CHEMISTRY COMMUNITY

Madison Muggeo 3H

I'm planning on doing since I'll be vaccinated by then (I'm a grocery store worker) but I will be trying to stay as safe as possible.

Madison Muggeo 3H

Hi! In a workshop, the UA said that in general that if there is a liquid, odds are it is the solvent and is not included, but it really depends on the equations that you are given. Hope this helps!

Madison Muggeo 3H

Hi! The slowest step is the rate-determining step. The easiest way to think about this is if it takes you an hour to shower but only 2 minutes to get dressed, the time of your shower will determine how long it will take you to get ready overall. Hope this helps!

Madison Muggeo 3H

Organic Chemistry Tutor and Khan Academy is the way to go!

Madison Muggeo 3H

Honestly, I've been better and I'm just looking forward to break because we all need one. Hoping to finish out this quarter strong!

Madison Muggeo 3H

Lavelle said that for this class we will not have to know the equations for them, as they are not as common as 0/1/2 order reactions.

Madison Muggeo 3H

Hi! .639 is just ln(2) which you get as your numerator when you rearrange the integrated rate law and plug in the values for when t=t1/2. Hope this helps!

Madison Muggeo 3H

Hi! I think Lavelle mentioned that 0 order reactions weren't uncommon, but not as prevalent as 1st/2nd. It basically means that a change in the concentration will not affect the rate of the reaction. Hope this helps!

Madison Muggeo 3H

Hi! Basically, the order will tell you how much the concentration of that reactant will affect the rate of the reaction. Hope this helps!

Madison Muggeo 3H

I was in a UA session, and they said that for some questions it'll ask for the mean, so you just the average. I do not believe that this has to be done for all questions.

Madison Muggeo 3H

I might be in the minority here, but I liked thermodynamics. idk why it just clicked for me!

Madison Muggeo 3H

i always get a bit confused with this but can someone briefly explain what exactly dilution is please? i guess more specifically, what it means to dilute something/what is happening when something is being diluted Usually when you dilute a solution, you add water to it, which decreases the concentr...

Madison Muggeo 3H

Hi! When we balance half-reactions we usually denote the number of e- transferred in moles, for example, +2e- would be 2 moles of electrons. The actual number of electrons transferred is 2*(6.022*10^23). It is way easier to use the molar number instead of the actual amount.

Madison Muggeo 3H

Hi! In acidic solutions, you would use H+ ions to balance the equation but in basic solutions, you would use OH-. Hope this helps!

Madison Muggeo 3H

I think it would be a good idea to memorize the ubiquitous ones, and I would know the exceptions (like O being -1 in peroxides).

Madison Muggeo 3H

Hi! The oxidizing agent is the molecule that is being reduced, and the reducing agent is the molecule that is being oxidized. Hope this helps!

Madison Muggeo 3H

I would say that the phases of the compounds should be taken into account first, so solid<liquid<gas. Entropy also increases with more complex molecules, which is something else to look out for.

Madison Muggeo 3H

Yep! You would be using that equation. In this class, we usually ignore thermal disorder, as that would make our calculations more complicated. Hope this helps!

Madison Muggeo 3H

Thermodynamically favorable is when delta G is negative, and the forward reaction is positive!

Madison Muggeo 3H

Hi! In terms of delta G, a system is spontaneous in the forward direction if delta G is negative and spontaneous in the reverse direction if delta G is positive. Hope this helps!!

Madison Muggeo 3H

Hi! STP is 1atm and 0 degrees C (273.15K). SATP is at 1 atm and 25 degrees C(298.15K). Hope this helps!

Madison Muggeo 3H

If the lid is closed, and the mug is of high enough quality then yes, it is an isolated system.

Madison Muggeo 3H

Hi! I watched all of WandaVision last night, and it is soooo good!

Madison Muggeo 3H

Hi! It honestly depends on what the question gives you, but I would be comfortable using both.

Madison Muggeo 3H

I believe my TA said he would give these values to us in a problem, as they are not listed on our equation sheet :)

Madison Muggeo 3H

Hi Marc, I think that positons are relative to what it is that you are talking about. For example, in the glass bulb design that you mentioned, the number of positions was deliberately chosen by experiment which is why there were only 2 positions in that case. Also, I don't know if you remember, bu...

Madison Muggeo 3H

I believe that it is usually in J/K, but it honestly depends on the problem, if there is a large amount it may give the answer in KJ just because it is easier to write. Just make sure when you are doing calculations that all your terms are in the same unit to avoid calculation errors!

Madison Muggeo 3H

This thread is so cute! My family bakes a lot and I was surprised to see how many chemistry topics that we learned applied to what we were doing in the kitchen. I don't remember who said this in the thread but I agree that cooking/baking is a more fun form of chemistry lol

Madison Muggeo 3H

Hi! It depends on the units that you're trying to cancel. When using the ideal gas law, it is usually .08206L*atm(or bar)/K*mol. When trying to solve for J you would use 8.314 J*/K*mol. Hope that helps! :)

Madison Muggeo 3H

No, a constant volume does not imply constant pressure and vice versa. If you look at the ideal gas law, PV=nRT, you'll see that pressure and volume are inversely related.

Madison Muggeo 3H

When heat is gained by the system q is positive, and when it loses heat it is negative. If the system is doing work, the value of w is negative, but if the system is having work done on it then w is positive.

Madison Muggeo 3H

Hi! It just depends on the signs of q and w, because deltau=q+w (deltau=q if at constant volume). When you calculate these values and add them together, the sign of deltau will either be positive or negative.

Madison Muggeo 3H

Work being done by the system is negative(losing energy to do that work) while work being done on the system is positive(gaining energy to do that work).

Madison Muggeo 3H

Can someone explain why q equaled the change in U in the last few questions. I am confused on why they are the same answer but use different notations. Hi! q=deltaU in the last few sapling questions because the volume was kept constant and when the volume is constant, w=0 (-P*(deltaV=0) or (-P*0). ...

Madison Muggeo 3H

Hi! This is found on our formula sheet, and you just plug the values into the expression, and calculate the answer!

Madison Muggeo 3H

I had a similar question, so thank you to those who answered :)

Madison Muggeo 3H

We don't have to memorize them, they should be given in any problem we have :)

Madison Muggeo 3H

Using the table in the textbook that has the enthalpies of formation for different compounds you will see that some of the values are equal to 0 and those are the standard states for those elements. I just made a list out of those and memorized it hope this helped :)

Madison Muggeo 3H

Hi! For this problem, you would calculate the enthalpy for 6 bonds with resonance vs, 3 double bonds and 3 single bonds between Carbon atoms. When you do this, you see that the enthalpy for the structure with the resonance bonds has a higher value, meaning it is more stable.

Madison Muggeo 3H

Q is just the transfer of heat, while H is the enthalpy of the system.

Madison Muggeo 3H

Hi! When you reverse the equation, you multiply the value by -1. That is why it is -2 instead of +2.

Madison Muggeo 3H

Hi! The catalyst will not change the change in enthalpy for the overall reaction, because enthalpy is a state function. It doesn't matter what path is taken, the value will be the same.

Madison Muggeo 3H

I think it is just something you have to memorize, Lavelle briefly went over it during lecture.

Madison Muggeo 3H

Hi! It refers to what phase the element is at 25 degrees C, and 1atm.

Madison Muggeo 3H

Thank you all for responding :)

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!

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