CHEMISTRY COMMUNITY

keely_bales_1f

I don't think we need to know too much about catalysts for the exam, but they are not consumed. I wouldn't stress too much about this topic. However, if you are curious, I attached an article that goes into a more in depth description of catalysts. http://ch302.cm.utexas.edu/kinetics/catalysts/catal...

keely_bales_1f

I assume that this would be the case however I am not completely sure. I would say to just get all your posts in today before midnight just to be safe.

keely_bales_1f

And for the second part of this question, you would do the same thing essentially, just switching the values you use. For example, you would do (3^1)(0.5^2)(initial rate given).

keely_bales_1f

Everyone above described a catalyst vs intermediate very well. I just thought I would give an example, so you can see their definitions in action... A+B-->AB AB+C-->AC+B Based on these equations, we can see that AB is an intermediate, for it is first produced, then consumed. Species B is a catalyst ...

keely_bales_1f

I would review the sapling problems from week 1 to week 10, and see the equations you used to solve those problems. I would do this while looking at the equations sheet. For example, read a question and refer to the equation sheet just to practice and get familiarized with the location of where ever...

keely_bales_1f

Dr. Lavelle, I wanted to write and say thank you for teaching me about chemistry for the past two quarters. Your videos, or lectures, always started off with music, that made my mornings that much sweeter (#djlavelle). I hope one day we can meet in person on campus, and exchange some chemistry puns!...

keely_bales_1f

How do you laugh in a "chemist's" language?

HeHe

keely_bales_1f

Its crazy to think that any cooking we do involves chemistry. Like even cutting an avocado in half sets off a chemical reaction that changes the green flesh of the avocado to a brownish color. CRAZY

keely_bales_1f

I feel that everyone above did a great job explaining, but just thought a summary of equations could be useful to you all! I attached it below :)

keely_bales_1f

As students above have mentioned, Gibbs free energy combines enthalpy and entropy into a single value. If delta G is negative, the reaction is spontaneous. If delta G is positive, the reaction is non-spontaneous. When delta G is equal to 0, the system is at equilibrium.

keely_bales_1f

I distressed by eating at my favorite sandwich shop. Then taking a nap when I got home, and then watching wandavision when I woke up :)

keely_bales_1f

To solve this question, you just need to balance the two half reactions individually before putting them together! Cr -> CrO 4 2- Balance O using H2O: Cr + 4H 2 O -> CrO 4 2- Balance H using H+: Cr + 4H 2 O -> CrO 4 2- + 8H + Balance charge using e - : Cr + 4H 2 O -> CrO 4 2- + 8H + + 6e - Cu 2+ ->...

keely_bales_1f

Lorraine Jiang 2C wrote:Hi! I had the same issue but I fixed it by putting H2O as the last item on one side of the equation.

Hope it helps!

Omg I am going to try this and hope it works. I swear I have the right answer, just going to rearrange it now!

keely_bales_1f

Would we be able to determine how strong of an oxidizing agent an element could be by looking at the periodic table?

keely_bales_1f

Hi Adam! I started by writing the unbalanced equation with the reactants on the left side and products on the right. The question states that "rust is caused by iron reacting with oxygen gas in the presence of water to create an oxide layer." So the reactants would be Fe + O2 + H2O. Then ...

keely_bales_1f

I really enjoyed my communications class this quarter, COMM 10. It was super interesting and pretty easy. I also enjoyed my literature class, ComLit2CW with professor Komar. It satisfies your diversity requirement and one other requirement (I think your analysis one?), but it is a lot of heavy readi...

keely_bales_1f

Popcorn and cinnamon toast are my favorite comfort foods. They always are delicious for any occasion.

keely_bales_1f

Heat and Work are not state functions because they are dependent on the path used to go from the initial to final state. State functions by definition only depend on the state of the system, not the path used to get to that state. I hope this explanation was somewhat helpful!

keely_bales_1f

As students have mentioned above, the R constant you use depends on the context of the problem!

keely_bales_1f

Yes we love Wanda Vision! I just plan on getting outside, maybe the beach because the sound of the waves crashing on the shore is so therapeutic.

keely_bales_1f

I am super worried for finals this quarter because chemistry is a lot more complex this quarter (thermochemistry is the death of me!). However, power naps and watching comedic relief shows on Netflix or Hulu help relieve some anxiety.

keely_bales_1f

I followed the correct steps (and the same ones I followed for part b), but keep getting a very large number for k. Any idea why this might be? I had the same problem. have you checked all the signs of your values? I realized I didn't carry a negative sign from one of the table values which gave me...

keely_bales_1f

No you do not! I believe that they are on the equation sheet.

keely_bales_1f

Depending on the context of the problem you might have to convert a few things, including temperature. Just make sure you pay attention to the wording and context of a problem because it can be the difference between a right answer and a wrong answer!

keely_bales_1f

A closed system can exchange energy with its surroundings (not matter like in an open system), whereas an isolated system cannot exchange matter with either its surroundings nor matter.

Example of Closed System: putting ice on injury
Example of Isolated System: sealed vacuum flask

keely_bales_1f

What's the difference between and optimist, a pessimist, and a chemist?

An optimist sees the glass half full, a pessimist sees the glass half empty, and the chemist sees the glass full with half liquid and half gas.

keely_bales_1f

The way to solve for ΔU also depends on the molar specific heat of the gas. For q, you use the constant-pressure molar specific heat, which you are given as 4R. However, the equation for ΔU is ΔU = nCvΔT The ΔU equation requires the constant-volume molar specific heat. So how are constant-pressure ...

keely_bales_1f

The first path is a reversible expansion so you would use w = -nRTln(V2/V1). However you first need to find moles so you would use the ideal gas law to find it (n = PV/RT). Then once you solved for moles you input it in -nRTln(V2/V1). For Path B because it is at a constant pressure, irreversible re...

keely_bales_1f

Although great answers have been said above, I will reiterate what they stated. First use stoichiometry to calculate the number of moles of N2 produced. Second use the PV=nRT equation. (Your value for R in this scenario will be 0.0821, the value for your temperature must be in Kelvin...) Third, with...

keely_bales_1f

As what other students mentioned above, the many different R values are used depending on the situation of the given problem. I was confused too with all the different R values!

keely_bales_1f

As said above, ask questions on chemistry community! Or even in the Chem GroupMe app. Adila helps answering a lot of people's questions. Don't Gove up! You got this :)

keely_bales_1f

Last quarter I struggled with the Lavelle's tests even after studying the best I knew how to. However, going to all the UA sessions helped a lot. As did doing the textbook questions. I too am worried about grades, but remember that we still have two more exams in this class that we can improve upon!...

keely_bales_1f

To relax I usually listen to music!

keely_bales_1f

Gold is the best element. Why you ask?

Because it is AU-some.

keely_bales_1f

An ice cube with a mass of 50.0 g at 0.0 ∘C is added to a glass containing 387 g of water at 45.0 ∘C. Determine the final temperature of the system at equilibrium. The specific heat capacity of water, Cs is 4.184 J/g⋅∘C and the standard enthalpy of fusion, ΔH∘fus of water is 6.01×10^3 J/mol. Assume ...

keely_bales_1f

Definitely put in the hours to study. I would read the sections of the textbook he assigned in the outlines, as well as the textbook problems. In addition UA session are super helpful!

keely_bales_1f

I would definitely review materials for chem 14a if you had Lavelle, specifically strong acids and bases. This made identifying acidic, basic, and neutral so much easier! I believe a list of the strong acids and bases is on Sapling as well.

keely_bales_1f

The values of x, or rather the quantity of it, does correspond to the stoichiometric coefficients of the balanced chemical equation.

keely_bales_1f

I took a meditating fiat lux class in the fall and it definitely helps me relax. It is nice to just sit and breathe for a minute, and not have to think about anything in particular. If you are interested in meditation I would definitely recommend taking Professor Shorter's Meditation fiat lux if he ...

keely_bales_1f

Criminal Minds is always good (if you're into criminology and profiling). If you're looking for something that is more upbeat and funny, I feel like New Girl and Impractical Jokers never fail to make me laugh. As for childhood shows, Big Time Rush was one of my favorites. I also really enjoyed Julie...

keely_bales_1f

What's the dullest element?

Bohrium!

keely_bales_1f

Smaller than 10^-3 he said!

keely_bales_1f

Yeah I was having similar thoughts. I feel that this would be a good question to bring up to Professor Lavelle during his office hours for a clear and distant answer. (If there is a distinct answer.)

keely_bales_1f

Depending on the context of the problem, Kw can be used in a multitude of ways. However, primarily it is used to find the H3O+ and the OH- concentrations. ( [H3O+][OH-]=Kw=1.0 x 10^-14 ) If you are given the pOH of the pH and need to find the other, you could used this equation: pH + pOH = 14. If yo...

keely_bales_1f

In Dr. Lavelle's lectures for week 1, he covers that chemical reactions adjust to minimize the effect of changes... Le Chatelier's Principle. He also says that Le Chatelier's Priciple applies to changing physical parameters (Pressure and Temperature). I would definitely review that last section of t...

keely_bales_1f

what do you do with a sick chemist?

if you can't helium, and you can't curium, you might as well barium.

keely_bales_1f

To know which value of R to use, make sure you read the problem that you are doing carefully. It should give you context clues as to whether you are dealing with atms, bars, etc. Then you would use the R value for the specific unit.

keely_bales_1f

By increasing the pressure (only applies to gases), you would be decreasing the overall volume. This would result in an increase of concentration.

keely_bales_1f

So if we are given Kc and then are told to calculate Q with the given concentrations of the products and reactants, Q would tell us if the reaction is at equilibrium or if the reaction leans toward the products/reactants?

keely_bales_1f

I would look at the responses written under the tab of Sapling Problem #5 (Of this section) because students have given very detailed and helpful answers there!

keely_bales_1f

When looking at this problem yesterday I had no idea how to do it. After my discussion session today where we did a similar problem, I now understand how to go about this problem. First you need to figure out which equations listed have the reactants and products you are looking for (know that you c...

keely_bales_1f

I believe that Professor Lavelle will go into more detail about titrations in Chem 14B. But based on the last lecture in 14A, the graph he depicted was a titration curve. It showed us the volume of the titrant on the x-axis and the pH on the y-axis. This graph also tells us the stoichiometric or equ...

keely_bales_1f

The chemistry 14A GroupMe group chat converted into a Chem 14B group chat. Let me know if you need the link to join!

keely_bales_1f

Are there a lot of topics in the book that are not covered during lecture that show up on tests? I feel that on the midterms, doing the practice problems from the textbook helped a lot. So for next quarter I recommend keeping up with textbook material as it is being taught in lectures. I feel that ...

keely_bales_1f

As stated above, Lewis acids/bases have to deal with electrons whereas Bronsted acids/bases deal with H+ ions.

keely_bales_1f

Hey you guys just remember that it is many of your first quarter at UCLA with everything being virtual. Try not to stress to much!

keely_bales_1f

What do you call and acid with an attitude?

A - meano - acid :)

keely_bales_1f

The Roman numeral after the metal, written in parenthesis, represents the oxidation state of that metal.

keely_bales_1f

As someone had already said above, the two definitions describe an acid, but the Bronsted definition deals with the protons and the Lewis definition deals with the electrons. I find that reading the textbook clarified these two definitions.

keely_bales_1f

I am not quite sure when we will receive our final grade, but I assume it will be shortly after we take our final exam.

keely_bales_1f

The answer is just octahedral. Octahedral is a COMMON shape for the coordination number 6. I think when I looked at the explanation for this problem it said that pentagonal pyramidal was not common.

keely_bales_1f

Yes! Ligands must have one or more lone pairs. Just a bit of extra information that Lavelle covered in his last lecture (11/26/20) that we need to know is: Ligands bind at: 1 site (donate 1 e- pair) --> Monodentate 2 sites (donate 2e- pair) --> Bidentate 3 sites (donate 3e- pair) --> Tridentate 6 si...

keely_bales_1f

In Lavelle's last lecture (11/26/20), he said that the number of bonds was equal to the coordination number.

keely_bales_1f

I am pretty sure we don't need to know what these orbitals look like, rather we just have to know what the hybridization of a molecule will be based off the number of electron densities present on the central atom. However, I would ask this question in office hours with Lavelle to double check!

keely_bales_1f

Hi I found this really good website to study the VSEPR chart. http://intro.chem.okstate.edu/1314F00/Lecture/Chapter10/VSEPR.html Yes! This is the website the Justin recommended during his workshop and it is really helpful for visualizing the molecular shapes. He just reminded us to double check the...

keely_bales_1f

What exactly makes single bonds capable of rotation and double bonds unable to do so? I definitely would rewatch Lavelle's Week 7 Friday Lecture (11/20/20). He draws out sigma and pi bonds and does a demonstration with a pencil that explains why double bonds are incapable of rotating. I have attach...

keely_bales_1f

When I went to Justin's UA session, he said that we are not required to know the exact angle. However, we are supposed to give an approximate angle, such as less than or greater than 90 degrees.

keely_bales_1f

The answer would be square planar! Check out the website I linked below for more help with identifying molecular geometry!
http://intro.chem.okstate.edu/1314F00/L ... VSEPR.html

keely_bales_1f

I usually have intermittent dance parties in my room throughout the day. I also watch youtube dance videos and try and copy the choreography, but I am not the best dancer. I try and run but finding the motivation to run can be hard.

keely_bales_1f

Remember, if you struggled with these topics, try and go to as many step-up and UA sessions as possible. They are honestly such a HUGE help since they go over more complex examples and relate it back to the concepts Lavelle discusses in lectures. We also still have a final to take! Try not to stress...

keely_bales_1f

As everyone said above, pretty sure we will still have lectures and discussion sections as scheduled up to Wednesday, but since we have Thursday and Friday off, I would say there are no discussion sections / lectures scheduled. However, I would wait and watch Monday's lecture and keep and ear open f...

keely_bales_1f

When I went to Justin's UA session, he said that we should know more shapes just to be safe, but also to help us prepare of organic chemistry. He shared a link with us during his Saturday session which allows you to see a visual of each of the shapes in the VSEPR Model. I have attached the link belo...

keely_bales_1f

I would definitely recommend reviewing the lectures from Lavelle since he covers all the trends we should know for the upcoming midterm.

keely_bales_1f

If you want more clarification for atomic radii, I would look at the period table that Lavelle had put in his lectures. I have attached the link to a similar one below... I hope this helps! https://www.google.com/url?sa=i&url=http%3A%2F%2Fcrystalmaker.com%2Fsupport%2Ftutorials%2Fatomic-radii%2Fi...

keely_bales_1f

For the midterm I am reviewing my lecture notes, doing practice worksheets from the UA sessions, and working on textbook problems. I personally like making flash cards for each of the concepts on the outlines, to know what I have to study more.

keely_bales_1f

Before the exam, you can only have a periodic table that is on Lavelle’s website. However, once the exam starts you can draw whatever you want on the period table, including trends and the line that distinguishes metals from non metals in the p-block.

keely_bales_1f

I had a clarification question about Lewis Acids and Bases. I know that Lewis Acids accept an electron pair and a Lewis Base donates and electron pair. I also know that acids and bases combine to form a coordinate covalent bond. I was wondering if there is a trick to identifying Lewis Acids and Base...

keely_bales_1f

I feel like worrying about grades is common grounds for all students, especially us UCLA overachiever students. However, just do your best because that's all you can do. But if you continue to worry, it's all good. Only 4 more weeks to go!

keely_bales_1f

I am not sure up to exactly where in the textbook (for Midterm 2), however, completing the problems that are covering the same topics as lectures would be the safest bet. As well as following the outlines.

keely_bales_1f

I found this image that has a summarization of periodic table trends. I have attached the image below. Hope you find it helpful!

keely_bales_1f

This is amazing! I will definitely join this group me to get as much extra help and studying in as possible.

keely_bales_1f

This year I have been taking a meditation course that has been helping me with my anxiety. Just taking a few minutes out of your day to focus on your breathing has been a big help for me personally. However, if you have more final jitters regarding content, making a study guide and a study group wou...

keely_bales_1f

Did you convert from meters to nanometers correctly? Or did you type an error into your calculator by accident? Those are the only issues I can seem to think of.

keely_bales_1f

To solve this problem you must first use the equation E=(hc)/lamda. Once you find the energy using this equation, convert to electron volts. (This constant value can be found on the Constants and Equations Worksheet provided by Lavelle.) Then make sure you take the difference of this value that you ...

keely_bales_1f

In Lavelle's lectures, he talked about what each of the variables represent. I believe it was his week 3 Friday Lecture. I have attached a picture that should help with this problem.

keely_bales_1f

When answering this problem, remember that the wave must interfere constructively with itself. In other terms, it must be complete wavelengths. (Whole number of wavelengths).

keely_bales_1f

When solving this problem, the 2.4 micro meter is the wavelength. So knowing this, you can still use the E = hv equation, but you also must use the c=wavelength(frequency) equation to substitute your known variables to find the energy of the photon. You will eventually get E=h(c/wavelength). When yo...

keely_bales_1f

How do we know what will be on the midterm please help i am freaking out. Is there a place where we can figure this out or do we just go to office hours. The syllabus has a bunch of practice problems that Lavelle recommends doing. Those questions are fair game for the midterm, so I would definitely...

keely_bales_1f

It's still a bit unclear about the amount of material we are able to use for the midterm; I thought I heard he was going to provide a printout sheet for the formulas, but I have not gotten an email about this. We are able to use a sheet of constants and equations that he provides to us and a period...

keely_bales_1f

Are we able to use graphing calculators for the midterm? I heard some TAs are accepting them but I'm not sure if this is true for every section. I am pretty sure if you have a graphing calculator (the TI-84), it is acceptable. My TA said that because the majority of students have that calculator fr...

keely_bales_1f

Professor Lavelle does go over a lot of high school chemistry, but he didn't go over nomenclature. He also said all necessary tools to solve a problem will be given to us on an exam. However, when doing examples in my discussion session with my TA, she says that a lot of molecular compound names sho...

keely_bales_1f

On the constants and equations worksheet from Professor Lavelle's chem14a website, there is something listed as "1 atm = 101.325 kPa"
Could someone please explain what this means?

keely_bales_1f

In the lecture on Wednesday (10/21), Professor Lavelle was talking about orbitals. He mentioned that orbitals p, d, and f have a nodal plane. Could someone explain what a nodal plane is please?

keely_bales_1f

Hi! When two waves are in the same path, energy is always conserved and the end results will depend on the waves. For constructive waves, two waves will combine energies together usually because they are in phase (their crests line up), ultimately increasing the amplitude of the wave. The opposite ...

keely_bales_1f

What is the actual reason for the fact that shorter wavelength/higher frequency light can eject electrons but longer wavelength/lower frequency light cannot? Each photon must have enough energy to eject an electron, and low frequency light has no photons with sufficient energy to f=do this. Increas...

keely_bales_1f

Just remember that Balmer series is in the visible region whereas the Lyman series is in the UV region. I also attached a diagram that was included in Lecture 6 that I drew out in my notes. I hope you find it helpful!

keely_bales_1f

Also regarding exams, I wanted to confirm that constants will be given to us. This is correct right? Because I remember him saying that we didn't need to memorize constants in one of our lectures.

keely_bales_1f

When I went to Lavelle's office hours, he said that there was an app that we needed to install on our computer order to download the textbook onto our computers. Does anyone know what app this might have been?

keely_bales_1f

In my discussion class, my TA said that 0.500g is only 1 significant figure. I am pretty sure it was 3 significant figures, but I just wanted to double check here. I'm certain 0.500 has 3 significant figures because trailing zeroes are taken into account because there's a decimal point. Leading zer...

keely_bales_1f

In my discussion class, my TA said that 0.500g is only 1 significant figure. I am pretty sure it was 3 significant figures, but I just wanted to double check here. The Sig figs sheet on Lavelle's website states that trailing zeros with a decimal point are counted as significant. Take a look at that...

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