CHEMISTRY COMMUNITY

Joel Meza 3I

I'm sure you're right. I haven't watched the review lecture yet, but the image you provided asks "What is wrong with this cell diagram?" so that should be a mistake that we are expected to recognize, along with the mistake pointed out by Sameer above my post.

Joel Meza 3I

You should look at the units you use in your question/problem. Just make sure that if they initially give you values in hours and the final answer requires the units to be in seconds, that you do the hours to seconds conversion or vice versa if they ask the other way around.

Joel Meza 3I

The slow step doesn't occur as fast as the other elementary steps. Thus, the rate of the reaction as a whole essentially depends on the rate of this slow step. The step before the slow step will be considered in equilibrium because there will be a build-up of products and some of the products will g...

Joel Meza 3I

You need to have made 50 posts by Sunday March 14th while in Chem 14B. Some students will have more because they either posted more than 50 posts this quarter or they had Chem 14A with Lavelle and made posts during that quarter.

Joel Meza 3I

Because I am a biochem major, I had to move from the 14 series onto the 20 series. So instead of taking 14BL, I have to take 20L.

Joel Meza 3I

Cathodes I have seen have always been on the right, and the anode on the left. Everyone else's posts here also suggest the same, so it should be safe to assume this for 14B.

Joel Meza 3I

50 points is the cap for chem community posts, so you can't get extra credit from doing more posts. You get up to 5 points per week and each point is rewarded for every individual post or reply you make, as long as it is in the correct category.

Joel Meza 3I

I look at an "agent" as being something that causes something. So a reducing agent causes reduction, also meaning that the reducing agent was oxidized. An oxidizing agent causes oxidation, which then means that the oxidizing agent was reduced. To determine the oxidizing agent, look for the...

Joel Meza 3I

This event was really cool, especially that it was planned out by fellow classmates and supported by our professor and TAs. Hopefully, this becomes an annual tradition for Lavelle's 14 series courses, I'm sure future students would find as much fun as we did.

Joel Meza 3I

I think the best way to deal with burnout is to go outside. Being locked up at home doing work or spending hours at your computer isn't good for your mental. I would suggest going out for a drive, some exercise (even if you just take a walk), or go get some food or a treat. Listening to music helps ...

Joel Meza 3I

E naught is the value of E at standard conditions: 1 atm, 25 degrees celsius, and 1 M.

Joel Meza 3I

Your equation for E naught should be -(-74.0 x 10^3 J) / (3 mol)(96485 C/mol). This comes from the formula E naught = -(delta G naught) / nF.

Joel Meza 3I

At standard conditions, the concentrations are equal and thus E naught would be equal to 0.

Joel Meza 3I

According to my solution on Sapling, it states that, "Because lnQ and n both double, the effect cancels out in the Nernst equation, meaning E remains constant."

Joel Meza 3I

Why do chemists like working with ammonia?
Because it's pretty basic stuff.

Joel Meza 3I

Delta G is the change in Gibbs free energy at any conditions, while delta G naught is the change in Gibbs free energy change at standard conditions (e.g. 298K and 1 atm).

Joel Meza 3I

In the most simplest terms, when delta G is negative then the reaction is spontaneous and favorable in the forward direction. If delta G is positive, then the reaction is nonspontaneous and favorable in the reverse direction. You can use equations such as " delta G = delta H - T(delta S) "...

Joel Meza 3I

I still need one more midterm this Monday and I'm finally done with grinding out my study sessions. Good luck to those who are reading this and have another exam(s) to go!

Joel Meza 3I

As a biochem major, I have to make the switch over to the 20 series after taking 14B and I was wondering if anyone had taken 20L before or is taking it this quarter. How is the workload, or do you have any tips for me as I take the course this spring?

Joel Meza 3I

I think you need 90% for an A- and so forth like what we were used to in high school, but instead of the minimum for a C- being something like 70%, it's 50% for this class. Lavelle never really explained grades, except for that a 50% gives a C-.

Joel Meza 3I

When delta G is + then the reverse reaction will be favored (favor more reactants). When delta G is - then the forward reaction will be favored (favor more products).

Joel Meza 3I

I've seen questions have the final units required to be in both kilojoules or in joules. The conversion between the two is really easy to remember, so it shouldn't matter which one you choose to use as long as the question doesn't specify. Just remember to pay attention to your units so that you alw...

Joel Meza 3I

The "naught sign" a.k.a. "⁰" just refers to the unit being in standard conditions (which are 298K and 1 atm). If it doesn't give the naught sign, then the unit may still be in standard conditions but you have to figure out if it is, or it is in other conditions.

Joel Meza 3I

Extremely positive chem community post! Thanks for sharing this vibe with everyone in the class.

Joel Meza 3I

I'm going to be enrolling in my 3rd quarter for my Cluster 70 course, LS7B, Math 32A, and most likely Chem 14C!

Joel Meza 3I

I think we should try to get Lavelle to drop his Chem 14 Series Playlist. Would make for some decent background music while I fry my brain studying.

Joel Meza 3I

I just always count the number of posts I make within the week that is going to be graded. I don't really look at the total number of posts because I sometimes post more than 5 times a week by accident.

Joel Meza 3I

I usually draw out the Lewis structures like Lavelle did during the lecture. I think we are already supposed to know how to draw them because that was 14A content. Once I draw the structures of the reactants and products, I am able to tell which bonds were broken and/or formed.

Joel Meza 3I

A phase change is a change in the state of matter where the different states are solid, liquid and gas. So a phase change is a change from one of the states I mentioned to another state.

Joel Meza 3I

When water is boiled, the hydrogen bonds between the water molecules are broken. These bonds are the strongest IMFs, so that's why it takes a large amount of heat to break them.

Joel Meza 3I

Yes, they are the same, they both refer to something in the gaseous state.

Joel Meza 3I

After you install it, you can run it to see how it works. It's pretty easy, and just removes access to your browser and other applications like Siri if you're on Mac.

Joel Meza 3I

As you go from a state of lower energy to higher energy (like solid --> liquid --> gas) it requires energy and is endothermic. As you go from a state of higher to lower energy (like gas --> liquid ---> solid) it releases energy and is exothermic.

Joel Meza 3I

I don't really listen to music while studying because noise distracts me, but I always make sure to listen to music throughout the day outside of school. I listen to R&B (ex: Brent Faiyaz, The Weeknd) or usually rap (ex: Young Thug, Travis Scott).

Joel Meza 3I

Regardless of how we feel, we can't go back and change our test. We have to continue the grind for the next midterm. You guys got this, good luck!

Joel Meza 3I

When you have a reaction A+B-->C and have its K value and then reverse the reaction to C-->A+B, the K value of this reverse reaction will be the inverse of the first K value.

Joel Meza 3I

You use the inverse of the K value when you want to find the K value of the reverse reaction. So if you are given K for A+B-->C and you want the K for C-->A+B then you take the inverse of the first K.

Joel Meza 3I

Whether we will take the midterm in a large lecture zoom call or a discussion zoom call, I think it will work like our final in 14A where our TA invites all of their students into one zoom call and are split into two groups where 2 proctors look over one of the groups respectively.

Joel Meza 3I

I highly recommend attending the various review sessions (UA, review, etc) and also working on the textbook problems as those were the most similar to the questions we had on the exams in 14A.

Joel Meza 3I

The midterm shouldn't be too long. I remember having a good amount of time to revise my answers for both midterm 1 and 2. However, I can't say the same for the final. You shouldn't expect more than 20 questions, I would guess around the 10-20 question range, but more towards the lower end of that if...

Joel Meza 3I

Kc is used when you are dealing with a question about concentrations or molarity. Kp is used when you are dealing with partial pressures.

Joel Meza 3I

Using your numbers, I got the equation 383x^2 +x -0.0320 = 0. Then using the quadratic formula, I get two values (a negative and positive value) where the positive value equals 0.00792789. Maybe you made an error when you wrote out your quadratic equation? I would double-check your math to see if yo...

Joel Meza 3I

The concentration of NO will decrease by 2x and the concentrations for both N2 and O2 will increase by x.

Joel Meza 3I

When choosing the sign of the x value in an ICE box, you have to look at whether the concentration of the products and reactants are decreasing or increasing. You can usually tell which situation it is when you get information on the question such as "participant X has an initial concentration ...

Joel Meza 3I

Yes. When you increase the moles in an equilibrium equation, the moles of every reactant/product increase as well. So if you double the moles of one participant, you also have to double the moles of every other participant.

Joel Meza 3I

Q is the ratio of products to reactants during any time in a reaction, so I would say to use Q when you are unsure. But I would think that a question in this course would give you the K value so you wouldn't have to be unsure. If you're in a lab environment and don't have a known K value, then you c...

Joel Meza 3I

Solids and liquids are omitted, so only H2O as a gas should be included.

Joel Meza 3I

The reactant(s), or molecule(s) being consumed, will have a negative x value. While the product(s), or molecule(s) being formed will have a positive x value. You just have to look at what molecule(s) are being consumed or produced to decide if they have an addition or subtraction.

Joel Meza 3I

Yes, that's correct, Q is just the ratio at any time during the reaction and K (equilibrium constant) is the ratio when the reaction is at equilibrium.

Joel Meza 3I

I don't think we'll be covering this in 14B.

Joel Meza 3I

Compared to both midterms, where I had plenty of time to go over my answers twice, the final really had me struggling to stay within the "3 minutes per question" time frame. I ran out of time and had to guess the answers I couldn't spend time on. I should have probably gone through all the...

Joel Meza 3I

The 50% refers to the amount of points that we can acquire in the class. The class is out of 500 pts so 250 pts would be needed to pass.

Joel Meza 3I

You can find your grade on CCLE, but I would check Saturday when the grade for our final is posted.

Joel Meza 3I

I've heard that it is based on class average once final scores are complete and listed.

Joel Meza 3I

I had my math course evaluation required for 1% of my final grade, but it doesn't seem like this course requires it.

Joel Meza 3I

I will definitely go over the previous outlines to see which textbook problems to go over because Lavelle mentioned that the Final's questions will be based off of them. I also plan to attend review sessions from the TAs and UAs, and especially the ones that Lavelle is hosting.

Joel Meza 3I

There would be 2 pi bonds in CH3CN between the C atom and N atom because there would be a triple bond. All bonds contain one sigma bond while double and triple bonds have additional pi bonds.

Joel Meza 3I

This picture does a pretty good job at showing how a pi bond would break.

Joel Meza 3I

Thank you, I'll add this to my review plan!

Joel Meza 3I

CCLE is up again but there are still some issues with the site as in functionality.

Joel Meza 3I

Try talking to your TA to set up an appointment to go over your own exam if you can't have a general discussion of it because of time in your discussion class.

Joel Meza 3I

Happy late thanksgiving, my family makes tamales this time of year for the holidays.

Joel Meza 3I

Is there no prerequisite for 20L that is a 20 series class? Or in other words, we don't have to previously taken a specific 20 series class to enroll in 20L? Nope! 14A, 20A, and 20AH can each fulfill the prerequisite, and 14B, 20B, and 20BH can fulfill the corequisite. Ah okay, thank you for the cl...

Joel Meza 3I

Yeah, he meant tetrahedral instead of octahedral.

Joel Meza 3I

Yes, it is equal to the total number of bonds. A single bond gives one, double bond gives two, and a triple bond gives 3.

Joel Meza 3I

I think sticking close with purple is a safer bet.

Joel Meza 3I

I believe that question would be asking about intramolecular forces because you are comparing the bonds within two separate molecules (meaning atom with atom in each molecule).

Joel Meza 3I

I hope he does give back points, but maybe that would make us feel a little too comfortable.

Joel Meza 3I

Is there no prerequisite for 20L that is a 20 series class? Or in other words, we don't have to previously taken a specific 20 series class to enroll in 20L?

Joel Meza 3I

You're only ever allowed a non-marked version of the periodic table on Lavelle's website. Just make sure you know the trends by memory for all of his exams.

Joel Meza 3I

As long as you have 12 units you're good!

Joel Meza 3I

005162520 wrote:Does bond length also affect how strong the bond is?

Yes, the larger a bond length the further two atoms are and the weaker than bond is.

Joel Meza 3I

It is actually S that has a larger atomic radius than O. You might have confused the trend for atomic radii on the period table.

Joel Meza 3I

Yes it is a mistake, it should be SO2.

Joel Meza 3I

We are expected to know/memorize the chart because it's not going to be given.

Joel Meza 3I

Call out green, why would they extend their arm?

Joel Meza 3I

I would recommend taking consistent rest breaks to relax your eyes off of your computer screen. We are required to now spend hours looking at a computer screen which fatigues our sight and mind. Definitely use your breaks to do something where you don't look at any screens. I usually take a nap sinc...

Joel Meza 3I

As you go up a group and also across a period to the right on the periodic table, the electronegativity increases. Now, if you go down a group and towards the left on the periodic table, the size of the atom increases.

Joel Meza 3I

If you are talking about the charge of the molecule represented by the Lewis structure, then the charge (along with its number) will go outside of the structure's brackets.

Joel Meza 3I

I do not think that we will be reviewing the midterm as we need to move on and prepare for midterm 2. If you have some questions, the drop in sessions should be a good way to get some understanding.

Joel Meza 3I

I would go help shut off the reactor.

Joel Meza 3I

I think mnemonics are great for remembering, but I just have memorized them by remembering a color coordinated periodic table. Maybe try looking at one a couple times a day or using one when you work on problems that require you to refer to the periodic table, so that you get that image in your head...

Joel Meza 3I

I've heard that grading has been delayed for whatever reason, although I'm not sure if that is really the case. So I would assume that we might have to wait a week or two before we receive our scores.

Joel Meza 3I

Wavelength cannot be negative, but you might calculate energy to be negative. This would just mean that energy was released in that chemical process described in the question.

Joel Meza 3I

Black body radiation isn't something that we go into depth for this course. So it will not be in any midterms or the final.

Joel Meza 3I

Also, make sure to create posts that are related to the topic you are posting under. Any posts should be valid as long as you are contributing in some way.

Joel Meza 3I

A photon is emitted as an electron goes down one energy level. Once it is at the ground state, a photon cannot be emitted as there is no energy level below the ground state.

Joel Meza 3I

If I remember correctly, Lavelle mentioned that either unit is fine for a general answer. However, if a question asks for something concerning a wavelength, it is best to convert the units to nanometers (nm) as wavelength is given in that unit.

Joel Meza 3I

We use h/4pi because writing out the actual value of this constant wouldn't be convenient. It is much easier to write this out as h/4pi and then plug in the values into the calculator when it comes time to do so in the question.

Joel Meza 3I

That number is the mass of an electron, it's just a given and it is listed on the "Constants and Equations" handout Lavelle provided for us to use during our midterms and final in case you don't memorize it along the incoming weeks.

Joel Meza 3I

An increase in intensity does not relate to an increase in energy of a photon. Intensity only relates to the number of photons, not the energy each photon has. It is the frequency of a photon that determines its energy.

Joel Meza 3I

If you are still waiting to receive an access code in the mail after purchasing the e-textbook with Sapling through the UCLA store, try calling or e-mailing to see if you can receive your code digitally rather than having to wait.

Joel Meza 3I

I am not sure if there is a GroupMe for that specific discussion, but you can ask around about it in the main GroupMe or you can create one with your discussion peers next time you meet them in your weekly discussion zoom call.

Joel Meza 3I

You shouldn't worry too much. A lot of us are also rusty on our chemistry as some of us haven't taken it since our sophomore year in high school. If you ever are in need of any help, you may use Chemistry Community, the step-up sessions, or any of the discussion zoom calls that Lavelle hosts (there ...

Joel Meza 3I

On the home page of this course on Sapling, the e-textbook should be located on the very right side of the page under the Clock. It will then open up a new page (where I think you might need to sign in if it is your first time accessing the e-textbook) and you should be good to go.

Joel Meza 3I

I believe that if you're balancing an equation that is already given to you, the states of the molecules should already be given to you too. If they are not, I do not believe that it is necessary to go and find out what state of matter they are in. For knowing which state of matter each molecule is...

Joel Meza 3I

If the states of matter are given to you in an unbalanced chemical reaction, definitely include them when you balance. However, if the states of matter are not given to you initially, I don't believe it is necessary, at this level, to search the states of matter to include in the balanced chemical r...

Joel Meza 3I

I believe that if you're balancing an equation that is already given to you, the states of the molecules should already be given to you too. If they are not, I do not believe that it is necessary to go and find out what state of matter they are in. For knowing which state of matter each molecule is ...

Joel Meza 3I

No, stoichiometric coefficients do not have units. They just indicated a number that is related to the number of moles of the compound it represents.

Joel Meza 3I

I don't believe there is a correct way to balance chemical reactions, but I find it effective to first balance the element that has the most bonds, which is typically carbon. I hope somewhat helps you out.

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