I think reviewing the concepts and redoing the problems in sapling because they have explanations would be helpful. And doing the outlines afterwards would solidify any hardships

Karen Elrayes 1L

As everyone said, Lavelle doesn't usually want us to memorize things, so most oxidation stuff we'll be able to figure out.

Karen Elrayes 1L

When do we use OH- vs H2O ?

Karen Elrayes 1L

Im taking 14C and stats 13
Does anyone have any recommended courses for writing 2 course?

Karen Elrayes 1L

What are all version of enthalpy (delta H) equations we need to know at the different conditions? constant P, constant V, etc...

Karen Elrayes 1L

What is the difference between delta G and delta G knot

Karen Elrayes 1L

Thank you all, that's very helpful

Karen Elrayes 1L

I'm really confused regarding the concepts behind reversible and irreversible expansions. Will we always view them as a piston problem (which is how professor Lavelle discusses them)? And what is reversible vs irreversible?

Karen Elrayes 1L

I think it will include everything up until Friday of week 6, but professor Lavelle usually sends out an email the week before explaining exactly which material we are responsible for.

Karen Elrayes 1L

Endothermic means energy went into the system which means delta H increased so it has to be positive. And the opposite is also true.

Karen Elrayes 1L

Energy can be exchanged but matter can not

Karen Elrayes 1L

Does anyone know how many posts we are supposed to have? I lost track during the craziness of the midterm

Karen Elrayes 1L

It's a measure of chaos of a system or of the surrounding. We usually look at it as entropy increased in the system vs the surroundings

Karen Elrayes 1L

At 0 Kelvin it is thought that there was no energy at all or "absolute zero" but residual entropy still occurs because of the different forms the atoms can arrange themselves in a molecule.

Karen Elrayes 1L

As everyone said, I would look at the units you are given and the units you are trying to reach and choose the one the fits where you can cancel out the units u don't want in the final answer

Karen Elrayes 1L

I feel like this section is a lot more challenging because it's a little difficult to know how to start every problem. Any tips?

Karen Elrayes 1L

If prof. Lavelle mentions them in lecture then they are fair game

Karen Elrayes 1L

How does a calorimeter work?

Karen Elrayes 1L

It's usually when k is less than 10^-3 but you have to check the percent ionization by diving x by the initial concentration and see if it is less than 5%. Usually when k is super small, it is very likely you can approximate.

Karen Elrayes 1L

Enthalpy is the change in heat of a system at constant pressure. So we can use Final - Initial which is a state function. Heat is energy transferred due to a temperature system so it depends on the path not just Final - initial so it's not a state property. Hope this helps, I was also confused by th...

Karen Elrayes 1L

How do we do this problem?

A careless laboratory technician wants to prepare 200.0 mL of a 0.025 M HCl(aq) solution but uses a volumetric flask of volume 250.0 mL by mistake. (a) What would the pH of the desired solution have been? (b) What will be the actual pH of the solution as prepared?

Karen Elrayes 1L

6CO2(g) + 6H2O(l) → C6H12O6(aq) + 6O2 (g)
What is the effect of adding more water? I know that liquid should not affect the equilibrium composition but since glucose is aqueous wouldn't it's concentration decrease because it will become more diluted?

Karen Elrayes 1L

When calculating the K value and when setting up an ice table, what should our units be if we're calculating partial pressure.

Karen Elrayes 1L

One of the UA's said that Lavelle stated that we didn't need to worry about solving anything past a quadratic for the midterm :)

Karen Elrayes 1L

I try to go to at least 3 or 4 UA sessions per week, and then sapling and textbook homework... So 10 -12 hours I would say? I also have other classes and I'm working so i understand the struggle. Going to UA sessions as study time, is very efficient and helpful cause they reinforce stuff we are supp...

Karen Elrayes 1L

Yes that's correct, there is also a really helpful diagram in one of the lectures or textbooks!

Karen Elrayes 1L

I recommend trying to finish all the textbook problems a few days before the exam so you can attend UA sessions and ask questions and figure out what you don't know yet.

Karen Elrayes 1L

You can also try graphing the equation, and calculating where the x-intercepts are if you have a graphing calculator.

Karen Elrayes 1L

Q calculates the ratio of products to reactants at anyone point not just equilibrium.

Karen Elrayes 1L

Adding on to what everyone said. You are able to use ka to find kb because pka+pkb= 14 and ka + kb= 10^-14.

Karen Elrayes 1L

We only exclude solids and liquids. We usually exclude H2O because it is almost always the solvent, but since it is a gas it will be involved in the reaction and is, therefore, include in the k constant.

Karen Elrayes 1L

And to clarify, should we use 10^-3 or 10^-4 as the threshold to when we can ignore the +/- x to avoid a quadratic equation? Lavelle has mentioned both.

Karen Elrayes 1L

Will we be expected to figure out the formulas for the reactions on the exams, or will they be given?

Karen Elrayes 1L

When you go to saplings there is a link for atkins without the picture of the book itself and it's a pdf with all the answers

Karen Elrayes 1L

You should use it when you need to convert from pressure to concentration and vice versa and find the R constant that cancels out the proper units.

Karen Elrayes 1L

Reversing the reaction flips all Reactants to products and vice versa, thus when u are calculating K the top and bottom are flipped which is why we put 1/k when we reverse the reaction.

Karen Elrayes 1L

Kelvin is used because it has a bigger and more applicable range for the chemicals we are experimenting with

Karen Elrayes 1L

if they are all gases, you would most likely use Kp because gases aren't usually given in concentration. It also depends on the units you are given, so if you are given a value in concentration, you can convert everything to mol/l using the ideal gas equation PV=nRT

Karen Elrayes 1L

I'm a little confused with SO3. I know it is a lewis acid because it can accept lone pairs but what kind of bronsted acid/base is it. Because it can accept H+ protons right? So shouldn't it be a bronsted base? Also can it also donate lone pairs and act as a lewis base? I'm confusing myself :(

Karen Elrayes 1L

would an explanation be that s orbital is lower energy than p orbital so if s character of the hybrids increased then the energy would decrease meaning a decrease of electron density or the space the electron occupies has decreased causing an increase in bond angles?

Karen Elrayes 1L

What is meant by s and p character?

Karen Elrayes 1L

So just to clarify, the bigger the atom, the longer the bond, the more easily that bond is broken, so the stronger the acid? For example, HBr is stronger than HCl because Br is bigger than Cl?

Karen Elrayes 1L

I was literally about to come and ask that exact question. Thank you for the explanation!

Karen Elrayes 1L

What are the best methods to memorize all of this do u guys think?

Karen Elrayes 1L

What are all content we should have memorized for the final just so we have a list to go off of.

Karen Elrayes 1L

I hope they are fixed soon as well. But I'm glad that the issue isn't from my end. Thank you

Karen Elrayes 1L

Does anyone know who to reach out to because many of us are having difficulty watching the lectures through bruincast on ccle. They are not loading. It says error cannot load video. I even tried connecting to the ucla VPN and it still hasn't worked

Karen Elrayes 1L

Why is it okay for the lone pairs to be drawn next to each other in H20 but they have to be opposite each other in XeF4

Karen Elrayes 1L

Lone pairs have their own electrical density kind of like a bubble around them that causes repulsion

Karen Elrayes 1L

We don't really need sig figs currently because it is multiple-choice, but it is helpful to know for the future

Karen Elrayes 1L

Equatorial is kind of like the equator of the earth so it would help you visualize that they are the bonds on the horizal planes and axial are like the axis of the earth

Karen Elrayes 1L

It would be considered bent

Karen Elrayes 1L

Try to plan one day where you don't do anything school-related so you feel refreshed and ready to work throughout the week

Karen Elrayes 1L

Whenever there is more than one way to draw a structure by moving around the bonds, we have resonance

Karen Elrayes 1L

I honestly feel like it's best to write down everything you need to do for the week for all your classes and things you need to do outside of school. Writing them down makes you feel less overwhelmed and more motivated to finished one thing at a time. It helps focus your mind

Karen Elrayes 1L

After drawing the lewis structures, see which ones have resonance and those will be the ones that are delocalized.

Karen Elrayes 1L

Does anyone know if we can view the questions we got wrong on the midterm?

Karen Elrayes 1L

Is there a specific way to draw the lewis structures for ionic compounds instead of covalent?

Karen Elrayes 1L

Ahh yes that makes a lot more sense thank you

Karen Elrayes 1L

How can we compare or determine the strength of a dipole - dipole intermolecular force

Karen Elrayes 1L

also why are resonance structures more stable?

Karen Elrayes 1L

What is x-ray diffraction again?

Karen Elrayes 1L

Hey everyone, did professor Lavelle specify the cut off for the material on midterm 2?

Karen Elrayes 1L

"Electronegativity is the tendency of the atoms of an element to attract electrons when they are chemically combined with another element." So electronegativity deals with electrons from other atoms and not itself which is why it doesn't affect atom size. But as the rest of the posts said ...

Karen Elrayes 1L

Adding on to the rest of the posts, Lone pairs do not participate in bonding like everyone is saying but also they will help you keep count of all valence electrons. They are basically the valence electrons that aren't bonded with another element.

Karen Elrayes 1L

My friend is currently taking chem 14B and 14BL together and she said it was very doable. But when you are enrolling you have to enroll in 14B in ur first pass and 14BL in ur second pass for it to let you enroll.

Karen Elrayes 1L

In my opinion, going to step-up sessions, workshops is in itself self-study and preparing for the exam because that is where you will probably find out what you don't know as well as where you commonly make mistakes. I highly recommend going to at least 1 or 2 per week.

Karen Elrayes 1L

The exceptions H, He, Li, Be are exceptions because they tend to gain an electron or lose electrons to reach the s subshell meaning they are going to usually have 2 electrons in their outermost shell instead of the 8 which is what the octet rule suggests.

Karen Elrayes 1L

We don't need to do any problems from section topic 1C right?

Karen Elrayes 1L

Has anyone experienced an issue with the number of the posts it says we posted on the right? Because everytime I post it says its one post greater than how many I've actually posted

Karen Elrayes 1L

For the equation En= -hR/n^2 does the En represent the energy of an electron at the n energy level? and would that be equal to the energy of the light that excited that electron?

Karen Elrayes 1L

Do we need to know atomic and ionic radius trends for the midterm?

Karen Elrayes 1L

so is n1 actually n final? and n2 n intial?

Karen Elrayes 1L

Do you guys think we need sig figs since it's a multiple choice exam for this midterm

Karen Elrayes 1L

Light is a form of electromagnetic radiation, which consists of oscillating electric and magnetic fields that travel through empty space. As a light ray passes an electron (charged particle), its electric field pushes the electron first in one direction and then the opposite direction repeatedly, m...

Karen Elrayes 1L

What does it mean that an electric field pushes on charged particles causing them to oscillate? Like what does that apply to in what we have learned so far?

Karen Elrayes 1L

does anyone know what equations/values we should have memorized that aren't on the equation sheet?

Karen Elrayes 1L

How do we derive the Rydberg equation?

Karen Elrayes 1L

You definitely don't need to buy an external webcam. You can use ur phone to zoom and that will show ur workspace. It would be difficult to use ur computer webcam because you will be taking the exam on the computer and so you can't bend the laptop to show your workspace at the same time.

Karen Elrayes 1L

Just to clarify, the homeworks on sapling for week 2-4 are due week 4?

Karen Elrayes 1L

That's very reassuring thank you! I personally read through that chapter in the textbook and I know the basics of everything just don't have some memorized so I'm glad professor Lavelle isn't focused on us memorizing things.

Karen Elrayes 1L

How well do you guys think we should know all the nomenclature? Did you guys read through that chapter in sapling or take notes and flashcards and such?

Karen Elrayes 1L

Has anyone attended Dr. Lavell's office hours on Monday or Wednesday? Because I'm trying to join but I'm just stuck in the waiting room for quite a while. How do they work? Are we supposed to wait our turn or is it a discussion for everyone?

Karen Elrayes 1L

Are we able to redo the homework problems in sapling? Like are we given multiple tries?

Karen Elrayes 1L

Has anyone been to a workshop for this week? How are they structured? Like do we have worksheets to complete and like new problems or do have to bring our own question for it to be answered?

Karen Elrayes 1L

Where can I find the schedule and the zoom links for the step up sessions?

Karen Elrayes 1L

Also are you guys reading all the fundamentals or only the ones recommended in the syllabus?

Search found 101 matches