CHEMISTRY COMMUNITY

cadytran1K

I also can't figure out the second part of this problem! I can't seem to figure out what I'm doing wrong.

cadytran1K

I'm having a hard time with the last part of this problem: Calculate the equilibrium concentrations of N2O4 and NO2 after the extra 1.00 mol NO2 is added to 1.00 L of solution. [N2O4]= [NO2]= The Kc that I calculated is 11.2. I think my problem is solving for x. I set the equation up: [NO2]^2 / [N2O...

cadytran1K

Hi! I'm having trouble solving this problem and keep getting the wrong answer. At a certain temperature, the given reaction has an equilibrium constant of Kp=359 . PCl3(g)+Cl2(g)↽−−⇀PCl5(g) PCl5 is placed in a sealed container at an initial pressure of 0.0370 bar . What is the total pressure at equi...

cadytran1K

Mitzy Garcia 1k wrote:Yes, use the ICE table. I converted the units for SO3 and O2. I did this by using mol and L to equal to M. I hope that helps.

This is very helpful!! Thank you (:

cadytran1K

I believe you would be able to use the ICE table for both concentration and partial pressures! This is a great tool to keep everything organized.

cadytran1K

At a certain temperature, 0.860 mol SO3 is placed in a 4.00 L container.

2SO3(g)↽−−⇀2SO2(g)+O2(g)

At equilibrium, 0.180 mol O2 is present. Calculate Kc.

I'm having a little bit of trouble for this question. Would I just start by creating an ICE table?

cadytran1K

Last quarter, my TA said we were fine using any calculator, so I'm assuming it's the same this quarter.

cadytran1K

I believe it should be Units 1, 2 and maybe some of 3.

cadytran1K

It really depends on what you prefer! Last quarter I attended more sessions before/during midterms or finals week to prepare. That helped a lot for review and practice.

cadytran1K

Attending the UA sessions were really helpful! I would say going to as many of those as you can and also completing textbook problems because the exam questions are very similar to the homework. Also! I found watching videos from Organic Chemistry Tutor really helpful as well! Hope this helps.

cadytran1K

For me, I go off the name of the compound. Acids usually have a H at the beginning of the name, so I typically identify the acids first and then go off from there.

cadytran1K

Bond angles for T shapes are a little less than or equal to 90 degrees!

cadytran1K

In Dr.Lavelle's lectures, I remember him mentioning that we'll be going further into acids and bases in Chem 14B.

cadytran1K

Grades should be out Saturday! And I believe that you have until 10am Thursday now to get 50 chem community posts.

cadytran1K

I've been referring to Organic Chemistry Tutor and they've really helped me improve a lot!!

cadytran1K

If there's a topic I'm struggling on, I like to do practice problems (or hw problems) until I'm confident that I know what I'm doing. Organic Chemistry Tutor on YouTube is also a great resource!

cadytran1K

If you're international, there's also a time for 8pm - 9:30pm.

cadytran1K

I'm going to be going through the textbook problems and also attending the UA zoom sessions, as doing that has worked best so far in improving my grade.

cadytran1K

I'm honestly curious about this as well! As far as I know, and like everyone else has said, 50% is needed to pass with a C. I think the most important thing is to get enough points as you can.

cadytran1K

Hi! What has worked for me is referring to my periodic table. I know that elements that are closer to each other on the periodic table are ionic and elements further away are covalent. Hope this helps!

cadytran1K

I determine how many sigma and pi bonds are in a molecule based on the structure! There is one sigma bond present in every double bond and single bond while pi bonds are found in double and triple bonds. For instance, if there was a triple bond, there would be one sigma bond and two pi bonds. I hope...

cadytran1K

For me, I review sapling and also do the textbook problems as practice. Because Dr. Lavelle takes textbook problems for the test, I find this really helpful since the questions are similar. This helped me do a lot better on the second midterm.

cadytran1K

Sapling is set up so that if you give up on a question, it makes you lose points. Try doing as many attempts as you can because you get an unlimited number of attempts!

cadytran1K

I believe they will be covered before the final since we'll be examined on all of the material.

cadytran1K

I felt the same way the first midterm so I totally understand. Just remember that there are a lot of points you can earn in addition to the midterm! Rooting for you (:

cadytran1K

I'm assuming they will come out later this week. (:

cadytran1K

Hello! I was completing the text book problems and got a bit confused when asked to arrange cations from increasing polarizing power and anions from increasing polarizability. I mixed the two up at first. What is the difference between polarizing power and polarizability?

Thank you!

cadytran1K

In preparation for the midterm, should we be focusing on textbook problems 1D, 1E, 1F and all of outline 3 textbook problems?

cadytran1K

Hi! It's true that the 4d subshell has 5 orbitals (-2, -1, 0, +1, +2). However, this information only fits with n = 4 and l = 2. The question adds on that the magnetic quantum number must be -2. This refers to only one of the 5 orbitals (the one marked -2), so the answer is one orbital (only one or...

cadytran1K

Jasmine Yi 1H wrote:
cady_tran_2G wrote:I believe so! I might be wrong but I think Midterm 2 should cover the last of outline 2 and some of outline 3.

does this mean that Midterm2 doesn't cover all of outline 3?

It covers up to the lecture we had on 11/11.

cadytran1K

How many orbitals can have the following quantum numbers in an atom: (b) n=4, l=2, $m_{l}$ = -2

Hi! I'm studying for the midterm and I'm confused as to why when:
n = 4,
l = 2,
$m_{l}$ = -2

The number of orbitals is 1. Shouldn't it be 5 orbitals because the atom is at the 4d state?

cadytran1K

I have the same concerns as you did since I didn't do as well as I would have hoped for the first midterm. Hopefully the next midterm and final makes up for it!

cadytran1K

I agree with Audrey. This is a really good video that helped me understand this electron configuration exceptions: https://youtu.be/Ur2PuzJ7KWs

Hope this helps!

cadytran1K

I believe that Wednesday was the last lecture that covers material on the midterm. Just note that for midterm 2, it's going to cover the last 8 points of outline 2 and all of outline 3!

cadytran1K

Midterm 2 should cover the last 8 points on outline 2 and everything in outline 3.

cadytran1K

I'm also considering taking 14B and 14BL together but it honestly depends on what you prefer. I feel like it would be a good to take them during winter quarter, but you also have to consider how many classes you plan to take overall and if this is going to significantly affect your workload. I hope ...

cadytran1K

Like everyone said previously, writing things down helps me memorize things but also going through Quizlet flashcards really helps as well!

cadytran1K

This week's homework is due on Sunday of week 6. (:

cadytran1K

Hello! I might have missed this in the lecture, but when you're drawing a Lewis Structure, how do you identify whether or not an element is octet?

cadytran1K

Dr. Lavelle hasn't specified yet, but I'm assuming the last bullets of outline 2 and some of outline 3. Hope this helps!

cadytran1K

I believe so! I might be wrong but I think Midterm 2 should cover the last of outline 2 and some of outline 3.

cadytran1K

I know a few people have had this problem and they've all emailed the UCLA store, as Tianjian suggested. I think that would be the best solution to get your code ASAP.

cadytran1K

When I refer to velocity, I know that it is the standard, "v" but when I'm doing an equation that involves frequency, I know that the font for "v" is different.

cadytran1K

I'm also unsure! But as everyone has said, there was an error so I'm sure the TA's will have them all reviewed by the upcoming week or so. Hopefully soon!

cadytran1K

Hi! I'm a bit lost on how to solve problem 31) on the post assessment. The problem is:

A. If 3.607 x 10-19 J is required to remove an electron with zero kinetic energy from a metal surface, what would be the longest wavelength light that could do this?

cadytran1K

Hi! I agree with Justin. From the previous lectures, Dr. Lavelle mentioned that anything after 10^-15 would be observable. Anything under that would not be. Hope this helps!

cadytran1K

My TA said that the midterm is probably going to be similar to the post module assessments and that doing the assessments up to quantum world would be a great tool for studying. Hope this helps!

cadytran1K

I think nf and ni is the same as n1 and n2, but to be safe, I would also stick to using n1 and n2.

cadytran1K

Hi! The question is: When a metal was exposed to photons at a frequency of 1.00×1015 s−1, electrons were emitted with a maximum kinetic energy of 3.90×10^−19 J. Calculate the work function, Φ, of this metal. What is the maximum number of electrons that could be ejected from this metal by a burst of ...

cadytran1K

Like everyone said, this is false. I was confused about this too, but from what I gathered, a higher intensity doesn't increase the energy, it just increases the number of photons. The photoelectric effects states that if the energy of the photon is greater or equal to the energy to remove an electr...

cadytran1K

Hi! You should use meters because when you calculate the equations, the units will cancel out so you're left with meters. If the question asks you for the answer in nm, you would then convert m to nm.

cadytran1K

It definitely depends on the question, but if it doesn't specifically state what units to use, I think it would be okay to stick with meters.

cadytran1K

Hi! In the lecture, Dr. Lavelle mentioned that high intensity light would not emit electrons, but higher frequency light would. What's the difference between frequency and intensity?

cadytran1K

Hi! I'm not sure if this will be much help, but in my notes I wrote that even though there is high intensity light, the energy of the light has to be equal to or larger than the energy to remove in order for the electrons to be emitted. Also, if the intensity increases, the number of photons double....

cadytran1K

Hi! Like the previous reply, we're going to be tested on content and I remember Dr. Lavelle mentioning we'd be provided with compounds on a test.

cadytran1K

Hello! I know my TA mentioned that it would be better to show your work and be as precise as possible. Even though it's not required, it's always best to do so.

cadytran1K

I remember seeing on the syllabus that everything would be closed book.

cadytran1K

What I did was I determined the molecular formulas by counting up the number of carbon and hydrogens. This is a really good reference video if you can't remember: https://youtu.be/FbaXQ8u6IP8

From there, I calculated the molar mass.

cadytran1K

Hi Cady! You can look at the periodic table to see that the ion of Mg has a charge of +2 because of its 2 valence electrons, and the polyatomic ion sulfate is SO4 with a charge of -2. This means that MgSO4 is magnesium sulfate. Magnesium sulfate heptahydrate is MgSO4 plus 7H2O because hydrate repre...

cadytran1K

Epsom salts consist of magnesium sulfate heptahydrate. Write its formula. (a) How many atoms of oxygen are in 5.15 g of Epsom salts? (b) How many formula units of the compound are present in 5.15 g? (c) How many moles of water molecules are in 5.15 g of Epsom salts? In order to start the problem, I ...

cadytran1K

I interpret that by having until Sunday to post but I'm not really sure!

cadytran1K

For this problem, I would start by creating an equation: (1.345 mol/1000 mL) = (x mol/12.56 mL). "x" should give you the amount of moles in the 12.56 mL that has just been taken out. Once you've done that, you just divide the amount of moles you got by 250.0 mL since that is the volume tha...

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