CHEMISTRY COMMUNITY

Nick Pascua 2L

Forsure hydrogen. It is the lightest in its gaseous form and will produce the most disorder within a system, thus it has the highest entropy.

Nick Pascua 2L

I honestly didn't think this final was as hard as last quarter's final. A lot of it was plug and chug if you knew what you were doing; the conceptual weren't that hard either. I would say this test is really fair. As for my preferences, I would say online tests are better since they're multiple choi...

Nick Pascua 2L

The activation energy for both forward and reverse processes will be lowered when a catalyst is introduced. Thus the rates to convert back to each whether it be from reactant to product or product to reactant will be faster since less energy is needed for the reaction to completely take place.

Nick Pascua 2L

Hi,

Since the Boltzmann equation is S=Kb*ln(W), the W typically has larger errors because it's a potential estimate of different states of arrangement. However, I believe taking the natural log of W creates less errors of W and is the reason for also producing a smaller error of S.

Nick Pascua 2L

Hi Garmani, I am so sorry about your situation. Honestly, it's so hard to even imagine being in your situation trying to stay focused when the world around you is moving at different paces. All I can say is thoughts and prayers to you, please don't feel bad about not being prepared for finals, you'r...

Nick Pascua 2L

Oh my.. I didn't realize this, I forgot about daylight savings, thank you Simran for reminding me !!

Nick Pascua 2L

A first order reaction has a rate that is proportional to one of the reactant's concentration while the 2nd order reaction has a rate that is proportional to either 2 things of a reactant, if a single reactant's concentration is squared or if there is a product of two reactant's concentrations. The ...

Nick Pascua 2L

Hi! No, intermediates do not occur in all reaction but they are present quite often. To determine if certain molecules are intermediates in a reaction, simply see if they are produced as a result of one reaction but also get used up in another reaction, as to where they are both a reactant and produ...

Nick Pascua 2L

Hello,

You cannot include intermediates because they are on both sides of the equation, meaning they are produced and then used again by the reaction or vise versa. Intermediates will just be canceled out in the overall reaction.

Nick Pascua 2L

Hi, Gibbs Free Energy is one of the main functions that defines Thermodynamics, combining both enthalpy and entropy in one equation to explain the transfer of energy. Breaking down thermodynamics, thermo means "heat" while dynamics can mean "movement, activity, change, etc." Thus...

Nick Pascua 2L

Hello,

The electromotive force (EMF) is not always equal to the maximum potential difference, but when it is equal, the current flow is cut off and no energy is passing through.

Nick Pascua 2L · Re: Final Hello, You can find it on MyUCLA but Sunday March 14, 2021 8am-11am.

Hello,

You can find it on MyUCLA but Sunday March 14, 2021 8am-11am.

Nick Pascua 2L

Hello, First, you want to take into consideration of all of the oxidation states of all the species in the equation, see how part of the reaction is being reduced or oxidized. Next, before you split into two half reactions, you want to take chlorine out of the equation on both sides because the oxid...

Nick Pascua 2L

Yes, the oxidizing agent will be responsible in reducing its own substance content while the reducing agent will do the opposite with oxidizing its own substance content.

Nick Pascua 2L

Yes! But it will take many many years for graphite to turn into diamond as it has an extremely high activation energy.

Nick Pascua 2L

Hi!

For 4F.9, instead of using volumes, just replace them with the given pressures! It would be deltaS=n*R*ln(P2/P1). The P is in atm, so also remember to use the correct R value of 0.08206 (L*atm)/(K*mol). Hope that helps!

Nick Pascua 2L

Hey!

I simply try to not think about it. There is nothing you can do to change your score until you see it so you should definitely try to divert your attention to something else! It doesn't help your mental state to stress about it. Lastly, don't worry you're not alone! Best of luck :)

Nick Pascua 2L

Hi! I too didn't do well on my 14A final but after talking too many people, I would say redoing the textbook problems is absolutely necessary as there are many diverse problems that will help you master the topics. By understanding and learning how to approach every problem, you'll increase the like...

Nick Pascua 2L

Hello, I don't think that there are any differences in terms of one of them being better. They both serve the same purpose and will function correctly. However, the porous disc requires the beakers to be connected to each other whereas the salt bridge can be done from a certain distance between the ...

Nick Pascua 2L

Isabelle Hales 1J wrote:Hi! Going off of this, is the melting point also found at equilibrium (deltaG = 0)?

Yes, I believe so. As stated above, although both processes are dealing with different state changes, the change in temperature is zero and thus the entropy, Gibbs free energy, and change in enthalpy is zero.

Nick Pascua 2L

Hello, I doubt there will be a certain time where all summer classes will end up having professors next to the course name, but even if by then, they would probably have been filled up, especially the science classes. If you are really serious about taking a specific course, then I think it's import...

Nick Pascua 2L

Hello, In the textbook problems, specifically 4H, there's a lot of comparing molecules and seeing which have a higher entropy. According to the Atkins solutions, it says molecules that are typically less rigid or are bigger in size compared to other molecules have higher entropy. Can anyone explain/...

Nick Pascua 2L

Hey! To solve this problem, all you do need is the final and initial volume as well as the amount of moles, which indeed it gives. Given that the value of the final volume is 1/5, this would mean that the original volume is just 1 (since it is 1 whole and the final volume is compressed to a fifth of...

Nick Pascua 2L

Hi!

Yes I believe so! As stated above there was a UA session on Veteran's Day so I wouldn't see why there won't be a session this Monday.

Nick Pascua 2L

Hello, There are many ways you can tell if it is irreversible or reversible. Depending on what's given in a problem, it can either: - directly tell you -tell you what type of system it is (isothermal, closed system,etc.) -show you a picture of the system -tell you certain key words, such as a variab...

Nick Pascua 2L

Hi, In some of the textbook and Sapling problems where there is a fraction coefficient next to "R," representing constant pressure or constant volume molar heat capacity (Cp,m or Cv,m), will we be expected to memorize some of the R values with their fractions? Such as the Cp,m or Cv,m of w...

Nick Pascua 2L

Hello,

I don't know if I can understand your question fully, but if I were to answer your first question, Delta U will equal 0 whenever the system has constant temperature. The internal energy aka Delta U is dependent on temperature change, and if delta T is 0 then Delta U will 0.

Nick Pascua 2L

Hi, This may be a weird question but when considering positions of simple 2-state molecules, why is it only limited to left and right and not other positions like up and down? For example, in Lecture #12, the Carbon Monoxide molecule could be seen as C-O (Carbon on the left) or O-C (Carbon on the ri...

Nick Pascua 2L

Hello, From Lecture #12, Dr. Lavelle put in his slides that within an isolated system, degeneracy (W) will reach its maximum and thus entropy will reach its maximum. I know that in an open system this can't be true but what about a closed system with constant volume? How does this differ compared to...

Nick Pascua 2L

I noticed this hasn't been said yet in this thread but I love watching The Organic Chemistry Tutor's videos on Youtube! He goes over a lot of fundamental topics and useful calculations that will help you understand the material better!

Nick Pascua 2L

Hi! Since they are not in the equations sheet, I would recommend memorizing them; this can be done through constant application in problems. You can also remember the basic formulas/equations and manipulate them through substitution. A lot of these equations though are pretty much self-explanatory I...

Nick Pascua 2L

Hi! I don't know if I'm really answering your question but textbooks problems are honestly your best bet to prepare for the midterms. I like doing Sapling to understand the content but those type of problems hardly show up on the test compared to the textbooks problems. To understand every problem t...

Nick Pascua 2L

Hey! I also have some trouble too taking tests with my house full of siblings. I don't know if your scenario is the same, but either way I am a strong believer in pre-exam or motivating meditations. Meditations in general allows me to clear my mind and focus only about what's to come on a test. Or.....

Nick Pascua 2L

Hello,

A neutralization reaction is when a strong base and strong acid react to form products of salt and water.

Nick Pascua 2L

Enthalpy is a measurement of heat transferred within systems while entropy represents random disorder within a system.

Nick Pascua 2L

Hi!

I am taking 14C next quarter along with 14BL as I've been told by my upperclassmen friends that they compliment each other well.

Nick Pascua 2L

Hi,

Yes! Anything in its gas state (except noble) contributes to the pressure of the system and takes up volume. So yes it is part of the K expression.

Nick Pascua 2L

Hello, I think to help you understand it better, the formal concentration is basically the known initial concentration when you draw the ice table. Remember back in lecture #6, to calculate percent ionization, specifically for weak acids, you have to calculate the (concentration of the conjugate bas...

Nick Pascua 2L

Hi, Delta U represents the internal energy within a system, which is specifically heat (Delta H) under constant volume/constant pressure conditions. So if there is constant volume/pressure, then Delta U is essentially Delta H. As for calculating enthalpy, just use the typical Delta H equation. Hope ...

Nick Pascua 2L

Hello, Yes, it is exactly that. Basically, as we go from right to left from the chart he gave, we are releasing heat as the state changes from a gas to liquid to a solid. Keep in mind that heat is used to break apart the molecules while heat on the other hand is used to combine the molecules or soli...

Nick Pascua 2L

In lecture #6, Dr. Lavelle said that if the H3O+ concentration is less than 10^-7, we have to consider the solution to be neutral with a pH of 7. So to clarify does this mean the same thing if the OH- concentration is less than 10^-7? If so why?

Thanks !

Nick Pascua 2L

Hi! I was looking at the problem and the answer key, and it specifically stated that "the second ionization is complete" so that's why they did an ice table to account for the SO4 at equilibrium, which was also x and is added to the .15M in your answer. Without accounting for SO4 (which is...

Nick Pascua 2L

Hey! This is an interesting question. For some of the problems in the textbooks I assumed if they didn't state otherwise there was no temperature change at all and it stayed constant. Would you mind sharing an example of one of these problems? I don't think it's a good idea to assume that all reacti...

Nick Pascua 2L

Hi,

For some of the questions in the textbook that use the table 5G.2, what is the difference between "K" and "Kc(+/-)?"
Some of them have different values but I'm not sure why.

Thank you!

Nick Pascua 2L

Hi,

I'm having trouble understanding this but what's the difference between the acidity constant (kA)and the basicity constant (kB)? From the lecture I'm assuming it has something to do with the compound in the denominator of the equilibrium expression? How can you tell or what do you look for?

Nick Pascua 2L

Hi, Yes, as said above pKw will equal both the sum of the pKa and pKb values. But also remember that acidity/basicity constants are Ka and Kb respectfully, so the difference between these two and pKw is that the pKw includes the (-log) and the other two don't. So that's one way to look at it. Hope t...

Nick Pascua 2L

Hello,

What happens when you add an inert gas in a closed container with the following conditions?
a) constant pressure
b) constant volume

Nick Pascua 2L

An inert gas is a gas that does that not react with any other chemicals. If you can recall from 14A, these are the noble gas elements found in the last column of the periodic table (He, Ne, Ar, etc). They have full valence electron shells thus they do not react. With that being said, adding an inert...

Nick Pascua 2L

Hi!

Solids and liquids are not included because their concentrations will always stay consistent throughout a reaction. Thus their values will not change the equilibrium constant.

Nick Pascua 2L

Hi, I noticed in Dr. Lavelle's lectures, he had equilibrium "sits to the left" when there are more reactants at equilibrium. Would this mean since there are more reactants then the system would shift to the right to balance the products and reactants? To sum it up, what's the difference be...

Nick Pascua 2L

Do the Q and the K values follow the same trend/pattern when describing on whether a system will favor reactants/products? For example in the lecture, it states if K is small, then it would favor the products (shift right) since there's more reactants at equilibrium. And if Q is smaller than K, the...

Nick Pascua 2L

Do the Q and the K values follow the same trend/pattern when describing on whether a system will favor reactants/products? For example in the lecture, it states if K is small, then it would favor the products (shift right) since there's more reactants at equilibrium. And if Q is smaller than K, then...

Nick Pascua 2L

Hi!

Yes I believe that is correct, since any change in pressure and the concentration will just end up undoing the stress that was made but not changing the K value.

Nick Pascua 2L

For a gas to be considered ideal, it would have to have negligible volume (which can't really be present in real life since all gases possess some sort of volume within a system), the particles would have to be move randomly and have to be equally sized with no form of intermolecular forces between ...

Nick Pascua 2L

Hi!

There are different ways to find the charge of ligands. However, it depends on the ligand. Some require just memorization or drawing out the Lewis structures to see if it makes sense. Others you can figure out by doing math from multiple elements/compounds found in complexes.

Nick Pascua 2L

Hello, The strength of an acid is typically determined by how easy it is for acids to release H+ protons. I wouldn't really focus on electronegativity, as there are different patterns to how the trends go. For example, halogens directly attached to hydrogen has a different trend than oxyacids. But i...

Nick Pascua 2L

Hi, I think it's because acetic acid has a methyl group while formic acid has a carboxyl group. With that being said, formic acid does not have an electron-donating group unlike acetic acid in which the CH3 (methyl grou) contributes electron density to the O-H bond thus making it harder to remove th...

Nick Pascua 2L

No there isn't any. Everything was worth 6 points on the final plus 10 extra points.

Nick Pascua 2L

Hi,

No there is not, but if you look at the syllabus you can calculate the points you've earned so far.

Nick Pascua 2L

Hello!

The coordination number is simply the number of bonds in a compound!

For example, in the lecture, [Fe(CN)6]^4-, the coordination number would be 6, as there are 6 (CN)'s attached to Fe inside the bracket.

Nick Pascua 2L

Hi! To find oxidation numbers, you need to do a little bit of math. In an overall case where a compound is considered neutral, charges have to be equal to 0. For example, if we have CO2 (a neutral atom with no overall charge), the overall charge has to equal 0. In many cases in 14A like Coordination...

Nick Pascua 2L

The COOH is called a Carboxyl group and this gives away protons (the H+) in reactions. Carboxyl acids are typically anything with COOH and an R-group attached and like Lillian above also said it is considered a weak acid.

Nick Pascua 2L

Hi!

Can someone please explain to me what the purpose of using prefixes "bis-, tris-, tetrakis-" were for again? Dr. Lavelle said we can't use "di-di" and I'm not really getting what he means by that.

Thanks!!

Nick Pascua 2L

Hi! Ivan is right. Adding another lone pair where there are 2 bonds and 2 lone pairs would cause a bent structure to be linear again. Just remember that adding 1 or 2 lone pairs to a linear structure will cause it to bend, but adding a 3rd will even out the push in electron densities. I hope that he...

Nick Pascua 2L

Hello,

I believe the charges do not matter when considering dipole vectors. All oxygen atoms will have the same electronegativity value and since it's a tetrahedral, yes they will all cancel out.

Nick Pascua 2L

I thought the shape is a square planar, not trigonal bipyramidal because it has a total of 6 electron densities with one as a lone pair. Hi! A square planar will have 6 electron densities and 2 lone pairs. The shape that Molly showed is a square pyramidal since it has 6 electron densities and 1 lon...

Nick Pascua 2L

Hi,

On Sapling Question #16, what does it mean by delocalized pi bond? How do you know which molecule will have this?

Thank you.

Nick Pascua 2L

Hello,

A pi bond is formed between the p lobes of adjacent atoms. Each p orbital has two lobes that can hold a total of two electrons, thus there's only one bond.

Hope that helps!

Nick Pascua 2L

Hi! So based on the problem and using the same element, it'll be a lot of plug and chug but also keeping track of how and where you want to place your charges, you just have to make sure that the overall charge is +1. There's different ways to do this. For example if I were to write 5 N's in a row l...

Nick Pascua 2L

Hi !
This molecule would be linear.

Nick Pascua 2L

Hello,

I believe he means that lone pairs can easily occupy a greater volume of space around an atom compared to bonding pairs since lone pairs are only limited to attracting to only one nucleus and not multiple atoms' nucleus.

Nick Pascua 2L

Hi, the Cl02+ ion can be drawn in 3 ways. 1) With 2 double bonds, the formals charges would be +1 on the Cl and 0 for the Os. 2) With 2 single bonds, the formal charges would be -2 on the Os and +3 on the Cl. 3) With 1 double and 1 single, the formal charges would be +2 on the Cl, -1 on O attached t...

Nick Pascua 2L

Hello, Ample means "enough/more than enough" while overwhelmingly means "too much." In terms of bonds, an atom that has an overwhelming amount of electronegativity will cause a bond to become more ionic or there would be an overwhelming pull towards a specific atom. Thus, overwhe...

Nick Pascua 2L

remember that in the periodic table, anything past the 2nd row is allowed to break the octet rule and does not need to obey it. However, Rows 1 and 2 have to. Wait but isn’t boron one of the exceptions since it will usually have less than an octet and is in the second row? Yes boron is an exception...

Nick Pascua 2L

Hello and quick question,

I keep getting confused but is the formal charge the overall average of formal charges in a molecule or is it the sum of all formal charges in a molecule?

Thanks so much!

Nick Pascua 2L

Hello, I'm watching an Organic Chemistry Tutor Youtube video right now on how to draw on a phosphate ion (PO4^-3). He said it's best to avoid giving the central atom a negative formal charge by drawing bonds rather than keeping lone pairs, why is this a bad thing or why do we have to avoid this? Tha...

Nick Pascua 2L

Dispersion forces are found in all molecules whether it is ionic or covalent and are considered as the weakest type of intermolecular force. Electronegativity on the other hand is solely based on one molecule and how it attracts its atoms.

Nick Pascua 2L

Hello, When you said BF3, did you mean the BF3 molecule with a formal charge of 0? If so, then I believe it's actually more stable. I also believe it depends on which BF3 you're talking about to determine if it was less or more stable. BF3 also has another structure where it has a double bond connec...

Nick Pascua 2L

Hi!

I believe it is Euler's number although I might be wrong. I was looking at the example you said and did the calculation and it said e^-2= 0.14, in which if you type it in your calculator using Euler's number you'll get 0.1353 which is fairly close if you round. I hope that helps!

Nick Pascua 2L

Hi!

Yes, water is also a compound that shares the same characteristic of strong ionic character. This is due to the strong polar covalent ponds where the the atoms are unequally shared. For other compounds, however, they might differ based on their polar attraction.

Nick Pascua 2L

Hey!

I'm honestly behind on some lectures because I have 2 midterms this week so it's been really stressful. The quarter system is definitely something I'm not used to but it'll take some time! Good luck on midterms if you guys still have any!

Nick Pascua 2L

Hi!

I'm trying to wrap my head around this but I'm still kind of confused. But what's the difference between ionization energy and first ionization energy? Or is there a difference?

Thanks!

Nick Pascua 2L

Hi! So for any particle that is gravitationally or electrically bound (like an electron), it will have negative potential energy and needs some sort of positive work (like a photon) done on it. In the photoelectric effect, the positive work obviously has to be equal or have more energy than the nega...

Nick Pascua 2L

Hi! Ionization energy is the minimum amount of energy to remove a valence electron(s) from the outer shell of an atom (in which the maximum electrons that can be held in every shell is 8. For example, on the elements on the top right like Fluorine (7 valence electrons) and Oxygen (6 valence electron...

Nick Pascua 2L

Hello, Keep in mind that valence electrons only means the outer shell, and in your case it is only looking for the number of electrons on the outer shell given 5s2 and 5p3. Your electron configuration is correct, but count how many electrons are on the outer shell. The 5th orbital is what it is sayi...

Nick Pascua 2L

Hello, The (+) in Rb+ means that an electron is missing from the atom, to where there are more protons than electrons thus the atom has a positive charge. The bigger the positive charge, the smaller the radius will be and more electrons will be pulled tightly towards the nucleus. Since Rb+ has 1 les...

Nick Pascua 2L

Hello, I'm genuinely curious about this question related to light and I wanted to know if anyone has an answer to this. I understand that in order for an atom to produce light an electron is needed to return to a lower energy level. How does an atom continuously emit light for any given amount of ti...

Nick Pascua 2L

Hello!

Since it is telling you that the line is observed at the ultraviolet spectrum of the hydrogen atom, then it is in the Lyman series, which means that the n final will be n=1. Now we need to find the n initial.

To do this, we have to use the Rydberg formula to find n initial.

Nick Pascua 2L

Hi! Is the 15 you put 15M? Then if so, then yes I'd say it is pretty straightforward since you would be using M1V1=M2V2. You have your initial volume, initial molarity, and final molarity, so just solve for the final volume? For your second question, the c would stand for concentration while M (uppe...

Nick Pascua 2L

Hello, I believe if you use the equation E=hv and c=(lambda)v, then you can calculate E (which stands for the Energy per photon) by solving for v then using it in the E=hv equation. Since E stands for the Energy per photon, does it give you information about total energy (usually represented as a fo...

Nick Pascua 2L

Hi! With Heisenberg's equation to be ΔxΔp≥h/4Π, we are trying to solve for the velocity. Keep in mind that p= mass x velocity and that the mass of an electron is (9.11*10^-31 kg). To find the uncertainty of the position (Δx), we need to multiply the diameter of the hydrogen atom by the percent accur...

Nick Pascua 2L

Hello! Yes, even if electrons are excited and are at a higher energy, the atom will not emit light until they go from that higher energy level to a lower energy level. In terms of visibility, since we cannot see atoms through the human eye, this is why we use light-focusing microscopes that cause th...

Nick Pascua 2L

Hi! When two waves are in the same path, energy is always conserved and the end results will depend on the waves. For constructive waves, two waves will combine energies together usually because they are in phase (their crests line up), ultimately increasing the amplitude of the wave. The opposite w...

Nick Pascua 2L

Hi!

I would say that leaving it as "h" is fine as long as you make a side note on your paper showing what "h" is equal to. Then you can draw arrows pointing from the constant's value to where it is being applied to your work.

Hope that helps!

Nick Pascua 2L

Hi! So from our lecture with the example that Dr. Lavelle gave, just because a certain wavelength is being absorbed doesn't mean that there is a wavelength going to be emitted. If the wavelength does not have enough energy to release the electrons from a surface, then there won't be anything emitted...

Nick Pascua 2L

Hi! So to find Carbon, you would need to use the product of CO2 and perform reverse dimensional analysis. You would start with the grams of CO2, convert that to moles of CO2, convert to moles of C (in which there is 1 mole of C in CO2), then convert that into grams of C. Do this for both H and N. Wi...

Nick Pascua 2L

Hello! For a) consider the M1V1=M2V2 (Initial Molarity x Initial Volume = Final Molarity x Final Volume) equation. You are given your initial amounts of volume and molarity, as well as your final molarity. It is asking how you would prepare for this dilution, so you would need to calculate your fina...

Nick Pascua 2L

Hi! Someone had a similar question to this. When dealing with problems that give states of matter, it depends on the what is being asked. If you're told to provide an answer for a specific number (usually problems like molarity calculations), their states of matter doesn't really interfere with the ...

Nick Pascua 2L

Hi! So depending on the problem, you can manipulate with whatever you are given to help you solve it. Since I don't know your problem, are you familiar with the DMV Triangle or how density, mass, and volume all relate? If not, there are resources on the internet for you like the DMV Triangle. densit...

Nick Pascua 2L

Hi! So I had some trouble understanding the use of __ mol Rxn in stoichiometry. I noticed that in my TA's discussion section there was usually "1 mole of Rxn" used to convert something (I think it has something to do with the moles of the products in general?). I never learned this in high...

Search found 101 matches