CHEMISTRY COMMUNITY

Madison Muggeo 3H

We should be given the units in whatever question we have, but 1 bar is roughly equal to 1 atmosphere so we use them interchangeably

Madison Muggeo 3H

The descriptions above are really good, but another description that might help is from one of the UA's. They described the reaction as a balanced scale. When one side dips, the other side rises, and vice versa. The reaction will then move to make sure that the scale is even/level again.

Madison Muggeo 3H

Hi! Usually when you get two positive values, one will be greater than the initial concentration you started with, so this value is not usable and you would ignore it. Hope this helps!

Madison Muggeo 3H

My TA addressed this in our session last week, and I think your explanation is correct! :)

Madison Muggeo 3H

Does anyone know what the calculator policy for this class is? I've been using a graphing calculator and would like to know if they'll be allowed for the exams (midterms and finals).

Madison Muggeo 3H

Hi! In the reverse reaction, it would be 1/K since the fraction is flipped. Hope this helps :)

Madison Muggeo 3H

Hi! The temperature should always be in Kelvin because all gas constants use Kelvin as their unit for temperature so it's just easier. :)

Madison Muggeo 3H

I would say if the reactants or products are in the gaseous phase you can use Kp or Kc (but the question should specify) and if the reactants and products are in the aqueous state (aq) then we would use Kc because you cannot convert the concentration of an aq solution to partial pressure. Hope this ...

Madison Muggeo 3H

I had a similar issue with this question thank you for replying! :)

Madison Muggeo 3H

I think in this class Lavelle said that we will assume that all gases are ideal gases so we can use the equation but this may not be the case in future classes :)

Madison Muggeo 3H

Thank you so much for this!

Madison Muggeo 3H

Thank you and good luck to everyone!!!

Madison Muggeo 3H

I would suggest UA worksheets for older subjects and textbook questions for the most recent.

Madison Muggeo 3H

Melis Kasaba 2F wrote:If you have the pH, you should be able to find [H+], [OH-], and pOH. Here's a helpful chart that tells you what formulas to use:20140811155915521305.png

This is such a helpful graphic thank you!

Madison Muggeo 3H

My TA said it will be similar to the midterms, some will come from textbook problems but not all.

Madison Muggeo 3H

Hi! The bond length between H and F is shorter than the other bonds mentioned, and additionally, F is very electronegative so it is difficult for it to completely dissociate. Strong acids are easily dissociable, due to their longer and weaker bonds and closer electronegativity differences (in this e...

Madison Muggeo 3H

Hi! Someone in the UA session today had a similar question and the UA said to just go by what Lavelle tells us, as he is the one in charge :)

Madison Muggeo 3H

I did the same thing! I spelled ammine 'amine' and could not figure out why the problem kept marking the question incorrect. Glad you figured it out :)

Madison Muggeo 3H

Hi! In this example, the second Cl is not directly bonded to the metal which leaves it outside of the immediate sphere of influence for the metal atom.

Madison Muggeo 3H

Thank you for this! I usually only watch organic chem tutor but I will definitely watch the other ones too :)

Madison Muggeo 3H

Just checking my understanding: bond order refers only to the number of bonds present and not to any actual chronological order or bonds (sounds silly, but that's what I originally inferred from the use of the word order haha). A single bond has a bond order of one, a double bond has a bond order o...

Madison Muggeo 3H

For determining the shape you only take regions of electron density into account even if it is a double bond, it is only one region of electron density so there are three total around the carbon atom.

Madison Muggeo 3H

https://d20ohkaloyme4g.cloudfront.net/i ... 0_1697.png
Is the table that I memorized, it is really useful.

Madison Muggeo 3H

This post was so helpful, I had a similar question. Thank you to all that responded!

Madison Muggeo 3H

Hi! You would read the molecule from left to right, and it will give you the order. Hope this helps!

Madison Muggeo 3H

Hi! The lone pairs on the oxygen repel each other and take up space, "bending" the hydrogen atoms downward. Hope this helps!

Madison Muggeo 3H

Yes the notation will help determine the shape but we still need to know the bond angles because these can differ from molecule to molecule because of the different atoms within them :)

Madison Muggeo 3H

I believe we should know the relationship between bond angles and lone pair electrons on the central atom. We were never taught how to calculate them, so we will not need to know the exact number, just an approximation based on the structure.

Madison Muggeo 3H

This will be bent. I'm not sure how to attach a picture on this website, but there are some really good graphics of the VSEPR table with lots of useful information. Once you memorize these tables, it becomes easier :)

Madison Muggeo 3H

I was about to reply with Organic Chemistry Tutor as well! He's super helpful and is a good resource to utilize when you may not understand a subject.

Madison Muggeo 3H

I start with the octet rule and then use formal charge to check over my work, and if there are any charges that needed to be added I will add them. It is helpful to use both, but you should start with the octet rule. I do this as well to make sure I don't leave out any electrons! However, I was uns...

Madison Muggeo 3H

My TA said that we should know the general trend, but if there is a question that asks for the specific difference in electronegativities, we would be given the values needed.

Madison Muggeo 3H

darchen3G wrote:Single bond: 1 sigma
Double bond: 1 sigma 1 pi
Triple bond: 1 sigma 2 pi
Quadruple bond: 1 sigma 2 pi 1 delta

What exactly is a delta bond? Have we gone over this?

Madison Muggeo 3H

Generally, polarizability increases as the volume occupied by electrons increases. On rows of the periodic table, polarizability decreases from left to right (larger molecules are more polarizable than smaller ones). Polarizability increases down on columns of the periodic table. I hope this helps!...

Madison Muggeo 3H

I start with the octet rule and then use formal charge to check over my work, and if there are any charges that needed to be added I will add them. It is helpful to use both, but you should shart with the octet rule.

Madison Muggeo 3H

Thank you for this! Memorizing these will be a great help for the midterm :)

Madison Muggeo 3H

Coordinate covalent bonds are when one atom donates both electrons to form a bond, such as a Lewis base.

Madison Muggeo 3H

Basically, if a structure can have a double or a triple bond in more than one position on the Lewis Structure, it means that there is resonance. In reality, the structure has a mixture of single or double/triple bond characteristics. This would lead to the bond length being shorter than a single bon...

Madison Muggeo 3H

I had a similar question, so thank you to all that responded!

Madison Muggeo 3H

Someone in the GroupMe mentioned organic chemistry tutor on Youtube? I'm not too familiar with him but others seem to like his videos. Also, I would assume that we do have to memorize these.

Madison Muggeo 3H

Just joined, thank you so much for organizing this!

Madison Muggeo 3H

Random question, could the Rydberg equation be theoretically used for another ion of a different element such as He+1? Or does it have completely different properties than H, and could not be used?

Madison Muggeo 3H

This thread is so useful! I tried this problem so many times, and you guys helped me understand the correct answer! Thanks, everyone!

Madison Muggeo 3H

What do you call a tooth in a glass of water?
~
~
One Molar solution.

Madison Muggeo 3H

I had a hard time understanding this stuff at first, but all these explanations really helped! Thanks guys!

Madison Muggeo 3H

To whoever posted the formula for the number of electrons, thank you! I have never seen that before.

Madison Muggeo 3H

I've also heard that the answer choices will be varied enough that if we round too soon or our SF are off, it will be easy to tell what the answer should be from a UA.

Madison Muggeo 3H

I've heard different things from different people. I've heard anywhere from 10-30 questions which is not helpful, but we're all in the same situation :)

Madison Muggeo 3H

A UA described it as in the change in E=hv, the units for change in E are J/photon. To find the number of photons you divide the total energy by the J/photon and the Joules cancel out and you are left with your answer in # of photons.

Madison Muggeo 3H

I went to a UA session today, and he said he thinks we do not need to know much for this midterm, and just discussed the s and p orbitals and how there are certain areas of a higher probability of finding electrons within them.

Madison Muggeo 3H

I had the same question! Thanks to those clarifying above, I could not figure out what I was doing wrong.

Madison Muggeo 3H

I've found that staying organized and planning out what assignments I'm going to do each day really helps, and you can use a calendar app like google calendar to plan around your lectures. I personally find the UA workshops extremely helpful and I try to go to as many as I can fit in per week becaus...

Madison Muggeo 3H

Thank you to all who replied to help! I really appreciate it.

Madison Muggeo 3H

This thread helped me with one of the problems in a UA workshop, so thank you to all who commented!

Madison Muggeo 3H

Thank you for bringing back the music before the lectures!

Madison Muggeo 3H

Thank you guys for this post! I was confused and the explanation really helped :)

Madison Muggeo 3H

Thank you for this thread! I got stuck on #29 but this really helped!

Madison Muggeo 3H

Hi! Can anyone help me with this question?

Molybdenum metal must absorb radiation with a minimum frequency of 1.09 x 1015 s-1 before it can emit an electron from its surface.
What is the minimum energy needed to produce this effect?

Thanks in advance!

Madison Muggeo 3H

I'm not the OP, but thank you to those who responded because like the OP I tend not to have the neatest work, and this thread helped make me less anxious about exams. Thanks!

Madison Muggeo 3H

I had a similar question! I tend to make mistakes when I round too soon, so I try to keep at least 2 extra SF in my calculations, then I round for my final answer.

Madison Muggeo 3H

Hi!

Similar to all the other comments, I would assume that unless it is stated in the problem we should not guess the states of the reactants and products. However, if it is given in the problem we should include them.

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