CHEMISTRY COMMUNITY

Karina Jiayu Xu 4E

u guys reply with different answers. did lavelle ever post the solution? where can i find the solution?

Karina Jiayu Xu 4E

so is it okay to assume infinite concentration of initial reactants?

Karina Jiayu Xu 4E

i am also confused about this... what do the different orders actually mean?

Karina Jiayu Xu 4E

wait have we already gone over the ochem topics?

Karina Jiayu Xu 4E

to answer your question, yes

Karina Jiayu Xu 4E

It appeared on the 2019 test so I advise future students to learn it well beforehand.

Karina Jiayu Xu 4E

:') i really hope it will be

Karina Jiayu Xu 4E

Calculate using two separate formulas given in lecture then compare the entropy changes

Karina Jiayu Xu 4E

This is so helpful. Are the attachments basically study guides?

Karina Jiayu Xu 4E

Although reading the text book helps, I think simply completing all homework questions and attending lecture and discussion is sufficient to fully understand the course material, to be honest.

Karina Jiayu Xu 4E

It is allowed because entropy is a state function. A lot of what we are working on are state functions (like enthalpy, gibbs free energy), except for work and heat.

Karina Jiayu Xu 4E

You calculate he entropies of the change in temperature and the change in pressure separately and then add them up, since entropy is a state function.

Karina Jiayu Xu 4E

Recall that the change in entropy of the universe is equal to the sum of the change in entropy of the surrounding and the system. And in a reversible reaction, the total change in entropy in the universe is 0, and thus the change in entropy of the surrounding and the system have to equal.

Karina Jiayu Xu 4E

Doing all of the homework problems (not just the 7, but every one listed) helps me the most. His tests are pretty similar to the homework problems sometimes even easier.

Karina Jiayu Xu 4E

you can ask me for notes :) xuj67497@g.ucla.edu

Karina Jiayu Xu 4E

You can also use an ipad to take notes. Goodnotes 4 or 5 are both really good for note taking and organization.

Karina Jiayu Xu 4E

You should just ignore everything thats not in a gaseous state

Karina Jiayu Xu 4E

from what i learned in LS i think when u break a bond u release energy (so youre right). For example breaking off a phosphate from ATP will result in energy release.

Karina Jiayu Xu 4E

thank you so much!! that was actually very helpful considering how stressful the process is.

Karina Jiayu Xu 4E

On the test I used bar and it was fine

Karina Jiayu Xu 4E

for conversion between concentration and pressure? I'm not really sure.

Karina Jiayu Xu 4E

thanks!

Karina Jiayu Xu 4E

an increase in pressure would shift the reaction towards the side with less moles.

Karina Jiayu Xu 4E

You can also look for any part of the compound that has a strong dipole moment, bc that can usually tell you where an extra hydrogen can go

Karina Jiayu Xu 4E

Because Ka and Kb have inverse relationships since Kw is a constant

Karina Jiayu Xu 4E

wait why does the first part happen?

Karina Jiayu Xu 4E

More reactants yields more products until K reaches its original value again.

Karina Jiayu Xu 4E

K is used for the exact equilibrium state and Q is used for anytime during the reaction. When they are not exactly the same then the current reaction is leaning one direction or the other.

Karina Jiayu Xu 4E

Is heterogenous equilibria just a reaction at equilibrium that involves more than 1 phase?

Karina Jiayu Xu 4E

Me too. I hope it's not on the final.

Karina Jiayu Xu 4E

The "ate" refers to only the anion complex. But the overall charge should always be zero.

Karina Jiayu Xu 4E

I think in class Dr. Lavelle said to just name them in alphabetical order.

Karina Jiayu Xu 4E

Do we have to memorize the polydentates for the final?

Karina Jiayu Xu 4E

I think you can identify amphoteric compounds by just memorizing them. Basic oxides are always bound to metals, and acidic oxides alway bound to non-metals. But amphoteric oxides are usually formed by the elements in or close to the diagonal line of metalloids.

Karina Jiayu Xu 4E

Because the lone pairs are more negative than an atom, it pushes harder on the two bonded atoms, thus making the angle between them less than 109.5.

Karina Jiayu Xu 4E

When the electronegativities of two atoms bonded are very different, the molecule will have dipole moment

Karina Jiayu Xu 4E

Hybridized orbitals only occur for sigma bonds. Pi bonds take place in the leftover P orbitals.

Karina Jiayu Xu 4E

Lone pairs are considered to be more repulsive (more negative) and it pushes on the bound atoms.

Karina Jiayu Xu 4E

So does square planar molecules have AX4E2 and tetrahedral just Ax4?

Karina Jiayu Xu 4E

They are the same thing. They both describe central molecules with two atoms bound and one pair of lone pair electrons.

Karina Jiayu Xu 4E

Wait how do you know if there will be resonance structures on a molecule?

Karina Jiayu Xu 4E

Basically molecules with atoms that differ largely in terms of electronegativity should have dipole moments

Karina Jiayu Xu 4E

I might be wrong but I think Dr. Lavelle said that the molecule is the most stable when the FC is equal to 0

Karina Jiayu Xu 4E

I got credit by saying that atoms have discrete energy levels. I hope that helps

Karina Jiayu Xu 4E

Is there a face book group chat?

Karina Jiayu Xu 4E

If a covalently bonded molecule is symmetrical it is polar.

Karina Jiayu Xu 4E

Is the work function the same as the threshold energy?

Karina Jiayu Xu 4E

Does anyone know if Test 2 will be curved?

Karina Jiayu Xu 4E

Can someone explain what a work function is? I think i got that wrong on the test because i thought a work function was work as a function of time.

Karina Jiayu Xu 4E

Is there a reason why they use pie?

Karina Jiayu Xu 4E

I think it’s just where you’ll never find electrons

Karina Jiayu Xu 4E

Can someone explain the relationship between energy level (n) and energy?
I think they’re inversely related but I’m not sure how it works conceptually..

Karina Jiayu Xu 4E

Anton said to always write all the steps out so if your final answer is incorrect, he can still trace back and give you partial points.

Karina Jiayu Xu 4E

Does anyone know what order to put the elements in when writing an empirical formula?

Karina Jiayu Xu 4E

Do you use the least number of significant digits from the given values for your answer?

Karina Jiayu Xu 4E

I took regular chemistry in my sophomore year and here I am three years later taking 14A. I've been watching crash course videos, and that has helped a ton.

Karina Jiayu Xu 4E

1.001 would have 4 significant figures. As the last post says, it depends on whether there's a decimal or not. For example, 100 has only 1 significant figure, but 100. has 3.

Karina Jiayu Xu 4E

Asheley thank you so much!
I was wondering when pre-med students should start studying for the MCAT? Also, what kind of chemistry is on the test?

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