CHEMISTRY COMMUNITY

Sami Siddiqui 1J

I'm doing chem 14bl and chem 14c next quarter.

Sami Siddiqui 1J

Navdha Sharma 3J wrote:Right now I have been listening to 'Folklore' by Taylor Swift on repeat!

I've done this too!! Major props for that

Sami Siddiqui 1J

We put inert electrodes like platinum in cases where we observe half-cells without substances in their solid state that can pull electrons from the anode into the cathode. For example, if a half-cell only contained aqueous substances like iron(II) and iron(III) ions in solution, then there wouldn't ...

Sami Siddiqui 1J

First, let me say that the internal energy of an ideal gas can be contributed by the kinetic energy of the substances in our system at hand. This kinetic energy can be broken down into three different categories: translational motion (movement as a trajectory motion), rotational motion, and vibratio...

Sami Siddiqui 1J

I deeply sympathize with your situation, Garmani. To that end, I still must emphasize that, in light of your difficult situation, you've got to dig deep (perhaps deeper than you've ever done) to really hone in that last bit of motivation you may still have to finish strong this quarter. Take this as...

Sami Siddiqui 1J

Based on what I've seen in a previous forum post, the free energy of activation takes entropy and enthalpy into account because it directly refers to the concept of free energy. Activation energy itself, on the other hand, only takes enthalpy into account.

Sami Siddiqui 1J

I was pleasantly surprised by this midterm, now I'm just working to keep up the same momentum for the final.

Sami Siddiqui 1J

Wednesday's lecture covers this well but the graphical approach to determining a reaction order is to observe which plot generates a linear function with respect to time. For example, a first order reaction is linear when ln[reactant] is plotted against time.

Sami Siddiqui 1J

I can't point to a specific song but I'd say most of the music I've listened to this quarter has been from Michael Jackson, Taylor Swift, and Harry Styles.

Sami Siddiqui 1J

I would say chemical equilibrium.

Sami Siddiqui 1J

I did all the instructed textbook questions and sapling questions twice for my chem 14a final. I also reread sections of the text that pertain to questions I had the most difficulty answering.

Sami Siddiqui 1J

I'm primarily involved with Al Talib, UVP, and Sports Medicine Club.

Sami Siddiqui 1J

What I normally do to prepare for a given section is to pre-note the textbook. This allows me to get a basic picture of what we'll be discussing when Dr. Lavelle posts his lectures. Of course, when you're going through the text the first time, a lot of things aren't going to make too much sense. But...

Sami Siddiqui 1J

I'd use this if you need it:

https://sites.google.com/site/chempendix/potentials

Sami Siddiqui 1J

n in this case represents the moles of electrons transferred in the redox reaction process. Keep stoichiometric coefficients and the change in signs in mind when determining this number.

Sami Siddiqui 1J

The post will count for Week 7. Any posts made between Monday and the next coming Sunday by 11:59 PM will count for a given week.

Sami Siddiqui 1J

One of my favorite foods is a Pakistani/Indian dish called nihari; it's basically a beef stew and it goes really well with bread (otherwise known as naan).

Sami Siddiqui 1J

Ecell refers to the potential difference at a given point in a reaction and is subject to change by virtue of Le Chatelier's Principle. The Ecell(0) is standardized; it'll never change regardless of the progress in a reaction.

Sami Siddiqui 1J

I believe that the n is not exactly moles of a substance, but moles of a particle. Therefore, I don't believe that n has any units since it is just a given number of particles. I am not exactly sure of the reason but that is my best guess! That would make sense as well since the equation (deltaG)=-...

Sami Siddiqui 1J

The above comments made are absolutely right on this one. When it comes to breaking down the oxidation numbers for an ionic compound like KClO2, I usually treat the cations and anions separately. For example, if we look at ClO2- only, we'd find that the oxidation number of Cl is +3: oxidation number...

Sami Siddiqui 1J

That should be correct. Irreversible reactions reflect a change in temperature while doing expansion work, whereas reversible reactions constantly replenish the energy expended by the system as work with heat from the surroundings.

Sami Siddiqui 1J

I'm doing Chem 14C, Chem 14BL, and bmd res 5ha. I'm also doing a random GE to pad up my unit count.

Sami Siddiqui 1J

Delta H equals q at constant pressure. Given that delta H = delta U + P*delta V, and because delta U = q + w = q - p*delta V, substituting delta U will cancel the P*delta V term, so what you're left with is delta H = q.

Sami Siddiqui 1J

In the long run, to have a negative delta G value means that K (the equilibrium constant) will be greater than 1, meaning that the equilibrium concentrations will favor the products over the reactants as the reaction approaches equilibrium. This is given by the fact that, on a conceptual level, K is...

Sami Siddiqui 1J

Positive entropy indicates that there's greater disorder that occurs as a result of the reaction. The greater the value, the more complex the reactant is because more disorder can be created from a system that is initially more ordered than others. Negative entropy, conversely, indicates that the re...

Sami Siddiqui 1J

I'm fairly certain that Casey is the only professor that is available for next quarter. At least, that's what it shows on my class planner.

Sami Siddiqui 1J

I'm not sure how useful this would be at this given moment, but what I normally do is that I pre-note all the essential textbook sessions before Dr. Lavelle gets to introduce it so that nothing is exactly new; you'd basically be using the lectures to review what you know and patch any gaps in your k...

Sami Siddiqui 1J

You used the wrong delta H value for water; I believe that value is for the liquid state of water, when in fact, the delta H value for water vapor is somewhere around -280. Consult the chart for the exact value and be cautious of the compound's state.

Sami Siddiqui 1J

Picking the right equation is mostly just making sure you pay attention to the stipulations of the reaction stated in the question. As you've mentioned, there's a lot of equations in these past 2 outlines, which is mostly a testament to the fact that we have nearly equivalent forms of equations for ...

Sami Siddiqui 1J

Midterm 2 will basically cover Outlines 3 and 4 until this Friday's lecture. Like the last midterm, it probably won't cover any new material learned in the same week of the test.

Sami Siddiqui 1J

I would say to attend as many of the UA sessions as you can, prioritizing sections that cover topics that you are least familiar with. I'd also watch the Organic Chemistry Tutor as well; that channel is a lifesaver!

Sami Siddiqui 1J

I thought the grades were being posted tomorrow, but I guess it's for the better if they are updated today.

Sami Siddiqui 1J

The Chemistry Community points have been updated so I'd advise that you check that on myUCLA.

Sami Siddiqui 1J

There isn't a curve; the points you earn are independent of the class performance.

Sami Siddiqui 1J

I think it's more conceptual if anything. By saying that work is the integral of P*dV between two values of volume (v1 and v2), we are basically saying that the area under a pressure (y-axis) vs. volume (x-axis) curve is the net work that has either been done to the system or that the system does to...

Sami Siddiqui 1J

So for the flask example, there are two states that a molecule could be in: either on the left side of the flask, or the right side. Degeneracy is the number of ways of achieving a given energy state, so with one molecule in that flask, degeneracy is 2, because the molecule could be either on the l...

Sami Siddiqui 1J

I felt pretty good about the midterm. There were definitely a couple questions where I really had to sit and think but, other than that, I think it went well. Let's hope that reflects in the scores.

Sami Siddiqui 1J

Keep your chin up! It's just the first midterm, so, as everyone else in this thread already mentioned, there's plenty of opportunities to boost your grade as necessary. I myself had a similar experience for a different class this quarter and, by navigating through this type of adversity, I was able ...

Sami Siddiqui 1J

Amphoteric means that a given substance can react with an acid or base, whereas amphiprotic just refers to the fact that a substance can either accept or donate a proton. Although they sound the same, note that not all amphoteric compounds necessarily have to gain or lose protons to act as both an a...

Sami Siddiqui 1J

There are some 10 pt questions on the upcoming midterm. Partial credit (5 pts) is awarded for answers to those questions that get some but not all of the steps right.

Sami Siddiqui 1J

I mostly listen to alternative and neo-psychedelic/soul music (Tame Impala, Dayglow, Khalid etc) or anything that just makes me feel good! But I've been listening to Frank Ocean, Brent Faiyaz, and Harry Styles lately :) Harry Styles is amazing!! He's one of my favorite artists! Khalid is a good art...

Sami Siddiqui 1J

Lofi hip hop is great for studying in my personal opinion. Any instrumental music in the background helps for that matter.

Sami Siddiqui 1J

Hey, can you show me the chemical formula for nitrogen monoxide?

NO

Okay, then what about sodium hydride?

NaH

Not even sodium hypobromite?

NaBrO

Sami Siddiqui 1J

This question was trippy for sure; I spent a lot of time working on this one. I think the one thing that messed with my calculations was that the book said the Kc of the reverse reaction was 6.1e23, which makes no sense. The answer key uses a different Kc value (6.1e-3), so keep that in mind. Using ...

Sami Siddiqui 1J

To answer both questions of concern, I think the midterm will be taken in our respective lecture times. The material covered in our upcoming exam will probably feature stuff up until the end of Week 3; that's how it was done in 14A, so I assume the same will be done here. Since he combined the sapl...

Sami Siddiqui 1J

There really isn't a specific cutoff. However, keep in mind that H2SO4 is the only exception when it comes to neglecting the Ka2 value in pH calculations. Because the acid is strong and polyprotic, H+ protons will not only be released to form HSO4-, but also SO4-2 in quantities that we just can't ig...

Sami Siddiqui 1J

This question can be made to look tricky by throwing in a letter as an equilibrium partial pressure, but it's nothing different from other questions we've seen. If you make an ICE table, you'd place the value p as the equilibrium pressure value for N2 under the E column. Because we haven't started w...

Sami Siddiqui 1J

To answer both questions of concern, I think the midterm will be taken in our respective lecture times. The material covered in our upcoming exam will probably feature stuff up until the end of Week 3; that's how it was done in 14A, so I assume the same will be done here.

Sami Siddiqui 1J

I agree with many of the points other students have said. In my personal experiences from Chem 14A, I found it most useful to do the textbook problems twice over. I normally complete the textbook questions as Dr. Lavelle discusses the topics in lecture and once more starting a week before an upcomin...

Sami Siddiqui 1J

The ratios would only be the same if we set the partial pressures to the power of their stoichiometric constants. Doing this would give us the equilibrium constant for this reaction, which can only change with temperature; this is how we find the answer to parts d and e of this question. Focusing ba...

Sami Siddiqui 1J

If you add more reactants, the reaction will favor the products and vice versa in order to satisfy Le Chatelier's Principle. As a rule of thumb, if you add more of a compound on one side of a reaction, then the reaction will want to remove that sudden stress by using that compound in reaction.

Sami Siddiqui 1J

On a quantitative level, we can see if an acid or base is weak if we look at its Ka (or Kb) value. As these values increase, the value of pKa (or pKb) decreases and the strength of the acid or base respectively increases. As the values of Ka or Kb become smaller, the pKa and pKb values increase and,...

Sami Siddiqui 1J

You can find the Ka value for this quesiton by looking at Table 6D.1. It has values specific to cations acting as acids.

Sami Siddiqui 1J

I used a graphing calculator for all my exams in Chem 14A and had no issues. Just as long as you aren't using some wacky programs on your calculator or cheating in any way, you will be fine.

Sami Siddiqui 1J

You will get points for doing both components.

Sami Siddiqui 1J

Any of the Star Wars films are a great option to be honest. I also enjoy any Disney Renaissance film whenever I need to unwind; my personal favorites are Aladdin, The Lion King, and Beauty in the Beast in that order.

Sami Siddiqui 1J

I got tripped up on this one, too. The most important thing to remember is that, when you try neglecting the term "-x" in your equilibrium expression, you have to check to make sure the % ionization is less than 5%. In this question, if you were to find the % ionization while neglecting th...

Sami Siddiqui 1J

I think the most important thing you must do to keep your motivation is, as cliched as it sounds, to save time for yourself. I understand that it may be difficult for you to do so because it seems like everyone's always doing something productive, even in the later hours of the night. Regardless, I ...

Sami Siddiqui 1J

If the K value is generally 10^-4 or smaller, we can assume the change in concentration (x) that we write in our equilibrium tables is negligible in our calculations. This will make it easier for us to make calculations for the equilibrium concentrations of our reactants and products because we won'...

Sami Siddiqui 1J

For me, I normally take notes on the content of an upcoming outline before Dr. Lavelle covers it in lecture. You don't have to understand everything when you go through it the first time because his lectures will essentially tie any loose ends that you may have regarding a particular section. Also, ...

Sami Siddiqui 1J

a) is actually endothermic and b) is exothermic. If H is negative, it is exothermic and therefore heat is released as a product. If H is positive, it is endothermic and heat is added as a reactant. When the temperature is increased, it will cause a shift towards the side with less heat. Hope this h...

Sami Siddiqui 1J

Until you're able to fully access Sapling, you can't do homework yet. However, as plenty of other people have just mentioned, there's ample time to get this fixed up so you don't lose any credit on your homework assignments. For many of us, myself included, there have been some technical issues when...

Sami Siddiqui 1J

I think knowing this is pretty much outside the scope of this class. However, if you haven't taken LS30A yet, you'll actually find out there when you start covering equilibria.

Sami Siddiqui 1J

The user control panel likely isn't functioning the way it should so I just re-registered a new alias under the same UID. Because you're using the same UID, all your previous posts will be saved, so there's nothing to worry about there.

Sami Siddiqui 1J

I can't think of an explicit chemical reaction where the equilibrium concentration of reactants is greater than products; however, I can point out a scenario in which this may be possible. Let's say you have an exothermic reaction such that: R \leftrightarrow P + heat If this reaction was at equilib...

Sami Siddiqui 1J

If you haven't seen the email already, Dr. Lavelle plans to give an extra 10 bonus points (capped at 180 pts, 100%) for all of us, so that's some good news.

Sami Siddiqui 1J

To solve this, we need to break up the salt into two components: the cation and the anion. If we did this in part a, for instance, we'd get Na+ and C6H5O-. Knowing from Dr. Lavelle's lecture that Na+ (or any Group 1 or 2 cation for that matter) does not significantly change the pH, we can simply ign...

Sami Siddiqui 1J

We can calculate pH if we're given the value of H+ concentration: -log(H+) = pH We can calculate pOH if we're given the value of OH- concentration: -log(OH-) = pOH The relationship between acid strength, the Ka, and pKa is very simple. The higher the acid strength, the higher the Ka and the lower th...

Sami Siddiqui 1J

Honestly, the Organic Chemistry Tutor is your best bet. I would also recommend Khan Academy as well. I used it for my AP Chem exam a couple years back and it worked very well.

Sami Siddiqui 1J

Strong acids are able to completely deprotonate, which means that all of the acid molecules can release a proton when making contact with a base in solution. Weak acids do not completely deprotonate, which means only a fraction of the molecules will actually give off protons to bases in solution. St...

Sami Siddiqui 1J

I noticed in the two midterms we've completed that most questions are, indeed, modeled on the homework questions. If you do those, you'll be set for sure.

Sami Siddiqui 1J

We will probably have to memorize the names of the ligands provided on the sheet. It's also advisable that you know which ones are polydentate.

Sami Siddiqui 1J

Hi! I simply count the number of the ligands and that gives you the coordination number. I do this, too. I also consider the fact that some ligands are polydentate, which means that a given ligand atom may be able to attach to more than one site. There isn't really a methodical way of noting when o...

Sami Siddiqui 1J

Memorize the ligand names and really just memorize the blue blurb in the textbook that goes over the process of writing formulas and naming compounds step-by-step.

Sami Siddiqui 1J

The central atom in any coordination compound is always going to be the transition metal cation. To find the coordination number, you just look at the ligands that are next to the metal in the bracketed formula and count them. While counting, you must be cautious of the fact that some of the ligands...

Sami Siddiqui 1J

Complex ions, as far as I know, are literally just coordination compounds but with charges. An example of this would be a hexaaquacopper(II) ion, which is listed in the textbook. So, in general, coordination compounds can be classified as neutral complexes or complex ions with a certain charge.

Sami Siddiqui 1J

Thank you so much, Hannah! You came in clutch with this resource for sure.

Sami Siddiqui 1J

I came back to this thread just to say that Star Wars: The Clone Wars is the move. For anyone with Disney+ and at least a slight interest in sci fi narratives, this series is perfect.

Sami Siddiqui 1J

For me, I usually designate a decent amount of time to take study breaks from doing a ridiculous amount of practice questions. It's very helpful to realize that, in the end, stressing about the test isn't going to do much good for you physically nor will it likely end up bolstering your performance....

Sami Siddiqui 1J

Annika Tamaki 3L wrote:On Lavelle's website, he has a list of ligand names, so if we are supposed to memorize anything, it is likely his list.

This is a very smart way of seeing it. I'm probably going to do this myself.

Sami Siddiqui 1J

Dr. Lavelle addressed this exact issue in today's lecture. In this class among many chemistry courses we'll be taking in the future, we'll be replacing the -ide suffix with -o, so chloride becomes chloro. Chlorido is technically correct by IUPAC standards, but we're just not using it here.

Sami Siddiqui 1J

There isn't a specific place to find these answers; instead, you must contact your TA to discuss your answers. I'm also fairly certain that Dr. Lavelle is going to cover the most commonly missed questions as our finals loom closer.

Sami Siddiqui 1J

I'm feeling great right now, thanks for asking! I've honed in my focus this quarter and look to be finishing strong heading into our upcoming finals. I hope everyone is doing well!

Sami Siddiqui 1J

The points update every so often to reflect the number of points we should've earned by a given checkpoint. So, for instance, people who completed at least 35 posts by the end of Week 7 should be seeing 35 pts under their grade. Of course, by the end of the quarter, we should have at least 50 posts,...

Sami Siddiqui 1J

Yes, this would be the case because of the lone pair. Because the lone pair would make the dipole vectors uneven, we would get a polar molecule.

Sami Siddiqui 1J

The final is going to be held over the weekend. I would need to double check the date but I'm pretty sure it's December 13th.

Sami Siddiqui 1J

I'm not exactly aware of how this grading curve works. Can someone please clarify because I thought the points we earned individually was the only thing that was being factored into grading.

Sami Siddiqui 1J

To best answer this question, consider the following circumstance: If we had a molecule where the central atom had 3 regions of electron density, then we know that the hybridization notation is sp2. This means that one s and two p orbitals were mixed. Because a p-subshell contains 3 orbitals, that m...

Sami Siddiqui 1J

The convention doesn't really matter in this case. I usually just say sp3d because it sounds better and I've seen this notation more frequently in textbooks.

Sami Siddiqui 1J

I'm pretty sure what you said should work fine. I do think it's necessary to mention all this though. Oxidation numbers are typically distinct from the concept of formal charge. It must be kept in mind that formal charges exaggerate "covalent character" by delegating one electron to each a...

Sami Siddiqui 1J

Hi Brendan, I optimized my success on these midterms by doing the following things: 1. Attending UA workshop sessions. They are incredibly useful for additional practice and to clarify any little misconceptions. 2. Reading through notes I've taken in my textbook so I don't have to sit through and re...

Sami Siddiqui 1J

The final is definitely cumulative, so plan accordingly!

Sami Siddiqui 1J

I can confirm that I got an answer of 10 electrons, as Victor had said earlier. There were two single bonds and three lone pairs in the central chlorine atom, so 5 * 2 = 10 electrons surrounding that chlorine atom. It can be confusing given that we associate one electron for a bond if we were to cal...

Sami Siddiqui 1J

The only possibility I could consider for part b in which we can see a linear geometry with lone pairs is if we had an octahedral electronic arrangement with 4 lone pairs. That way, we'd be left with two atoms to be oriented directly across from each other to minimize the amount of repulsion. Edit: ...

Sami Siddiqui 1J

I wasn't so sure either, but I'm sure this past Chemistry Community thread may be able to answer your question:

viewtopic.php?t=37869

Sami Siddiqui 1J

As a final clarification, the molecule as a whole is nonpolar, but the bonds themselves are polar. If you need a further explanation of this, I actually found a past Chemistry Community thread on this exact subject:

viewtopic.php?t=23561

Sami Siddiqui 1J

I thought Si has only 2 double bonds, one with each O, which would give it a formal charge of 0. Why does it have a lone pair? I realized that I assumed Si to have 6 valence electrons instead of 4. That is my mistake. The Lewis structure would be linear. If that is the case, I'm actually not quite ...

Sami Siddiqui 1J

Dr. Lavelle mentioned that the quantum number component and Outline 3 in its entirety is to be focused on for this midterm. Anything else would simply be unnecessary.

Sami Siddiqui 1J

The lectures will probably be asynchronous. Because of this, I heard that if you get on the waitlist for 14B, you can still get admitted into the class. If this is true, then a lot of us can still clinch 14B even with the second pass for enrollment.

Sami Siddiqui 1J

The Lewis structure of SiO2 is such that there are two Si-O double bonds and one lone pair with the Si atom. Because of that lone pair pushing the other two regions of electron density closer to each other, the shape of the molecule isn't exactly symmetrical. As a result, there will be a permanent d...

Search found 165 matches