CHEMISTRY COMMUNITY

Margia Adriano 2A

Hi! On Sapling Wk9/10 Number 16, an increase in temperature affects the reaction with the higher activation energy more, or it will increase the rate constant of the reaction with a higher activation energy more than the it will increase the rate constant of the reaction with a lower one. I don't co...

Margia Adriano 2A

Hi there! I personally really enjoyed equilibrium. I thought it was a super interesting topic, and because of that I thought it was a little easier than thermodynamics for me haha!

Margia Adriano 2A

Hi there! E naught is going to be the cell potential under standard conditions, so 1atm, 1M concentration for the solution, etc. Just regular E by itself is going to be cell potential under non-standard conditions, which we can solve for using E naught in that given equation on our constants sheet. ...

Margia Adriano 2A

Hi there! E naught is going to be our cell potential under standard conditions, while just regular E by itself is going to be cell potential under non-standard conditions. Hope this helps!

Margia Adriano 2A

Hi there! All my favorites are really just all those fiction books that we all read in elementary school haha. I find rereading all of the old faves is really relaxing, like the Percy Jackson series, or the Hunger Games trilogy. Reminds me of the good ol' days :')

Margia Adriano 2A

Hi there! The reason we do not multiple the standard cell potentials when working with these kinds of problems is because cell potential is an intensive property. This means that it does not depend on the amount of substance present. For example, the density of liquid water is an intensive property....

Margia Adriano 2A

Hi there! It will usually depend on the question being asked. If the question was asking about reaction mechanisms, it should give you the rate law so that you can answer which one would match it. It can also ask you which rate law is matches a given reaction mechanism. Overall, you can't solve for ...

Margia Adriano 2A

Hi there! The salt bridge is meant to maintain the charges of the two cells so that they are both electrically neutral. Without it, the negative charge of one cell would build up and then electron movement would stop because it is then unfavorable. Hope this helps!

Margia Adriano 2A

Hi there! In his lecture, he said that we do not need to know which specific intermediates would be used in a reaction. This is high-level stuff that would take into account a whole bunch of factors such as Lewis structures of all the species that could be compatible with the reaction. All you need ...

Margia Adriano 2A

Hi there! I'm not sure if we were both given the same numbers for this problem, but I'll just explain it with the ones I was given. For this reaction, I found that reactant A is first-order, reactant B is second-order, and reactant C is zero-order. For the rate law, I wrote that rate = k[A][B]^2 bec...

Margia Adriano 2A

Hi there! Based on what I've seen, they'll either tell you, or you can determine it from what species are present. For example, in Sapling Wk 7/8 question 4, HNO3 is present and is a strong acid, so we can assume that it's going to be in acidic conditions. Hope this helps!

Margia Adriano 2A

Hi there! I believe the standard E that you got is incorrect. Double check that you used the right potential on the chart. Fe has a couple different reactions on it that have different charge changes, so try to double check you used the right one for this problem! Hope this helps!

Margia Adriano 2A

Hi there! Oxygen is going to almost always have a -2 oxidation state when its in a polyatomic molecule/not standing alone. K is also going to almost always have a +1 oxidation state, and the same goes for all other Group 1 atoms. Knowing this, we can assume that Cl is going to have an oxidation stat...

Margia Adriano 2A

Yeah! So, with this one, you'd want to use the Nernst equation E=Edot-0.05916V/nlogQ to solve. But, to get Edot, you'd use Ecell=Ecathode-Eanode, to find Ecell of the overall reaction. From there you can apply Nernst equation to solve for E or the cell potential. This may be a dumb question. But ho...

Margia Adriano 2A

Hi there! In terms of the order, they are listed in order of what species they come into contact with. For this problem, the Pb electrode comes into contact with the PbCl2 that forms, and then Cl is listed right up against the salt bridge because that's what it comes into contact with. Then on the o...

Margia Adriano 2A

Hi there! So the anode is going to be written on the left side of the diagram, while the cathode is going to be on the right. The single vertical line indicates the different phases/species for that reaction, and the double line represents the salt bridge. Knowing that, we list the species in the or...

Margia Adriano 2A

Hi there! The reaction for Magnesium is oxidation, but its value is given when it is a reduction reaction, so you are correct to flip the sign for its potential. However, because we flipped the sign, we are going to add the cathode and anode values together instead of subtracting the anode value fro...

Margia Adriano 2A

Hi there! I believe that the above poster is correct, the Nernst equation does account for that in that it includes the ideal gas constant, which takes care of the difference in units!

Margia Adriano 2A

Hi! There are a few general rules that you can know that will help you assign oxidation numbers that I know of off the top of my head: 1. free elements are going to be 0 2. sum of oxidation numbers in an uncharged compound should be 0, while the sum on a charged compound should be the charge (like O...

Margia Adriano 2A

Hi! This is a great question, and it really encourages me to think a little ahead for classes instead of getting caught up with present classes! Usually, I consult upperclassmen or people who have taken the class already to get a better understanding for the layout of the class, how the tests are, b...

Margia Adriano 2A

Hey there! I'm doing about fifteen hours per week in terms of work, which isn't as much as some of the hard workers here, but I do find myself still struggling with balancing everything!! I won't lie and say that I'm breezing through my classes, because having to stay on top of the continuous stream...

Margia Adriano 2A

Good job, everyone! If you still have midterms, good luck on them! Awesome job to everyone for finishing this week and chem midterm 2!

Margia Adriano 2A

Hi! The salt bridge is meant to maintain the charges of both sides of the Galvanic cell so that one is not more negative than the other. As the electrons move from one side the other, their destination is going to become more negative because electrons are negatively charged. Ions will then move thr...

Margia Adriano 2A

Hi there! Just understand that this equation just relates entropy to degeneracy, where W is equal to the number of possible microstates for molecules in a system, so in other words, you've got it all to my understanding! If anyone has anyone has anything to add, please feel free!

Margia Adriano 2A

Hi! Right now, I'm watching WandaVision!!! It is soooo good and it's getting super interesting right now; I highly recommend it if you like Marvel!!

Margia Adriano 2A

Hi there! The Cp in our equation tells us that we assume constant pressure because this is the specific heat constant at constant pressure. If it were constant volume, we would use Cv, or the given equation would have Cv instead of Cp. Also, in problems that would use this equation, I would assume t...

Margia Adriano 2A

Hi there! That was my understanding of it as well, that if the curve has a maximum value/upside down parabola that the reaction would be nonspontaneous. I believe it is because as it approaches the maximum, it would be an increase in free energy, as in the reaction needs energy going in for the reac...

Margia Adriano 2A

Hi there! Delta U and Delta H are not interchangeable; they represent different things and tell us different things about a system! Delta U is the change in internal energy, or in other words, the amount of energy a system has. Delta H is the change in enthalpy, and is usually thought of as the amou...

Margia Adriano 2A

Hi there! On the constants and formulas sheet, we can see the Cp is equal to (5/2)R and that Cv is equal to (3/2)R. By substituting one equation into the other and with a little bit of math, we can find this relationship that Sapling shows. Hope this helps!

Margia Adriano 2A

Hi there! w=-deltan*RT is really only used when there is a change in moles. In this case, we are really only focused on the change in volume, which is why we solved for it using PV=nRT, and then plugging it into w=-PdeltaV. Hope this helps!

Margia Adriano 2A

can anyone explain why we can't use the original w= -P dV equation instead? i'm comfortable using the other but i don't understand why my answer using w= -P dV is wrong. Hi there! For Path A, it is a reversible isothermal reaction, so we would use w=-nRTln(V2/V1). This is because in aa reversible e...

Margia Adriano 2A

What's Wrong With Secretary Kim was an absolute banger! I loved that one, but the one I always go back to is always Weightlifting Fairy Kim Bok-Joo! I think I'm just a sucker for the university dramas ahaha!

Margia Adriano 2A

Hi, there! For this question, they are asking for the heat capacity of the calorimeter, not of the substance. Instead of using q=ncAT, you will just be using q=cAT, then plugging in the given values, and then solving for heat capacity. Hope this helps!

Margia Adriano 2A

Hi! You're correct; we do not include solids or liquids in equilibria calculations. Solids do not have a concentration, and liquids are usually the solvents in these problems, so they're concentration does not change a significant enough amount for them to be included in calculations either! Hope th...

Margia Adriano 2A

Hey! This exact thing happened to me during the midterm, so don't feel discouraged because you aren't alone with this one. I think next time, I'm going to try out the strategies that people have responded with here. I think some of it for me is also not doing enough practice problems to prepare for ...

Margia Adriano 2A

Hey! I plan on raking BL with C next quarter! Although now I'm hearing that there isn't much overlap so far, I also heard that it helps to have a base in B already.

Margia Adriano 2A

I don't know why but it feels really reassuring that I'm not the only one that finds it hard to absorb info from reading the textbook. I think I'll try to change my study habits instead of forcing myself to spend all my time reading the textbook just because it feels like that's how everyone else i...

Margia Adriano 2A

I definitely needed to hear this! Thanks so much! Super proud of you too, I'm sure you worked hard and did a great job!! Good luck with the rest of the quarter!

Margia Adriano 2A

Hey there! I'm sorry to hear that; I also find myself struggling to find a good balance that won't negatively affect my studies and my social life. However, I believe it's all little easy things that you can do to make sure your mental and physical health are getting taken care of! First things firs...

Margia Adriano 2A

Hi there! Which gas constant value you use typically depends on what the units you're working with are. For most of the problems I've seen that would be the one we're using the most so I think it would be fine to stick with that one, but it all depends. Hope this helps, and please correct me if I'm ...

Margia Adriano 2A

so for a lot of the UA step-up sessions I'm seeing A + B (front back arrows) C. Do we usually assume that the concentrations/pressures are referring to not solids and liquids? Because otherwise say A (s) would not be factored into the computation, right? Hi! Solids and liquids do not have concentra...

Margia Adriano 2A

Hi Margia! I also started by converting pH to pOH and then got a similar concentration for [OH-]. I just assumed that the concentration of [OH-] was at equilibrium and used that concentration of [OH-] to fill out my ICE table. We just don't know the initial concentration of the amine, so I used the...

Margia Adriano 2A

Sebastian2I wrote:Is this a rule without exception? Anytime the pKa is greater than the pH we should respond that more of the initial acid is present?

Hi! I believe so, and I don't know of any exceptions, but if I'm wrong please feel free to correct me!

Margia Adriano 2A

I'm also kind of stuck on this one. Should we be adding/subtracting these equations and using the inverse K value when possible? Hi! For this one, I would first figure out which equations that were given will give us the reaction at the top. I would focus on getting all of the species on the correc...

Margia Adriano 2A

Hi! I'm not sure what I'm doing wrong for this question. We are given Kb = 9.397*10 -5 and that pH=9.565. I converted pH to pOH, then found the concentration of OH- to be 3.673*10 -5 . Then I used the Kb to solve for the concentration of the base, then solved for percent protonated. I keep getting t...

Margia Adriano 2A

When working with acids and bases and conjugate acids and bases, will the acid or base always be on the reactant side of the reaction being formed and the conjugate acid or base always be on the product side? Hi! I do not think that it matters that much, as long as you know the conjugate pairs over...

Margia Adriano 2A

What's the difference between protonation and ionization then? Hi! I believe ionization refers to the actual dissociation of the acid. For example, HCl is a strong acid and would have a 100% ionization because it completely dissociates in water. Protonation refers to the process of attaching a prot...

Margia Adriano 2A

Hi there! Typically, if the pH at a given time is lower than the pKa, then you will have more protonated species. In this case you will have more HA at this given pH, which has no charge, so the solution will be more neutral at the given pH. The pKa basically tells you what the pH needs to be for th...

Margia Adriano 2A

Hi! Basically, if your pH is lower than the pKa of your acid in the problem, typically there will be more protonated species present in the solution at the time. In this case, there will be more HA, which has no charge, at the time, so the solution would be neutral at that pH. I hope this helps!

Margia Adriano 2A

Hi there! In general, yes you would use Q when you aren't sure if the system has reached equilibrium yet. Most of the time, I think the problem would state what's going on with the system, but since you find Q and K the same way (products over reactants) then I think you should be all right. You can...

Margia Adriano 2A

Hi! I believe that all reactions should reach equilibrium. For every forward reaction, there needs to be a reverse reaction and vise versa and there will always be a point where the rates of the reverse and forward reactions are equal. I hope this helps!

Margia Adriano 2A

Hi there! All you can really say for sure is that there is no strong favor towards either the reverse and forward reaction. If it gets pretty close to either end, it would be a little bit easier to say that it at least leans in one direction, but there is still no strong favor. I can say for sure th...

Margia Adriano 2A

Hi! For me, I do a lot of practice problems from the textbook. I personally think that it helps you better prepare for tests if you already know how to set up/tackle problems and overall is really helpful with applying concepts we're learning. Also, I try to do distributed studying, so instead of ha...

Margia Adriano 2A

Hi! Remember that K is just a ratio of the concentration of products and reactants, so when you increase/decrease the concentrations of either one of them, although the system does have new concentrations now, it will eventually balance itself out to match the original ratio or the K value. For exam...

Margia Adriano 2A

Hi! Genuinely, I am so tired and I don't think a two week break is enough to catch up on all of my missed sleep, but hey! Just one more week to go ahaha. How are you doing?

Margia Adriano 2A

Hi! For me, I don't usually do last minute studying because I always went by the saying "if I don't know it by now (as in right before the test), I'm not gonna know it at all." This has actually helped me avoid cramming and sleeping too late before big exams and stuff like that!!

Margia Adriano 2A

Hey!!! I'm planning on sleeping until noon everyday of winter break to catch up on all my missed sleep hours lol. Hopefully everyone can catch up on sleep before winter quarter starts!!

Margia Adriano 2A

Hi! I believe you're correct. The carbon has two hybridized orbitals that are 2sp² for the two regions of electron density. This leaves us with two unhybridized 2p orbitals for the remaining two valence electrons that make up the two pi bonds in the triple bond between carbon and nitrogen.

Margia Adriano 2A

Hi! What I do is first look at the different atoms in the salt/compound. In order to determine whether it is acidic, basic, or neutral, you have to determine if it contains a conjugate acid or base. For example, NaCN is a basic salt. The CN- anion came from HCN, which is an acid. In other words, CN-...

Margia Adriano 2A

Hi! I don't think it will change, it's just sort of there to establish that the solution is at room temperature. You can sort of disregard it for now I think!

Margia Adriano 2A

Hi! I think most of the time with acids, the name becomes whatever the anion's name was with an -ic at the end. For example, HCl: the chlorine on it's own is Cl- and is called a chloride anion and then once it's attached to the H, it becomes hydrochloric acid (the hydro was also added in because of ...

Margia Adriano 2A

It's a little bit time consuming, but I always rewatch lectures at like two times speed to see if there's any concepts or little tidbits of information that I might have missed that might be important. I'll write down little things that he says that I think might be helpful to me later on. Another t...

Margia Adriano 2A

Hi! I'm going to be studying by rewriting/organizing my notes! I don't know if this works for everybody, but for me, restructuring my notes and going over them again is really helpful for me. I also am re-watching all of the lectures again just to make sure I didn't miss any little details that migh...

Margia Adriano 2A

I feel the same way as you! I think it just takes me by surprise for how big of a chunk tests take up in our grade, especially when there's only really three that we've taken, plus the small amount of points from other assignments. I think we'll do all right though, and I wish you the best of luck o...

Margia Adriano 2A

Hi! I'm honestly feeling super nervous about the final!! Especially since this is the first one I'll be taking out of all my classes and at UCLA too! Hope you're doing all right!

Margia Adriano 2A

Hi! You should be able to tell whether a compound is ionic or covalent with a Lewis Structure. If the Lewis Structure shows shared electrons (such as single bonds or double bonds), it should be a covalent bond. Lewis Structures for ionic compounds look a little bit different in that the individual a...

Margia Adriano 2A

Hello! I was wondering if anyone can help explain the polarity stuff for this question. I am a bit confused... For each molecule, specify the polarity of the bonds and the overall polarity of the molecule. Molecules: BeCl2 and H2O Thanks! Hi! When it says to specify the polarity of the bonds, it sa...

Margia Adriano 2A

Hi! I solved this problem by converting those mass percent compositions into moles for each atom. Basically, you're being asked to find the molecular formula just like in the first unit of this course. Using the moles, we can find the empirical formula and then use the molar mass given to find the m...

Margia Adriano 2A

Hi! Yes, the bond angles are the key pieces of information needed to solve this problem. Think about it this way: both molecules are showing that there are only two other atoms attached to the central atom. In (b) with the 180 degree bond angle, think about whether it would be possible for there to ...

Margia Adriano 2A

Hi there! Tetrahedral should be the correct answer for this question. Perhaps check spelling or if they're picky about capitalizations? It should be marked correct. Hope this is helpful!

Margia Adriano 2A

Hi! I believe this is because bonded electrons are more localized, specifically to the orbital/bonding region in between two different atoms and is further from the nucleus than lone pair electrons. The lone pairs are closer/attracted to one nucleus/atom. Therefore, there is more repulsion from the ...

Margia Adriano 2A

Hi there! I believe it's really just an atom will rotate if it can rotate, as in there's not really a particular reason that they do. It might have something to do with just having energy to rotate when at a certain temperature. Just the most important thing to understand is that they are able to ro...

Margia Adriano 2A

Hi! How I would usually approach problems for this is just first seeing how many electrons we need. Then I look at all possible variations of bonds tied to the central atom, so in this case it would be a carbon atom. This can be just changing up whether it is bonded with double bonds, whether it mak...

Margia Adriano 2A

Hi! Yes, CH3F is a tetrahedral, with C creating four bonds as the central atom. The C-F bond does affect something; since Fluorine is a very electronegative atom, it makes CH3F a polar molecule. Hope this helps!

Margia Adriano 2A

Hi! All atoms that have p or d orbitals are able to hybridize in a molecule, not just the central atom!

Margia Adriano 2A

You would figure the second question out by asking yourself which of the three Lewis Structures of the carbamate ion is the least stable. To do this, you would look at the formal charges of the three structures and whichever one is more charged (as in it has more atoms with negative/positive formal ...

Margia Adriano 2A

When a Group 16 element, like oxygen for example, gains one electron, it would become O - . This means that it becomes a negatively charged ion. The electron and the now negatively charged oxygen ion now experience repulsion because they are two negatively charged particles. Although it does want to...

Margia Adriano 2A

In the Nitrate Ion Lewis Structure, there are two N-O single bonds and one double bond between nitrogen and oxygen. Nitrogen does not have an expanded octet, so it can only create two single bonds and one double bond with the oxygen atoms. It has five valence electrons, so when we set up our formula...

Margia Adriano 2A

Hi! I know that Boron and Aluminum do not need to have a full octet, but I am confused as to why this is. Is there a specific reason for it? If so, can someone please explain it to me? Thank you.

Margia Adriano 2A

A dipole is a molecule with opposite slight chargers, such as water. Dipole-dipole interactions are when two of dipole molecules interact. An induced dipole happens when two molecules interact, causing one of the molecules to be distorted and make sort of a temporary dipole. A dipole-induced dipole ...

Margia Adriano 2A

Hi! I believe that we just have to understand how to write the configurations for transition metals. I don't think knowing the exact number of valence electrons are completely necessary, but in regards to bonding for transitional metals, it would be a little more helpful to know what types of ions t...

Margia Adriano 2A

Hi there! It isn't necessary for chemists to know about them or study these higher orbitals because there are currently no observable elements that we know of that would have electrons that would land in these orbitals. I believe there is some continuity for these higher orbitals in theory and that ...

Margia Adriano 2A

I think that it is pretty helpful to determine what is a metalloid using its electron configurations, but because of the ambiguity and differences between each of the metalloids, it would be better to just know which elements are metalloids or not. Metalloids are best determined and identified in my...

Margia Adriano 2A

Hi! The two exceptions to the typical electron configuration rules are chromium and copper. I know that with their configurations, instead of filling the 4s orbital, it instead goes to the 3d orbital where it becomes the 3d 5 for chromium and 3d 10 for copper. I don't understand the reason for that ...

Margia Adriano 2A

Hi!

I believe he said that we will not be working with the f-orbitals at all. All we really need to understand how to do is from 3d orbitals and up.

Margia Adriano 2A

Hi! I suppose you could say that. The number of electrons in an atom determines how many principles shells of an atom is filled, and thus how many orbitals are filled. By s, p, d, f numbers, I'm assuming you mean the angular momentum quantum number (l), so in some way you could say that. Hope this m...

Margia Adriano 2A

Hi! The only time a 1 electron atom could ever really be in 5s would be if it was given enough energy and was in an excited state. I'd assume that if this were in a problem, you would be told explicitly it was excited or given values for you to be able to determine that it was excited. Otherwise, it...

Margia Adriano 2A

Hi! So we know that the ground state is an electron's most stable state, and that goes for its configuration as well. When we write out the configuration in the ground state, we will fill the lowest energy levels to their maximum first. For the excited electron configuration, when we are writing tha...

Margia Adriano 2A

Hi! Electron density distribution refers to the arrangement of the electrons within an orbital, not how many there are per se. The number of electrons in an orbital will be determined by how many electrons there are in the whole atom and then its distribution to each shell/orbital. The electron dens...

Margia Adriano 2A

Hi! I don't think it is too important or necessary for us to know whether an electron is spin up or down, just that you know the ms=+1/2 is spin up and ms=-1/2 is spin down and that a filled orbital cannot have two of the same. Hope this helps!

Margia Adriano 2A

Hi! I think you should try (Planck's constant)(speed of light)/(9.33*10^-6) instead of (Planck's constant)(speed of light)/(9.33*10^-4). When you divide the latter by 100 instead of doing it like the former equation, I believe you get different answers. Hope this helps! If I'm wrong, please correct ...

Margia Adriano 2A

Hi! In Lecture #10, it was concluded that s-electrons have a lower energy than p-electrons in the same shell. I am not sure about how we got to this conclusion. P-orbitals and d-orbitals have nodal planes, so that means that they have a nonsymmetric distribution of electron density, while s-orbitals...

Margia Adriano 2A

In the Atomic Spectra video we had to watch, in the key concepts it says that Rydberg's constant is 3.29x15^15s^-1 but at another point in the video Prof says its 3.29x15^15 Hz. Can someone explain the difference between the units, or why there is no difference? I believe that Hz is a derived SI un...

Margia Adriano 2A

You're given the wavelength 102.6 in the ultraviolet spectrum of atomic hydrogen, which means that the initial energy level n 1 =1. (Think about the Lyman series and how he used ultraviolet light for it.) So we have the wavelength, and now we can solve for frequency using the equation frequency = c/...

Margia Adriano 2A

For me, I study by taking notes of the lectures and doing textbook problems. Typically when I do not understand something at first, I will read the textbook and see what their explanation is for a specific concept. I also ask on here if I still don't get it. If I don't get a textbook problem, that's...

Margia Adriano 2A

Hi! I am not too sure how to word this question, but bear with me. In Lecture #7, Prof Lavelle talks about electrons passing through a crystal and how it was concluded that they show wave-like properties from that. What exactly happened when the electrons passed through the crystal for us to conclud...

Margia Adriano 2A

Light intensity in the wave model does not affect any part of the c=(wavelength)(frequency) equation. Light intensity translates to the amplitude of the waves in this model. As it was used in the experiment where they discovered the photoelectric effect, they made the light brighter (or more intense...

Margia Adriano 2A

Hi! I think this might have been answered already, but I am still a little confused about it. When doing mass percent composition, why is that we turn the percentages into grams out of 100 grams. For example, a sample that is 64.7% C would be turned into 64.7 grams in order to turn it into moles? Wh...

Margia Adriano 2A

Another thing that you can do is just avoid rounding until you get to the very end when it's time to officially answer the question and then just go by the significant figures rule or round to the hundredths place by then!

Margia Adriano 2A

For significant figures, you round to the same number of significant figures of the values that the problem will usually give you. Oftentimes, the amount of significant figures from a periodic table differs if you use different ones. Also, rounding to the same number of decimal places isn't the same...

Search found 102 matches