CHEMISTRY COMMUNITY

Adam Bustamante 1I

when you do the half reactions, the number of electrons transferred would be your number of moles for n

Adam Bustamante 1I

delta E would be 0 when at equilibrium.

Adam Bustamante 1I

the final will most likely have a distribution of problems according to how much time we spent on each outline.

Adam Bustamante 1I

the first step determines how fast the reaction is because it is the slowest step and the reaction cannot go slower than the slowest step.

Adam Bustamante 1I

I'm a philosophy major but am also premed. I really loved bio (though I didn't take it here at ucla) and the psychology and sociology classes required but I'm just not good at chemistry. premed is a lot of work but I like to think it'll pay off in the end, no matter what route we end up taking. like...

Adam Bustamante 1I

the salt bridge's purpose is to maintain a balance of the charges (negative and positive).

Adam Bustamante 1I

I think it was said in lecture that there's no way to immediately tell what order of reaction is just from looking at it and that you'd need the rate constant and the concentrations.

Adam Bustamante 1I

molecularity is the number of species in an elementary step; so if the step was A + B --> P, it would be bimolecular because of the two species, and it would have rate law of k[A][B].

Adam Bustamante 1I

I personally watch the organic chemistry tutor's "new general and ap chem" playlist to help me review for the topics in this class.

Adam Bustamante 1I

temperature is the only thing that can cause k to change.

Adam Bustamante 1I

the oxidizing agent is reduced, whereas the reducing agent is oxidized.

Adam Bustamante 1I

I would end the tab and log back into CCLE then go back to sapling to see if it has updated. usually that will help fix the error.

Adam Bustamante 1I

there's one problem in this week's homework that says that states of matter should be included, so if you're sure it's balanced correctly try putting the states of matter in the equation.

Adam Bustamante 1I

You have to take off the parentheses in the products side; I was stuck wondering why it wouldn't accept my response too!

Adam Bustamante 1I

a shorter reaction is controlled by kinetics whereas thermodynamics control longer reactions, such as

Adam Bustamante 1I

cell potential is not a state function because the pathway it takes matters.

Adam Bustamante 1I

coefficients do not affect the oxidation numbers; they're just there to help balance the chemical equation.

Adam Bustamante 1I

when I took biology at my first college we learned OILRIG too when discussing redox!! really helpful

Adam Bustamante 1I

I would say that it really depends on the units you're given in the problem; the value of 0.08206 has units (L)(atm) / (mol)(K), whereas the 8.314 has units J / (mol)(K).

Adam Bustamante 1I

When Q is less than K, the reaction will be in the forward direction (favoring the products). If Q is larger than K, the reaction will be in the reverse direction, favoring the reactants.

Adam Bustamante 1I

Hi! You would multiply the partial pressures if there's more than one in either the numerator or denominator.

Adam Bustamante 1I

I don't think the equation is on the equation sheet, but I think we should definitely memorize it just in case it makes an appearance on the test.

Adam Bustamante 1I

I believe that the states have to match when using Hess' Law and cancelling them out because they have to be the same coefficient and phase for them to truly cancel each other out.

Adam Bustamante 1I

Yes, because since both enthalpy and entropy are state functions, the same rules apply.

Adam Bustamante 1I

Chemistry community posts points aren't updated weekly, they're updated more so every few weeks, so I wouldn't stress out too much if yours isn't accurate at the moment. I have a 20/25 but I still did my week 5 posts, they're just not graded yet :)

Adam Bustamante 1I

Gibbs free energy would determine spontaneity because it measures the conditions under constant temperature and pressure.

Adam Bustamante 1I

Entropy is the amount of disorder in a system, delta S.

Adam Bustamante 1I

The two gas constant values (that I know of) are 8.314 J/(mol x K) and 0.08206 (L x atm)/(mol x K) and I think it just depends on what units the problem is asking the answer to be in, along with what units the problem gives to you. Both are on the equation sheet we're allowed to use during the midte...

Adam Bustamante 1I

Kc and Kp are solved the same way! Kc is for concentration whereas Kp is for pressure, but both can be solved for using the setup: [products]/[reactants].

Adam Bustamante 1I

I'm thinking of taking both Chem 14 BL and Chem 14C together next quarter, along with another class for my major. I think you should consider both if you have time allotted for a lot of studying and busy work.

Adam Bustamante 1I

Just the stuff covered in week 3 from outline 3 will be on the midterm. outlines 1 and 2 are both fully covered so expect to be tested on any of that too.

Adam Bustamante 1I

you just click on the link with respondus in it and it'll prompt you to close other applications that are currently open and then it'll open the respondus window so you can take the test.

Adam Bustamante 1I

I've read that there are specialized printers that undergo sublimation as well as mothballs and solid air fresheners.

Adam Bustamante 1I

q is for the heat whereas H is for enthalpy.

Adam Bustamante 1I

On Monday's (1/25) lecture, where did Dr. Lavelle get the value of 6.9^C in the final problem of the lecture video/ I know the problem stated that T=31.9^C but where did we get a second value to get the change in temperature to be at 6.9?

Adam Bustamante 1I

To get the percent ionization you need to use the quadratic equation in this problem. I converted the Ka to a full decimal rather than the x10^-4 so I'd be working with just decimals and solved for x using the quadratic equation. Then you'd want to solve for ionization by doing x/(initial concentrat...

Adam Bustamante 1I

Ka is the acidity constant and Kb is the basicity constant. Usually the problem would tell you which one you're solving for, and you'd solve them using [P]/[R].

Adam Bustamante 1I

I think it would be [H3O+]/[HA]

Adam Bustamante 1I

I would recommend studying the assigned problems from the book for each section, as some of them make their way onto the midterms. Going over the lecture notes is a good way to review concepts. I also recommend the organic chemistry tutor on youtube, he's great at explaining things!

Adam Bustamante 1I

Autoprotolysis is a molecule transfers a proton to a similar molecule, like in H2O. A proton is transfer to another H2O and becomes H3O+, making the one that transferred the proton OH-.

Adam Bustamante 1I

P= pressure
V=volume
n= moles
R= gas constant
T= temperature in Kelvin

Adam Bustamante 1I

I think we'd be asked to give it in either bar or atm, but in one of the lecture videos he said that 1 bar is approximately 1 atm, so I guess its just up to whether the problem is asking for bar or atm in units.

Adam Bustamante 1I

water can be either an acid or a base and is considered weak because it does not completely ionize.

Adam Bustamante 1I

R is a constant, which would either be given to us on the equation sheet, or we'd have to know it. R= 8.3145

Adam Bustamante 1I

pKa refers to -log[H3O+][conjugate base]/[acid] whereas pH refers to -log[H3O+]

Adam Bustamante 1I

K is an equilibrium constant, but Kc is understood as an equilibrium of concentration constant, so they're basically the same. K is just a broader term.

Adam Bustamante 1I

In a reverse reaction, K would become inverse, so it would be 1/K.

Adam Bustamante 1I

I would leave the temperature in Kelvin for its units because that is the correct unit when using ideal gas laws.

Adam Bustamante 1I

One of the audio visual modules said that for now we're just going to convert 1 bar = 1 atm.

Adam Bustamante 1I

When working with the ideal gas laws we would use Kelvin as our unit for temperature.

Adam Bustamante 1I

if the arrows of the dipole moments can cancel each other out then the molecule will have no net dipole moment.

Adam Bustamante 1I

the 2H2O is called dihydrate because it is not within the brackets. If it was in the brackets, however, it would be diaqua.

Adam Bustamante 1I

Thank you so much for sharing this! definitely will be helpful when I study

Adam Bustamante 1I

cisplatin is the chemotherapy drug mentioned in lecture. it binds to the DNA and the two adjacent guanines.

Adam Bustamante 1I

I think only some of the textbook questions will appear on the final

Adam Bustamante 1I

For hybridization, just count the amount of regions of electron density. 1 region would be s, 2 regions would be sp, etc. There are really helpful charts you can look up and study if you're still unsure, but other than that, it's pretty straightforward :)

Adam Bustamante 1I

You have to take into consideration the amount of lone pairs on the structure, as they can modify the shape and push down on the other bonds, lessening the bond angles.It doesn't matter if the lewis structure is all the same element, it's all about lone pairs and regions of electron density.

Adam Bustamante 1I

Hemoglobin transports oxygen to the blood and has 4 myoglobins. Myoglobin delivers oxygen to the muscles in the body.

Adam Bustamante 1I

I don't think it matters which way you write it (H2O or OH2) but I think you would use one over the other depending on where the molecule is bonding.

Adam Bustamante 1I

I believe that the content distribution on the final will be relative to how much time we've spent going over each unit so like the quantum world unit would have more question than naming coordination compounds, for example. To be safe though, I would say just study everything.

Adam Bustamante 1I

To be safe, I would just try to memorize the different VSEPR shapes and bond angles. We might not need to know every single one of them exactly but maybe just be tested on certain aspects about them, but who knows.

Adam Bustamante 1I

A delocalized pi bond would mean that the Lewis structure has resonance

Adam Bustamante 1I

PO4 ^3- has four regions of electron density. Even though it has a double bond, it still counts as just one region (single, double, triple bonds = 1 region). The hybridization for P would then be sp3.

Adam Bustamante 1I

The axial atoms are in the same plane as the central atom and are 180 degrees apart from each other while the rest of the atoms are equatorial atoms.

Adam Bustamante 1I

A single bond has 1 sigma bond; double bonds have 1 sigma bond and 1 pi bond; and triple bonds have 1 sigma bond plus 2 pi bonds.

Adam Bustamante 1I

NO2- has a bent shape because of the lone pair of electrons. Lone pairs create electron repulsion, pushing down, causing the molecule to have a bent shape rather than linear.

Adam Bustamante 1I

If the molecule's shape is symmetrical, it is polar whereas if the molecule is asymmetrical, it'll be non polar.

Adam Bustamante 1I

Yes, lone pairs of electrons count as regions of electron density!

Adam Bustamante 1I

A dipole-dipole force occurs between an atom that has a partial positive charge and another atom that has a partial negative charge. the electrons are being pulled towards the more negative atom, which indicates the direction in which we draw the dipole arrow. An induced-dipole is when a dipole exer...

Adam Bustamante 1I

You're correct, the shape name is bent! It could also be angular, but bent is perfectly acceptable :)

Adam Bustamante 1I

I don't think the direction matters when writing the arrows, but if you start with a spin down arrow and are filling the other shells with Ione arrow each, then you'd want to continue with the spin down arrows.

Adam Bustamante 1I

Midterm 2 is everything since Midterm 1, ending with material in 11/11's lecture.

Adam Bustamante 1I

In Dr. Lavelle's lecture, he said that high polarizability is related to high attractiveness. In the tube and rod example, the tube on the left had fewer electrons, making it less polarizable whereas the tube on the right had the most electrons out of the three, making it the most polarizable and at...

Adam Bustamante 1I

Usually when a problem is asking you which Lewis structure is the most stable, you'd want to use formal charges.

Adam Bustamante 1I

Thank you so much for this! I know that when I was doing Sapling there was part of a question asking about oxidation numbers which kind of threw me off, but now I can go back and try it out

Adam Bustamante 1I

p stands for momentum and can be written as mv, where m is the mass and v is the velocity

Adam Bustamante 1I

You can use either equation to find the energy of a photon, but I like to use E=hv because it's easier for me to plug things in and solve for. If you're given a frequency or wavelength you could use that one, but if you have key words like "how much energy is required to eject.." it'd remi...

Adam Bustamante 1I

Paired electrons means that one will be spin up and the other spin down whereas a parallel spin means there's only one electron in each shell with both spin up.

Adam Bustamante 1I

I've attended a few step up sessions and workshops before the first midterm and found them to be really helpful. I'm not the greatest at chemistry but the hosts usually explain in detail about how and why we do something in a problem and at the end of the session I feel more confident. The textbook ...

Adam Bustamante 1I

Midterm scores will be available Thursday 11/5!

Adam Bustamante 1I

I think the second midterm will cover material we learn after midterm 1, starting with quantum numbers and electron configurations up until wherever we stop.

Adam Bustamante 1I

I would always make sure to first convert nm or pm to m, in order to stay consistent with the units used in the uncertainty equation (m/s) when solving for velocity. Unless specified otherwise, convert to m.

Adam Bustamante 1I

for m you would use the mass of the electron because it has the key word electron in the question and because m is part of the equation solving for the energy. the mass of an electron is equal to 9.11x10^-31 kg.

Adam Bustamante 1I

From all the material we've covered, c is always going to be a constant (the speed of light), 2.998x10^8 m/s. In the future maybe there will be another variable, c, that could also be another constant, but until now, just know that its the speed of light!

Adam Bustamante 1I

The midterm is taken during our discussion sections and is proctored by our TA. It's multiple choice with 12 questions and I believe partial credit for some questions. Quantum numbers aren't on it.

Adam Bustamante 1I

Dr. Lavelle has a sheet of equations and a periodic table on his website that we should print out in order to be ready for the exam.

Adam Bustamante 1I

Anything with a wavelength of less than 10^-15 does not have detectable wavelike properties.

Adam Bustamante 1I

So, electromagnetic energy is measured in units of photons. Wavelength and frequency are set properties of the pulse of light, and energy is proportional to the number of photons. So because the question is asking for the energy of 100 photons, the answer would be energy, E, is 100, along with just ...

Adam Bustamante 1I

Planck’s constant is 6.626x10^-34 J.s and typically assumes the variable h.

Adam Bustamante 1I

Hey there, What I do is everyday I do a section of the assigned, though not graded, homework problems from the ebook and then review them when completed. I had seen on the course syllabus that were encouraged to do those problems because some may appear on the midterms, so I’d definitely suggest att...

Adam Bustamante 1I

In problems asking you to determine the empirical and molecular formulas, the problem will state the molar mass of the molecular formula. This indicates that you need to find the empirical formula and then the empirical formula's molar mass in order to proceed. Then you'd divide (molecular/empirical...

Adam Bustamante 1I

During my calculations I write down whatever the periodic table has for molar masses and don't round until I get to my final answer (this prevents any errors or wrong number of significant figures). Then, I just look at the problem and find the lowest number of sig figs used and round the final answ...

Adam Bustamante 1I

Hey! I've been using the 2020 iPad Pro and the apple pencil to take notes with and to organize all my subjects by folder and so on. I think it's super worth the money because you're able to condense say, 5 notebooks, into the notes app! it's also really convenient having access to a bunch of differe...

Adam Bustamante 1I

I think Dr. Lavelle prefers having all stoichiometric coefficients as whole numbers rather than fractions. You can just multiply the entire balanced equation's coefficients by the fraction's denominator to achieve the whole numbers.

Adam Bustamante 1I

I've been told to go in order from least occurring to most occurring in the chemical equation while balancing. Also, writing each element/compound underneath both sides (reactants and products) help me keep track of where I am in balancing because you can just start crossing them out and seeing if t...

Adam Bustamante 1I

Hi there,

I believe that we are going to be given a periodic table along with a formula sheet with helpful formulas and constants that are allowed to be of aid on the exams this quarter.

Adam Bustamante 1I

Does anyone know how to do L5 from the fundamentals section of the book problems? The solid fuel in the booster stage of the space shuttle is a mixture of ammonium perchlorate and aluminum powder. Upon ignition, the reaction that takes place is 6NH4 ClO4 (s) + 10 Al (s) → 5 Al2O3 (s) + 3N2 (g) + 6HC...

Adam Bustamante 1I

The Organic Chemistry Tutor on YouTube is super helpful when it comes to literally any topic in STEM subjects. He has a playlist dedicated to different subjects and they've been super helpful so far

Adam Bustamante 1I

I think we could be tested on finding any of the variables, be it M1, V1, M2, or V2. Just as long as we have enough given information and know how to manipulate the equation to isolate and find the variable that's asked, we should be fine.

Adam Bustamante 1I

g.mol^-1 and g/mol are interchangeable so you can use whichever you prefer!

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