CHEMISTRY COMMUNITY

David Facio 3C

Breaking bonds is endothermic because it REQUIRES energy.

David Facio 3C

The graphs help you identify which value you will get for the constant k

David Facio 3C

Yes, they are interchangeable because C = coulombs, which is actually Joules / volt.

David Facio 3C

n is the number of electrons transferred during the redox reaction.

David Facio 3C

k will always be positive because it's a rate constant.

David Facio 3C

Steps: 1) Identify what is being oxidized and what is being reduced. 2) Split the original reaction into half reactions (one for reduction and one for oxidation reaction). 3) Balance all the elements except for Oxygen and Hydrogen. 4.1) If the solution is BASIC, First balance the Oxygens with H2O. T...

David Facio 3C

If the temperature of a gas decreases, then the gas molecules slow down and the internal energy of the gas decreases. This would result in a negative Delta U value.

David Facio 3C

This is similar to when something is in excess. We don't take that excess water into account because it is considered an aqueous solution, therefore it will not have a large enough effect.

David Facio 3C

Yes, K on it's own is the Equilibrium Constant, but it has many derivatives and they each can be used to determine different things such as:

K_eq , K_c , K_p , K_a , K_b , and K_sp

David Facio 3C

Study with someone who can teach you in terms you can understand. Sometimes a student perspective makes more sense and can relieve anxiety. This would also help the student who is helping you learn reinforce their own understanding.

David Facio 3C

Initially, you'd think since R is a constant, it should not change.

BUT it's important to remember that it can be one of two values, depending on which units are used:

R = 8.3145 if using units of J / mol K

OR

R = 0.0821 if using units of atm L / mol K

David Facio 3C

The best way to remember Gibbs free energy is to compare the equation to potential scenarios. Since \Delta G = \Delta H - T\Delta S "Gibbs free energy change = total energy change for the system - energy lost in disordering the system" Scenario #1) IF the Delta H < 0 & Delta S > 0 , TH...

David Facio 3C

Any time you see a capital "K", you should think "Equilibrium Constant" The subscript "w" denotes that you are dealing with the Equilibrium Constant of "WATER" You should be able to use the equation below to find the value of Ka or Kb (given that you're provid...

David Facio 3C

Yes it is possible for Delta U to equal zero. This is especially the case in a perfect insulated/isolated system.

Since U = w + q , If no heat energy is transferred and no work is performed, then the U value must be zero.

David Facio 3C

If you recall that the definition of a the equilibrium constant (K) is (P/R), then you can think of it logically as any other division problem. If the resulting variable is large, then you know there were more products than reactants. If the reaction moves forward, then you know it was more stable a...

David Facio 3C

Breaking bonds REQUIRES energy because if a molecule is already stable it wouldn't "want" to beak down.

Therefore, it is an endothermic process.

David Facio 3C

This might be a bit grim, but remember when Dr. Lavelle mentioned the bomb calorimeter and how it can be explosive if too much material, such as TNT, were to be added to the system. Maybe it's used to determine this exact type of energy exerted/work done by weapons in the military, just on a small s...

David Facio 3C

The best way to think about this is how free matter and energy are to exchange from the system to the outside universe. OPEN means both energy and matter can flow freely from the system to the outside. The system gets more restrictive with a CLOSED system because only energy can exchange and matter ...

David Facio 3C

So an easy way to remember is to think of this in relation to a system A reaction is EXO-thermic (as in EXO-skeleton, where exo is used to mean "outer" shell of arthropods) if q is negative (heat is released by the system OUTSIDE to the universe) A reaction is ENDO-thermic (as in ENDO-cyto...

David Facio 3C

Maybe something like cellular respiration in which our bodies break down glucose?

EX:

C6H12O6 + 6O2 → 6CO2 + 6H20 + energy

(Glucose + Oxygen → Carbon Dioxide + Water + Energy)

David Facio 3C

I think it depends on the specific problem your working on, since strong acids have high Ka values, but strong bases have low Ka values, and will both dissociate either way in water.

David Facio 3C

I think maybe not,

since the syllabus says to review problems 4C:1,7,9,11,13,15

:)

David Facio 3C

Definitely go to the step up sessions available beforehand! Speak up about anything you don't understand or have doubts about. We're all learning at our own paces. It's best to take advantage of the resources available to us.

David Facio 3C

I think unless the problem states that the conditions are not standard, then we can assume standard conditions.

David Facio 3C

Heat capacity also depends on mass. A larger bucket of water has a higher heat capacity than a smaller beaker of water.

David Facio 3C

I found this short video about Buffer solutions!

https://www.youtube.com/watch?v=jdmHjFp_35I

Unless it's specifically covered in lectures and discussions, I don't think we'll have to worry about it :)

David Facio 3C

Try logging out of achieve and log back in from it via MyUCLA.

Also, if its your browser, try it indifferent browsers, like safari vs google chrome

If none of those options work, try contacting the achieve website for troubleshooting.

David Facio 3C

Maybe increasing temperature causes the original molecule to dissociate and then the more reactants there are broken, the more products can be formed from it.

David Facio 3C

Yes, if not given a specific value in your word problem for room temperature, I'm sure that is a reasonable assumption.

David Facio 3C

I'm not sure why, but you have to pay attention to the numbers given in the problem. The significant figures correspond as follows: A whole-number pH corresponds to a concentration as a power of ten. A pH to one decimal place (like 5.2) corresponds to a concentration known to one significant figure....

David Facio 3C

Other than reading the textbook, does anyone have outside resources such as animated science youtube channel recommendations for visual learners?

David Facio 3C

Replying to part one of your question: I believe the autoprotolysis constant is unitless.

David Facio 3C

Can someone please explain the relationship between endothermic and exothermic reactions for adiabatic vs isothermal vs isobaric vs isochoric conditions?

David Facio 3C

I recommend attending the step-up sessions and reviewing the work performed from lectures and homework problems on Achieve!

David Facio 3C

So just to review, are there any special/important rules to remember when performing ICE box problems?

David Facio 3C

Just out of curiosity, does anyone know how to sequester carbon in soil? What exactly happens in the chemical processes?

David Facio 3C

I really recommend just being open with your TA's and Professor Lavelle and not being afraid to say what you don't understand. Attending office hours is really great if you need one on one assistance!

David Facio 3C

Does anyone know what food takes the longest to decompose? What material is it made of and how does it last for so long without spoiling?

David Facio 3C

You definitely should be reviewing lectures and asking questions here! The best way to learn is oftentimes to teach others and see if you understand the concept yourself! Peers are always willing to help! Also, Professor Lavelle has many practice problems listed on his website. Attending step up ses...

David Facio 3C

I personally recommend attending the PLF sessions offered by the AAP program! They've helped me with several other courses, including Chem 14A, the LS7 series and even the LS30 series! I always feel more comfortable knowing I'm in the hands of someone who has taken the course before.

David Facio 3C

I wanted to start off by saying this course was frightening for me at the beginning, considering I did not remember much from high school chem. The structure for this class was everything I needed, not only to review, but also to assimilate and appreciate the limitless amount of incoming knowledge f...

David Facio 3C

Professor Lavelle sent out an email on Monday December 14th, stating:

"By Saturday I should have all ~1,000 grades submitted for my 6 classes."

David Facio 3C

Course evaluations don't negatively affect your grade. However, course evaluations are offered for TAs and professors. If you feel that a particular course or instructor could benefit from an anonymous critique I recommend it. For the sake of other incoming students, giving some suggestions for impr...

David Facio 3C

I have a friend who TA'd for this class and said that this course is never curved. Like other students have posted, the syllabus also lacks any information or mention of anything about curving the final scores.

David Facio 3C

If I'm being one hundred percent honest, I have anxiety for every class I've ever taken at UCLA. Something about college and proving your worth via exams has always been nerve wracking for me. One exam does not define you. I just keep the end goal and my future in mind. I learned to always embrace t...

David Facio 3C

Acid-base conjugate pairs differ by just one H+ ion and always occur together For example, in the following scenarios: A) NH3 + H2O ---> NH4+ + OH- The conjugate base is OH- and the conjugate acid is NH4+ Similarly in B) HCl + H20 ---> Cl- + H3O+ The conjugate base is Cl- and the conjugate acid is H...

David Facio 3C

I agree with not letting your grade discourage you as we are not defined by them. However, I am feeling a bit anxious about the final exam. I totally bombed the first midterm, and I did earn a passing grade on the second midterm. So I feel like I have to earn the highest grade possible to make up fo...

David Facio 3C

At least biologically speaking, pH really matters for various systems. For example, we NEED strong acids in our digestive system to break down food, otherwise we'd not be able to extract nutrients as efficiently. However, enzymes denature in acids, therefore our bodies produce the sodium bicarbonate...

David Facio 3C

Think of it like the base you make when you lock arms with another person to give your friend a boost over a fence. If one of the persons serving as the base tried rotating their arms, it would be less stable, and under pressure, the base would break. Similarly, Pi bonds can't rotate, or else they'd...

David Facio 3C

I have logged out and back in to CCLE, but the error code: 232011 keeps popping up for both high and low bit versions of the lectures. Hopefully it get's fixed soon.

David Facio 3C

Correct me if I'm wrong, but I thought coordination compounds were a type of covalent bond. I think this has to do with the specific type of bond (such as single or multiple) that the compound has. We learned in Lecture 24 that whatever is [inside the bracket notation] means that it is inside the co...

David Facio 3C

For all VSEPR models, it is important to remember that lone pairs will always have the most repulsion over any bonds. This is especially the case for H2O, since its lewis structure contains TWO lone pairs. These two lone pairs have a combined repulsion that forces both the O-H bonds even closer toge...

David Facio 3C

I definitely agree that this class can be difficult at times, but thankfully we are under the tutelage of an amazing professor and assistant teaching staff. I know I performed horribly on the first midterm, but did better on the second. No one said this class was easy, but with the proper amount of ...

David Facio 3C

Normally, 5 regions of electron density would qualify as a trigonal bi-pyramidal shape, but since we have one lone pair, we know it is seesaw. If you imagine the lone pair atop the shape, and the rest of the bonds along the sides, then the bonds would all be pushed downwards, away from the lone pair...

David Facio 3C

I cook with my siblings and let my parents take the day off! My mom gets anxiety every year because the kitchen is her domain. I personally handle the ham and pineapple upside down cake!

David Facio 3C

Quizlet is definitely helpful, but I'm an old soul and I prefer flash cards. This way you can study anywhere without having to rely on a charged phone or laptop. Unfortunately I don't think this is something that acronyms or mneumonics will help with. I would definitely just have the structural draw...

David Facio 3C

We know that the Final exam will be cumulative, so I believe it's best to start preparing for it NOW! Think about it. We've already covered an insane amount of learning objectives so far, with more on the way. The best way to keep that information fresh in our minds is to revisit practice problems, ...

David Facio 3C

Rough guideline: In general, electronegativity increases up and to the right. Some charts/textbooks may have values for electronegativity that we don't have to memorize. If they are provided, then definitely use THOSE values given. If the electronegativity difference is > 2, then it is an ionic bond...

David Facio 3C

Unfortunately I live two blocks away from the 110 freeway, so I prefer not to go on runs near my house. I make due with some at home workouts. You'd be surprised what you can find on youtube! I try to workout at least 5 times a week, but between work, school and sleep it's sadly more like twice a we...

David Facio 3C

Today during Lecture #20, Professor Lavelle caught a typo in his notes regarding Li 2 CO 3 . He asked us as students if we knew what the mistake was, but I doubt any of us are on his expert level mode of chemistry knowledge. I was wondering if any of the students viewing his lecture caught it and IM...

David Facio 3C

The delta charges refer to the general area of a molecule where electrons are accumulated/clustered together, causing an unequal distribution or sharing of electrons. This can be due to different factors, such as electronegativity of a particular atom. The way to determine where to place the delta+ ...

David Facio 3C

I just want to clarify if you meant FORMAL charge of an atom? or deliberately meant FORMULA charge? We know formal charge is: FC = V -(s/2+L) V = # of valence electrons s = # of shared electrons and L = # of lone pair electrons However, It is important to remember that when calculating partial charg...

David Facio 3C

We know that London forces are always present within any molecule because of the chance that electrons will move to one particular region of the molecule for a short period of time. This creates the partial positive and negative charges we observe in London (dispersion) Forces. I went about a simila...

David Facio 3C

If you've ever taken or plan on taking the LS7 series, you know or will learn that London (aka Van der Waals Forces) are present in every type of molecule. London dispersion forces occur because of partially negatively charged regions and partially positively charged regions. Take the interaction of...

David Facio 3C

The best way to think of this is with the Ammonia example from Lecture 19: Visually, the lone pairs atop the model take up the most volume because they have the MOST repulsion. Secondly, the space between the lone pairs and the bonded hydrogens is less than the aforementioned repulsion between lone ...

David Facio 3C

The easiest way to differentiate between these two is to write out the full electron configuration and the condensed electron configuration. Here's an example for the element Mn: Full: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 5 Condensed: [Ar] 4s 2 3d 2 From the configurations above, you can figure out the ...

David Facio 3C

Every day, I'm surrounded by seven insanely loud children of varying ages in my household. No one appreciates a library more than I do! I completely agree that studying from home is a lot more difficult now, especially if you need privacy and silence to focus. I've been able to study best late at ni...

David Facio 3C

During one of my step up sessions, the instructor mentioned that since chlorine is in Period 3, it can have an expanded octet because it has empty d-orbitals that can hold extra valence electrons. Additionally, they stated that since fluorine is in Period 2, it does NOT have any d-orbitals, therefor...

David Facio 3C

I think you would have to take into account the formal charge of each individual element to make sure you have a stable Lewis structure, as well as the actual charge of the overall molecule. If the Lewis structure you are working with is in fact an ion, then it should form ionic bonds with Lewis str...

David Facio 3C

Professor Lavelle said it's not necessary to memorize things like this. Rather we should feel comfortable figuring out the charges by using the periodic table. If you feel more comfortable memorizing them, more power to you! :)

David Facio 3C

In general, the elements on the far left side of the periodic table like Li, Na, K, Rb, Cs, and Fr have LOW ionization energy and the elements on the far right side like F, Cl, Br, I, and At have HIGH electron affinity right? So would it be incorrect to say these groups of elements have an inverse r...

David Facio 3C

While on the subject of the midterm, I wanted to ask a concern of mine. I entered the Respondus web-lock browser and opened the link for the midterm, but when I entered the zoom link for my TA's discussion, the screen was white. I exited the zoom meeting and attempted it again, and got the same resu...

David Facio 3C

I think as you fill up your orbitals, you must fill them all up in the spin up position, and then fill them in the spin down position when pairing.

David Facio 3C

I remember Professor Lavelle telling us that the mid range for visible light is about 500 nm, and from there I remember that Violet Light is 420 nm and it's opposite on the other end of the visible light spectrum is Red Light at 700 nm. Infrared radiation is not nearly as harmful as UV radiation, an...

David Facio 3C

My TA recommended since Week 1 that we differentiate our variables with specific font. You may choose to exaggerate your "v" for frequency by writing it in cursive or even write it like the zodiac symbol for aries. Whatever helps you visually remind yourself NOT to mix it up with the regul...

David Facio 3C

I listen to music, dance, hit up friends to make sure they haven't died, watch movies, exercise, and nap. All are great ways to relax!

David Facio 3C

Quantum Numbers Principle: (n) Angular Momentum: (L) Magnetic: (m_l) Spin: (m_s) The second shell (n=2) has two subshells (L= 0 and L= 1) L=1 is the p-subshell and it has three possible orbitals where m_l can be (-1, 0, 1) I think for that example he was saying that the value of -1 specifically tel...

David Facio 3C

I think it would be prudent to fully understand unit conversions. It will not only be beneficial for the midterm, but also for other classes you may take in the future. We still have a whole weekend left before the midterm. I recommend reviewing SI conversions if you have the time to squeeze it into...

David Facio 3C

Orbital properties allow us to calculate the PROBABILITY of encountering an electron. Professor Lavelle went through it quickly in Wednesday's lecture and to be fair, it is complicated, even visually. Schrodinger's equation let's us use a wave function to describe an e- in an atom. psi (trident look...

David Facio 3C

I go about it by asking myself whether I fully understand the concepts. If I know that I don't have a full grasp on the conceptual, I review the lectures, textbook, and modules on Prof. Lavelle's Chem 14A website. If that still isn't sufficient, I would recommend attending office hours and step up s...

David Facio 3C

Yes, I concur with everyone else. Both TA's and LA's have unanimously recommended completing the problem with full values for calculations, and then applying sig fig rules to your final answer. This ensures the most accurate answer. I was confused by this for a while too! Great Question!

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