CHEMISTRY COMMUNITY

Truman Chong Dis 3G

Some of my Comfort movies are the Star Wars Original trilogy along with Episode 3. In addition, I really like watching the Iron Man Trilogy and the Hobbit movies. For music in the background, try to pick something that you like and easily gets stuck in your mind. It helps for memory retention and re...

Truman Chong Dis 3G

Does anyone know when the Chemistry Community posts are supposed to be done by each week? I know we are supposed to have posted five times each week, but what day are our posts actually due? Chem Community Posts are due every Sunday by 11:59pm. Some TAs are more lenient but this generally the rule ...

Truman Chong Dis 3G

As someone who didn't take 14A with Lavelle how is the midterm formatted? Last quarter the midterms were held on a program called Respondus Lockdown Browswer and the actual test was all multiple choice. Additionally, we had to have a camera or secondary device that showed our workspace. I would exp...

Truman Chong Dis 3G

I'm not completely sure what you did but I believe your x-value is wrong. Some tips to make sure your doing these types of questions is to remember if the reaction when balanced has the products have a coefficient greater than 1 then remember when going through the reverse reaction to subtract 2x no...

Truman Chong Dis 3G

Considering that so far there has been a lot of math involved in 14B, I think really the best way to study once you understand the concepts is to do practice problems. I believe that we are able to use a calculator for this class and it would be important to have good handling of your calculator if ...

Truman Chong Dis 3G

I believe combustion reactions do not reach chemical equilibrium but are able to reach thermal equilibrium. This just means that the reaction stops when the heat energy of the products equal to that of the reactants. However, the reverse reaction cannot occur as combustion reactions are non-equilibr...

Truman Chong Dis 3G

Not that I know of. Currently, at least on my CCLE page for 14A the final says review not permitted. I'm not sure if Professor Lavelle is allowing this but you could possibly email him and ask for an appointment or something if there is anything specific about it you need answers for.

Truman Chong Dis 3G

Helium walks into a bar,
The bar tender says "We don't serve noble gasses in here."
Helium doesn't react.

Truman Chong Dis 3G

I find it helpful to spread things out a lot as to not overwork yourself and experience burnout. It helps to divide up the topics into sections and slowly tackle each sections when it comes to studying. Additionally, regularly try your hand at practice problems even when you haven't studied a partic...

Truman Chong Dis 3G

If possible I would definitely try to do as much practice as possible especially through the textbook questions. I would try to exhaust every possible resource that Professor Lavelle has provided for us such as the UA sessions, and office hours. For studying for the midterms, the outline serves as a...

Truman Chong Dis 3G

I really wanted to get into [censored] study habits Fall Quarter but that didn't really work out as I regressed to large amounts of procrastination. However, going forward I want to try to plan out my week the weekend before to give me an idea of the blocks of time I need to set aside and do purpose...

Truman Chong Dis 3G

I think Dr. Lavelle emailed saying that he would be able to post all the grades for the final by Saturday so I would assume some time early next week.

Truman Chong Dis 3G

I don't think it counted for any points in this class so I wouldn't worry too much about it. It was just an opportunity for students to give professors and TAs some feedback about the class and how it could possible change. I would check MyUCLA in case it is still open and you can fill it out there.

Truman Chong Dis 3G

I thought the final was a bit of a time crunch especially compared to the midterms. By the time I got to the halfway point, I could tell that I was way behind with not enough time left. I definitely couldn't spending as much time as I usually did to contemplate each question and try different method...

Truman Chong Dis 3G

I'm probably going to be binge watching Netflix shows while snacking 24/7.

Truman Chong Dis 3G

Negative poles in between molecules depend on the shape and the symmetry of polar bonds. For example with COF2, the general shape is trigonal planar and since C-F bonds are more polar than C=O bonds due to respective electronegativity differences, the symmetry would be off as the polarity of C=O can...

Truman Chong Dis 3G

If you like anime so good shows are Demon Slayer, That Time I Got Reincarnated as a Slime, and Mob Psycho. My favorite show from when I was a kid were Doraemon, Gravity Falls, and Teen Titans.

Truman Chong Dis 3G

Molecules with only nonpolar bonds cannot be polar as there is no large enough charge separations in different regions of the molecule. However, you can have temporary dipoles due to London Dispersion forces which depend on molecular size and mass.

Truman Chong Dis 3G

I believe polarity is a result of both the bonds and the shape. Shape determines the orientation and symmetry of the molecule; however, the electronegativity difference in the bonds helps determine the polarity when the outer atoms are different from each other. So depending on how the shape orients...

Truman Chong Dis 3G

If you think about the shape completely bonded to atoms, an atom with only 4 bonding regions would create the general structure of tetrahedral. Now imagine that you take away two of those atoms, the resulting shape left by the remaining atoms would be a bent structure with the non-bonding region whe...

Truman Chong Dis 3G

I don’t think we need to know this for the class. But for the sake of your question I searched it up and I found that it has to do with considering orbitals as wavefunctions as using calculus to to determine orthogonality and normalization. However, as basic concepts that may or may not end up being...

Truman Chong Dis 3G

I find that listening to some up-beat pop music always helps to relax me. But honestly, any music that you like would probably help you relax and ease your anxiety slightly.

Truman Chong Dis 3G

By no means is this the best method, but in a pinch I generally think of the structures as different intersecting circular planes and by dividing 360 by the number of atoms on the circular plane to get the angle between them. However, this is assuming all bonding domains are occupied so you would al...

Truman Chong Dis 3G

Lone pairs occupying the equatorial region over the axial region in the trigonal bipyramidal structure has to do with the optimization of the structure to have the smallest amount of repulsion. This leads for the equator to start losing lone pairs first as the equatorial plane would only have two ne...

Truman Chong Dis 3G

In structures with many bonds I think its best to imagine the structure in 3D with the lone pair generally have the most effect on the bond angles between atoms on the same plane. Due to lone pair repulsion, the other angles will end up slightly smaller than normal and the angle between the lone pai...

Truman Chong Dis 3G

After the 3d orbital starts to get filled, it actually is lower in energy/more stable than 4s. Additionally, if you consider the octet rule, 3d would not necessarily be in the valence as it is of a lower energy level than the n=4 energy level. Therefore, the electron would come out of the 4s orbital.

Truman Chong Dis 3G

You can find the formal charge for each atom in the structure by counting the number of lone pairs and bonds made by each atom. One lone pair counts as 2 electrons and one bond counts as 1 electron. Then compare it to the valence that the atom would normally have. If the atom has more than normal, t...

Truman Chong Dis 3G

The "non-favorable" structures and favorable structures are both included in making the resonance hybrid since the hybrid is a representation of all structures in one with variable bond changes represented by dotted lines.

Truman Chong Dis 3G

Atoms in the 3p-block can have an expanded octet too as the 3d block exists in addition to 3a and 3p which is the same idea that energy levels coming after n=3 can also have the the s, p, d blocks. The idea that the 3d block comes after the 4s is due to the slight energy difference between the 3d an...

Truman Chong Dis 3G

A resonance hybrid is a the combination of all resonance structures in one with all the variable bonds represented by dotted lines. The individual resonance structures show one possible construction of the bonds which is one of many combinations that contribute to the overall structure. The hybrid i...

Truman Chong Dis 3G

I believe it has to do with symmetry not just bond polarity. Even though the individual bonds between B and F are polar, the symmetry of the overall molecule allows the polar bonds to balance each other out making the over distribution of electrons equal and and cancel out, creating a nonpolar molec...

Truman Chong Dis 3G

Adding to what others have already said, hydrogen bonds occur intermolecularly when at least one of the molecules have an O-H, N-H, or F-H bond. The other molecule must also have some sort of polarity either from being an ion, polar molecule, or partial charges. Polarity normal occurs when there is ...

Truman Chong Dis 3G

More resonance structures allows a molecule to be more stable than less resonance structures because since all of the resonance structures exist at the same time, it allows the formal charges to be more spread out among the various different bonds capable of being formed in the different resonance s...

Truman Chong Dis 3G

I'm not entirely sure about this, but I assume that structure and size would get in the way of multiple hydrogen bonds being formed as depending on orientation there would be more than just plain hydrogen bond interaction. It is possible that molecules may not be small enough to properly form a hydr...

Truman Chong Dis 3G

The octet rule is the general idea that atoms can only hold 8 electrons in their valence shell. This idea helps when determining Lewis structures for molecules in terms of the number of bonds/ lone pairs each atom can have. However, there are many exceptions including how atoms n=4 and above are abl...

Truman Chong Dis 3G

Like Sabrina said, it would be easier to tackle this problem using ν= R[(1/((n1)^2))-(1/((n2)^2))]. If you choose to use En= -((hR)/(n^2)), n would be 3 and 1 respectively so the denominators would be 9 and 1 not 8 and 2. Continuing on this path you can use ΔE= E(final)- E(initial). Then instead of ...

Truman Chong Dis 3G

You can solve these problems using the Rydberg equation. Where n1 is the lower energy level and n2 is the higher energy level. Based on the context of the question you need one or the other to properly solve for the other. In terms of light emitted, it is determined by the the energy level that the ...

Truman Chong Dis 3G

Electronegativity and Electron Affinity are similar but not the same. Electronegativity is the chemical property of an atom relating to its ability to attract electrons from another atom. Electron Affinity is the amount of energy released when an electron is accepted by a neutral atom. These are als...

Truman Chong Dis 3G

I don’t think direction matters for Hunt’s rule as long as electrons in different orbitals are the same direction. For example, writing p^3 you would have 3 arrows in 3 different orbitals all pointing in the same direction to maximize spin.

Truman Chong Dis 3G

I’m not quite sure what was your work for this problem but here’s what I did. For the Rydberg formula, I noticed that n1 should always be the smaller energy level number (in this case 1); therefore, n2 would be 2. Plugging in the values, squaring them, and then subtract them. After multiplying by R ...

Truman Chong Dis 3G

The general trend is increasing as you move to the right and up. However, the noble gases are excluded.

Truman Chong Dis 3G

I’m not sure if you have the same problem as me with my TI-83, but write down your in between answers when doing calculations because the calculator doesn’t allow you to scroll up. Unless possibly mine is just faulty...

Truman Chong Dis 3G

I don’t think it’s necessarily required unless there is a phase change/ phase difference between products and reactants.

Truman Chong Dis 3G

I recommend keeping all values in your calculator until the final solution and round using the number of sig figs in the question.

Truman Chong Dis 3G

I think you may have mistaken E= hc/λ for E=hc/v. E=hc/λ is the same as E=hv where v is substituted using the equation c=λν solved for v. E=hv and c=λν can be used in conjunction with each other to find E, λ, or ν. Additionally, substituting one equation into another helps to solve when we only have...

Truman Chong Dis 3G

I think it depends on how much energy that the photon has. So if the photon transfers enough energy to the electron to equal the energy difference between for example energy level n=1 to n=3, then electrons would be able to jump multiple energy levels. Electrons jump energy levels only when there is...

Truman Chong Dis 3G

I got D as my answer. To find the wavelength of the krypton-86 we must divide 1 meter by the number of wavelengths (1,650,763.73). This gets us approximately 6.0578...x10^-7 meters (605.78nm) per wavelength or the length of one wavelength of krypton-86. Next, we use c = λν to find ν. So we divide th...

Truman Chong Dis 3G

The speed of the ejected electron depends on the kinetic energy created from the excess energy of the photon hitting the electron which depends not on the intensity or amplitude of the photon but rather the frequency of the electron. Intensity is an increase in amplitude because multiple photons of ...

Truman Chong Dis 3G

I try to take notes as I watch the lecture and highlight things that seem to be emphasized during the lecture. Then on my own time I write down important concepts and equations on a review sheet. I use the review sheet as an outline on which I try to use my own words to explain concepts. If there ar...

Truman Chong Dis 3G

How my TA explained it during our discussion session was that intensity is an increase in amplitude because multiple photons of the same frequency is being emitted and if photons acted as a wave, these waves/photons would simply be added together into a larger wave with higher amplitude but the same...

Truman Chong Dis 3G

With organic molecules such as the ones shown in Question 10, the “zig-zag” line refers to bonds between carbon atoms and each vertex including the points at either end of the zig-zag represents a single carbon atom. Since carbon can from 4 bonds, in organic molecules it is assumed that carbon fills...

Truman Chong Dis 3G

The key point in solving dilution/ concentration problems like this one would be figuring out the number of moles of some type of molecule in this case the number of moles of potassium and sulfide. 1. Find the percent composition of K in each compound. We do so by dividing the molar mass of K by the...

Truman Chong Dis 3G

1. You have to find the percent composition of Carbon and Hydrogen in their respective molecule in the products. This is because the moles of Carbon and Hydrogen stay the same during the reaction but not Oxygen as there is an excess. 2. Next, you have to multiply the percent composition of Carbon in...

Truman Chong Dis 3G

The answers to the odd-numbered questions in the textbook can be found in the back of the e-book starting around page C-12.

Truman Chong Dis 3G

Here’s the link to the Lecture 1 Discussion Group 1K:
https://groupme.com/join_group/63080420/KJo5vqaV

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