Search found 97 matches
- Sun Feb 28, 2021 6:00 am
- Forum: Administrative Questions and Class Announcements
- Topic: LS7a
- Replies: 16
- Views: 1933
Re: LS7a
I took it with Maloy last quarter, and he was terrific! He was a super clear lecturer, and explained everything in a really accessible way. I retained practically zero information from my bio class and still did well. My main tips for this class are to really go over the practice exam questions on l...
- Sun Feb 28, 2021 5:41 am
- Forum: Student Social/Study Group
- Topic: Pre-Med Advice
- Replies: 6
- Views: 487
Re: Pre-Med Advice
viewtopic.php?f=157&t=21765
viewtopic.php?f=157&t=45665
There's some really great advice in these threads!
viewtopic.php?f=157&t=45665
There's some really great advice in these threads!
- Sun Feb 28, 2021 5:39 am
- Forum: Administrative Questions and Class Announcements
- Topic: summer session classes
- Replies: 17
- Views: 831
Re: summer session classes
Janna Shakiba wrote:Does anyone know if chem 14D is being offered this summer?
I don't think it will be.
- Sun Feb 28, 2021 5:38 am
- Forum: Student Social/Study Group
- Topic: Final
- Replies: 63
- Views: 3053
Re: Final
I'm going to go through all of the homework problems again and really note what kinds of mistakes I make.
- Sun Feb 21, 2021 2:15 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Can We Review our Exams?
- Replies: 69
- Views: 2937
Re: Can We Review our Exams?
Your TA can't show you the questions, but they read you the questions to you that you missed and go over them with you verbally
- Sun Feb 21, 2021 2:13 pm
- Forum: Student Social/Study Group
- Topic: Culinary Chemistry
- Replies: 239
- Views: 31814
Re: Culinary Chemistry
This is such a great thread! I love cooking and it's really cool to apply things I learned in chem class to my cooking :)
- Sun Feb 21, 2021 2:10 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Textbook Problems
- Replies: 8
- Views: 435
Re: Textbook Problems
Here's a link to the solution manual errors: I think it gets updated pretty regularly so it's good to have the newest versions
https://lavelle.chem.ucla.edu/wp-conten ... rs_7Ed.pdf
https://lavelle.chem.ucla.edu/wp-conten ... rs_7Ed.pdf
- Sun Feb 21, 2021 2:07 pm
- Forum: Administrative Questions and Class Announcements
- Topic: summer session classes
- Replies: 17
- Views: 831
Re: summer session classes
I did want to add that while saving a spot right now is probably a good idea, UCLA does charge you a $150 "processing fee" if you drop all of your summer session classes so make sure you are committed to taking at least 1 class over the summer. https://summer.ucla.edu/academiccourses/onlin...
- Sun Feb 21, 2021 1:54 pm
- Forum: Student Social/Study Group
- Topic: Preparing
- Replies: 24
- Views: 1141
Re: Preparing
Agree with everyone else who suggested YouTube lectures, those have always been super helpful for me when I need extra explanations on a confusing topic.
- Sun Feb 14, 2021 7:51 pm
- Forum: Student Social/Study Group
- Topic: Silly Mistakes?
- Replies: 72
- Views: 5803
Re: Silly Mistakes?
I totally need this :( This is how I felt about MT1 as well. Overall I thought I knew/ prepped the material well, but I made so many silly mistakes. I need to work on 1) Slowing down to read the question better and 2) Being more forgiving of myself. Thanks for posting this!
- Sun Feb 14, 2021 7:50 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm 2 Question #
- Replies: 5
- Views: 278
Re: Midterm 2 Question #
Don't think this info has been released yet, but I'm grateful for the 2 bonus questions on this midterm!
- Sun Feb 14, 2021 11:03 am
- Forum: Administrative Questions and Class Announcements
- Topic: Lecture #16 Error
- Replies: 6
- Views: 318
Re: Lecture #16 Error
This happens to me a lot. I usually just keep refreshing every now and then and it will eventually re-appear for me.
- Sun Feb 14, 2021 11:03 am
- Forum: Administrative Questions and Class Announcements
- Topic: Monday Holiday Workshops
- Replies: 3
- Views: 190
Re: Monday Holiday Workshops
Yes, there's 2 1-hour workshops on Monday (Jacqueline Jiang 12-1 PM/ Michelle Nguyen 1-2 PM)
- Thu Feb 11, 2021 6:19 am
- Forum: Administrative Questions and Class Announcements
- Topic: cc update
- Replies: 23
- Views: 1079
Re: cc update
My hasn't been updated either, but just wait it out :) They will definitely be updated eventually.
- Sun Feb 07, 2021 12:50 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Saping 3/4 #14
- Replies: 1
- Views: 129
Re: Saping 3/4 #14
For part A, you want to use the equation w = -n*R*T*ln(V2/V1). To do so, you will first need to find the number of moles n using the equation n = pV/RT (derived from the equation pV = nRT). Be sure to use the correct ideal gas constant (check your units). In this case, it would be R = 8.206 * 10^-2 ...
- Sun Feb 07, 2021 12:11 pm
- Forum: Student Social/Study Group
- Topic: Students Who Have a Job
- Replies: 103
- Views: 8988
Re: Students Who Have a Job
I'm starting a part-time job next quarter and will also be balancing classes, so this has been a helpful thread for me :) Feeling nervous, but hopefully I can pull it off...
- Sun Feb 07, 2021 12:06 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Translational, Rotational, Vibrational energy
- Replies: 2
- Views: 140
Re: Translational, Rotational, Vibrational energy
I don't think Dr. Lavelle would test us on topics we don't cover in class/ outlines/ hw
- Thu Feb 04, 2021 11:54 am
- Forum: Administrative Questions and Class Announcements
- Topic: Sapling Weeks 3,4,5 Grade Error
- Replies: 4
- Views: 270
Re: Sapling Weeks 3,4,5 Grade Error
Sometimes it takes awhile for my Sapling grade to update (it sometimes takes a day or so for me). I wouldn't be too worried about it.
- Wed Feb 03, 2021 6:33 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Tips for Concentrating during a test
- Replies: 31
- Views: 1150
Re: Tips for Concentrating during a test
I have the same problem!! It's really hard for me to have a quiet work environment during tests as there is always tons of noise in my house and the walls are super thin :( I try to tell people to leave me alone / be quiet during my exam times but invariable some always starts playing music/ talking...
- Wed Feb 03, 2021 6:24 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 14bl virtual or in person
- Replies: 13
- Views: 602
Re: 14bl virtual or in person
Here's a thread about virtual 14BL that I thought was helpful: viewtopic.php?f=160&t=73457&p=307581&sid=b5b694557f4c89a9b304f119a8da48db#p307581
- Sat Jan 30, 2021 5:24 am
- Forum: Administrative Questions and Class Announcements
- Topic: 14BL and CL
- Replies: 13
- Views: 665
Re: 14BL and CL
I would also like to know the answer to this! Building off of this, how many hours would you say that you spend on the labs (class time + assignments) each week?
- Thu Jan 28, 2021 7:37 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Textbook 4.31
- Replies: 4
- Views: 214
Re: Textbook 4.31
In my textbook it's written as C(s), graphite
- Thu Jan 28, 2021 6:24 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Textbook 4.31
- Replies: 4
- Views: 214
Re: Textbook 4.31
The enthalpy of formation of graphite C(s) is 0 kJ/mol. You can look up this value in Appendix 2 in the textbook.
- Wed Jan 27, 2021 1:39 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 4.31: Hess's Law vs. Bond Enthalpies
- Replies: 2
- Views: 153
4.31: Hess's Law vs. Bond Enthalpies
Screenshot 2021-01-27 162421.png When I first approached this question, I calculated the change in enthalpy using the sum of bond enthalpy changes. On the products side, we break two O-H bonds (2 * 463). On the reactants side, we form one H2 bond (-436) and one CO bond (-1074). Once I added these b...
- Tue Jan 26, 2021 5:30 pm
- Forum: Administrative Questions and Class Announcements
- Topic: posting screenshots
- Replies: 4
- Views: 520
Re: posting screenshots
Once you've dragged your screenshots into the window, you can click "place inline" at the bottom where it says "Attachments," and the image will appear in your text.
- Mon Jan 25, 2021 6:42 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Textbook 4D.21 c
- Replies: 1
- Views: 88
Re: Textbook 4D.21 c
I got the same answer as you, and looking at the solutions manual, I'm pretty sure there is either something wrong in the solutions manual or in Appendix 2A. The enthalpy of formation for K2S(aq) given in the Appendix 2 is -471.5 kJ/mol, but is given as -417.5 kJ/mol. So it just looks like a typo to...
- Mon Jan 25, 2021 6:39 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 4D.21 part C
- Replies: 4
- Views: 248
Re: 4D.21 part C
I'm pretty sure this is a solutions manual error. The enthalpy of formation for K2S(aq) given in the Appendix 2 is -471.5 kJ/mol. However, in the solutions manual it is given as -417.5 kJ/mol.
- Sat Jan 23, 2021 6:30 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm 1 Outline 3
- Replies: 3
- Views: 155
Re: Midterm 1 Outline 3
From his email on Friday: "Midterm 1 covers Chemical Equilibria, Acid and Base Equilibria, and only these Week 3 topics (4D.3; 4D.4; 4D.5; 4E.3)"
- Thu Jan 21, 2021 6:34 am
- Forum: Administrative Questions and Class Announcements
- Topic: Where to find textbook answers
- Replies: 4
- Views: 113
Re: Where to find textbook answers
Also sometimes the textbook solutions aren't entirely accurate --you can find some solution manual errors listed here: https://lavelle.chem.ucla.edu/wp-conten ... rs_7Ed.pdf
- Thu Jan 21, 2021 6:31 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Lower pkb is more basic
- Replies: 4
- Views: 628
Re: Lower pkb is more basic
Going off of that, pkb = -log(kb). Because it is a negative log value, lower values of pkb imply higher levels of kb. Likewise, because kb is a measure of dissociation of the base [B+][OH-]/[BOH], a higher kB means that more of the base has dissociated -> more basic. Thus, lower pkb values -> more b...
- Tue Jan 19, 2021 4:54 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Week 2 #5
- Replies: 4
- Views: 139
Re: Sapling Week 2 #5
You can start by using the pH to determine the pOH (pOH = 14-pH). With the pOH, you have the OH- concentration which is also the concentration that is protonated [BH+]. You would then divide this concentration [BH+] by ([BH+] + [B]) to solve for the percentage that is protonated. You can solve for [...
- Mon Jan 18, 2021 8:31 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook 6D.7
- Replies: 3
- Views: 168
Re: Textbook 6D.7
I'm not sure exactly why you are getting the answers that you have, but if you set the equation for part A as 3.0 x 10^-8 = (2.512 x 10^-5)^2 / (x - 2.512 x 10^-5) Since 3.0 x 10^-8 is a very small number, you can approximate this as 3.0 x 10^-8 = (2.512 x 10^-5)^2 / X Solving for X would result in ...
- Fri Jan 15, 2021 11:27 am
- Forum: Administrative Questions and Class Announcements
- Topic: Winter 2021 Midterm Dates
- Replies: 2
- Views: 95
- Thu Jan 14, 2021 7:31 am
- Forum: Student Social/Study Group
- Topic: New Joke Chain
- Replies: 46
- Views: 2859
Re: New Joke Chain
Nick P 3D wrote:H2O is water and H2O2 is hydrogen peroxide.
What is H2O4?
Drinking
Can someone explain this joke? I don't get it :(
Same with this from lecture yesterday:
- Thu Jan 14, 2021 7:13 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Homework problem 6B.9
- Replies: 3
- Views: 197
Re: Homework problem 6B.9
Dr. Lavelle said that there was a typo in this question, and we shouldn't do it. See the solutions manual errors PDF: https://lavelle.chem.ucla.edu/wp-conten ... rs_7Ed.pdf
- Wed Jan 13, 2021 6:01 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Temperature & K for Acids and Bases
- Replies: 4
- Views: 207
Re: Temperature & K for Acids and Bases
I'm not sure what you mean by "does the 25 degrees Celsius always hold for strong acid or base reactions," but the values of K do depend on temperature. If you are asking whether temperature influences whether the reaction contains a strong acid or base, it doesn't.
- Tue Jan 12, 2021 3:13 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling 5
- Replies: 4
- Views: 186
Re: Sapling 5
Think about how you would manipulate the given equations to arrive at 2NH3(g)+3I2(g)↽−−⇀N2(g)+6HI(g) You could start by looking for the first term in the above equation, 2NH3, in one of the given equations. Notice that the given equation N2(g)+3H2(g)↽−−⇀2NH3(g) contains 2NH3, and you can get 2NH3 on...
- Fri Jan 08, 2021 7:40 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Focus Exercise 5.39 Question
- Replies: 2
- Views: 140
Re: Focus Exercise 5.39 Question
I was also confused about this question... could someone clarify? My guess is there is an error for the Kc value that's not noted in the solutions manual error? Also my textbook says "In Table 5E.2..." which I'm pretty sure is a mistake because I don't think "Table 5E.2" exists. ...
- Fri Jan 08, 2021 7:02 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chemical Equilibrium_Textbook Problem_5G.5
- Replies: 3
- Views: 102
Re: Chemical Equilibrium_Textbook Problem_5G.5
NP! I'm really curious as to how to answer this question now... Does anyone have an idea of how to approach part a? How can we tell which is at equilibrium with out knowing Kc/ equilibrium equation?
- Wed Jan 06, 2021 7:43 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: adding chemical equations
- Replies: 2
- Views: 137
Re: adding chemical equations
You can refer to table 5G.2 to see how you might arrive at the equation you are trying to solve the K for through any combination of reactions listed in Table 5G.2. You may have to manipulate the equations in this table to get at your equation such as reverse the reactions, changing the coefficients...
- Wed Jan 06, 2021 7:21 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Concept Clarification About Equilibrium Constants
- Replies: 3
- Views: 139
Re: Concept Clarification About Equilibrium Constants
We want the equilibrium constant K to be unitless. Dividing by standard pressure cancels out the units (bar) in each term so that we end up with a unitless K.
- Wed Jan 06, 2021 7:15 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chemical Equilibrium_Textbook Problem_5G.5
- Replies: 3
- Views: 102
Re: Chemical Equilibrium_Textbook Problem_5G3
I'm not really sure how to approach this question either so I would also like to hear if anyone has an idea (how can we tell which flask is at equilibrium without having the reaction equation /knowing the concentrations at equilibrium?). However, I did want to say that I think you are looking at pro...
- Wed Jan 06, 2021 7:07 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Forward vs Reverse Reactions
- Replies: 3
- Views: 157
Re: Forward vs Reverse Reactions
My understanding is that when you add more reactant to an reaction that is already at equilibrium, the reaction shifts to the right (forward reaction) and more product is produced, allowing the reaction to regain equilibrium. However, when you add more product to an equation that is already at equil...
- Sat Dec 12, 2020 7:02 am
- Forum: Lewis Acids & Bases
- Topic: Conjugate base of Boric Acid (6.13)
- Replies: 1
- Views: 205
Conjugate base of Boric Acid (6.13)
Could someone explain to me why the conjugate base of Boric acid has an added OH pairing, rather than removing an H (donating a proton)?
- Fri Dec 11, 2020 4:34 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: formic and acetic acid
- Replies: 4
- Views: 218
Re: formic and acetic acid
How do we know that the CH3 in acetic acid is electron donating?
- Wed Dec 09, 2020 12:34 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Lecture Videos Not Playing [ENDORSED]
- Replies: 16
- Views: 670
Re: Lecture Videos Not Playing [ENDORSED]
I've been experiencing the same issue. However, I just tried the second video (Play 2) and it seems to be working (for both Monday 12/7 and 12/9 lectures)! -Matt I've been trying Play 2 but unfortunately it hasn't been working for me either. For some confusing reason the videos work at certain time...
- Wed Dec 09, 2020 12:33 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Lecture Videos Not Playing [ENDORSED]
- Replies: 16
- Views: 670
Re: Lecture Videos Not Playing [ENDORSED]
TJ Lai 2K wrote:Not sure if this will work for everyone, but it's working for me now with the Cisco UCLA VPN turned on.
Nvm it stopped working for me again :(
- Wed Dec 09, 2020 12:19 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Lecture Videos Not Playing [ENDORSED]
- Replies: 16
- Views: 670
Re: Lecture Videos Not Playing [ENDORSED]
Not sure if this will work for everyone, but it's working for me now with the Cisco UCLA VPN turned on.
- Wed Dec 09, 2020 10:52 am
- Forum: Administrative Questions and Class Announcements
- Topic: Lecture Videos Not Playing [ENDORSED]
- Replies: 16
- Views: 670
Re: Lecture Videos Not Playing [ENDORSED]
I am having this error too... tried switching to a different browser but nothing has worked. Has anyone figured out a way to fix this?
- Wed Dec 09, 2020 9:43 am
- Forum: Significant Figures
- Topic: 12/07 Lecture sig figs
- Replies: 4
- Views: 373
12/07 Lecture sig figs
Screenshot 2020-12-09 122729.png During Monday's lecture Dr. Lavelle, said that the sig figs for the answer to the above question is equal to the number of figures after the decimal point of 4.22 (2 sig figs), resulting in the answer 6.0 * 10^-5. I had thought that the number of sig figs for 4.22 i...
- Mon Dec 07, 2020 8:52 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Topic 9C Exercises Question 5
- Replies: 7
- Views: 290
Re: Topic 9C Exercises Question 5
You can usually tell if something is polydentate if the atom follows the structure Lone pair - spacer - spacer- lone pair. So for example in ox, it has an oxygen with a lone pair carbon as a spacer another carbon as a spacer and then another oxygen with a lone pair. It also has a single bond betwee...
- Mon Dec 07, 2020 8:51 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Course Evaluations
- Replies: 10
- Views: 500
Re: Course Evaluations
Dr. Lavelle hasn't said anything about us getting points or extra credit for completing the UCLA course evaluations or the Sapling evaluation. What is the Sapling evaluation? I think this is referring to the survey about the Chemical Principles textbook that Dr. Lavelle sent in an email last Tuesday.
- Sun Dec 06, 2020 8:07 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Topic 9C Exercises Question 5
- Replies: 7
- Views: 290
Re: Topic 9C Exercises Question 5
You can usually tell if something is polydentate if the atom follows the structure Lone pair - spacer - spacer- lone pair. So for example in ox, it has an oxygen with a lone pair carbon as a spacer another carbon as a spacer and then another oxygen with a lone pair. It also has a single bond betwee...
- Wed Dec 02, 2020 9:26 am
- Forum: Hybridization
- Topic: Question 2F.15
- Replies: 6
- Views: 335
Re: Question 2F.15
Could someone explain under what circumstances the degree of contribution that a certain orbital (s, p, etc. would increase)? In other words, what would determine the degree of s-character?
- Wed Dec 02, 2020 8:13 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Textbook Problem 2E #13
- Replies: 3
- Views: 198
Re: Textbook Problem 2E #13
I agree that there might be an issue with your textbook. Here's what the answer key looks like for that question for me.
- Wed Dec 02, 2020 8:04 am
- Forum: Lewis Structures
- Topic: Varying Arrangements of Structure
- Replies: 5
- Views: 271
Re: Varying Arrangements of Structure
For CH 2 Cl 2 there is no change in the VSEPR structure, but there is also no difference in the polarity of the molecule, right? Regardless of where the chlorine atoms are placed around the central carbon, the molecule has the same polarity. Is this correct? I believe so, yes. CH 2 Cl 2 has a tetra...
- Wed Dec 02, 2020 7:45 am
- Forum: Hybridization
- Topic: Textbook Q 2F #7
- Replies: 4
- Views: 306
Re: Textbook Q 2F #7
IMG_20201202_104500~2.jpg Here's how I drew the Lewis structure. The lone pair, as well as the bonding pairs, all "count" with regards to hybridization, so in this case AsF3 has 4 groups that count towards hybridization -> sp3 Here's a really quick and helpful video that I've used that ex...
- Sat Nov 28, 2020 8:05 pm
- Forum: Octet Exceptions
- Topic: Expanded Octet Question
- Replies: 8
- Views: 702
Re: Expanded Octet Question
^^^ I think Beryllium, Boron, Aluminum tend to have incomplete (not expanded) octets
this was a helpful resource for me: https://courses.lumenlearning.com/chemi ... ctet-rule/
this was a helpful resource for me: https://courses.lumenlearning.com/chemi ... ctet-rule/
- Sat Nov 28, 2020 7:59 pm
- Forum: General Science Questions
- Topic: Grade Breakdown
- Replies: 35
- Views: 2142
Re: Grade Breakdown
I don't think he mentions anything on this, but he does say 50% or higher is required to pass with a C- or higher. I saw that too and was so confused... He is saying if you earn a 50% in the class you automatically pass? yep I think to pass the class with a C- or higher you'll need at least a 50% i...
- Sat Nov 28, 2020 7:52 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 14B vs 14A
- Replies: 12
- Views: 628
Re: 14B vs 14A
I think 14B will be asynchronous, similar to 14A
- Sat Nov 28, 2020 7:48 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Dr. Lavelle's Email
- Replies: 3
- Views: 244
Re: Dr. Lavelle's Email
I've emailed Dr. Lavelle before and he was very prompt at responding! So definitely try that if you're not able to attend / get his attention during office hours (I know there are often lots of other students there).
- Mon Nov 23, 2020 9:14 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Why are hydrogen bonds so strong relative to other dipole-dipole bonds?
- Replies: 11
- Views: 13520
Re: Why are hydrogen bonds so strong relative to other dipole-dipole bonds?
Thanks for everyone's responses! I still don't really understand why hydrogen bonds are unique in that they are so much stronger relative to other dipole-dipole bonds (-20 kJ/mol vs. -2 kJ/mol). It doesn't totally make sense to me that hydrogen bonds are 10X stronger than other dipole-dipole bonds o...
- Sat Nov 21, 2020 4:29 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: chemical formula of compound
- Replies: 6
- Views: 282
Re: chemical formula of compound
Can someone explain aluminum hydride to me? I know the answer is AlH3, but I'm confused as to how the +3 ionic charge for aluminum balances the +1 ionic charge for hydrogen. Al has a charge of +3 and H has a charge +1, so in order to create the compound, you are basically just swapping the charges ...
- Sat Nov 21, 2020 4:28 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Why are hydrogen bonds so strong relative to other dipole-dipole bonds?
- Replies: 11
- Views: 13520
Why are hydrogen bonds so strong relative to other dipole-dipole bonds?
Why are hydrogen bonds uniquely strong among dipole-dipole forces? For example, why are dipole-dipole bonds involving H so much stronger compared to dipole-dipole bonds involving an element that is even less electronegative, such as Si, or approximately the same electronegativity, such as P? Also, w...
- Sat Nov 21, 2020 3:35 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 14B and 14BL
- Replies: 13
- Views: 786
Re: 14B and 14BL
Does anyone have an idea of what 14BL will be like over Zoom?
- Thu Nov 19, 2020 11:13 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: chemical formula of compound
- Replies: 6
- Views: 282
Re: chemical formula of compound
Can someone explain aluminum hydride to me? I know the answer is AlH3, but I'm confused as to how the +3 ionic charge for aluminum balances the +1 ionic charge for hydrogen.
- Tue Nov 17, 2020 6:04 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionization energy
- Replies: 4
- Views: 1505
Re: Ionization energy
Following the logic that Na becomes very stable after losing 1 electron as it attains noble gas configuration, can we also say that Na has higher 2nd ionization energy relative to Al?
- Sat Nov 14, 2020 2:30 pm
- Forum: Dipole Moments
- Topic: Sapling #19
- Replies: 12
- Views: 538
Re: Sapling #19
I just saw that Dr. Lavelle responded to another post about this and said that H2S was a mistake (meant to say SO2).
- Sat Nov 14, 2020 2:21 pm
- Forum: Dipole Moments
- Topic: Sapling #17
- Replies: 8
- Views: 4014
Re: Sapling #17
FionaHunter21 wrote:Are london dispersion forces present in all nonpolar molecules?
London dispersion forces are present in all molecules, but they are the only intermolecular force present in nonpolar molecues.
- Sat Nov 14, 2020 2:19 pm
- Forum: Dipole Moments
- Topic: Week 5/6 Sapling Question
- Replies: 4
- Views: 480
Re: Week 5/6 Sapling Question
Each of the (slightly positive) H atoms can form a hydrogen bond with the slightly negative charge in the O atom of an H2O molecule. +4 hydrogen bonds Likewise, each of the (slightly negative) N atoms can form a hydrogen bond with the slightly negative positive charge in the H atom of an H2O molecul...
- Sat Nov 14, 2020 1:45 pm
- Forum: Dipole Moments
- Topic: Sapling Question #13
- Replies: 5
- Views: 170
Re: Sapling Question #13
So other hydrogen atoms can form hydrogen bonds to any N,O, or F molecule that has unpaired electrons in the valence shell? Or do they need to be N,O, and F atoms that are already bonded with a hydrogen? The way I understand it, the hydrogen atom must be covalently bonded to an electronegative atom...
- Sat Nov 14, 2020 1:38 pm
- Forum: Dipole Moments
- Topic: Sapling #19
- Replies: 12
- Views: 538
Re: Sapling #19
I said dipole-dipole, because O is more electronegative than S and the partially positive (S) and partially negative (O) areas of each molecule are attracted to each other. Not sure why it says H2S or that H2S is polar (I think it meant to say SO2).
- Sun Nov 08, 2020 3:24 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Posting Screenshots on Chem Community
- Replies: 3
- Views: 121
Re: Posting Screenshots on Chem Community
I just tried it, and basically I saved the screenshot, dragged it into the textbox, and then at the bottom where it says "Attachments," I clicked "place inline."
- Sun Nov 08, 2020 3:20 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Question for Students about High School Chem
- Replies: 25
- Views: 856
Re: Question for Students about High School Chem
I really, really appreciate that Dr. Lavelle starts every section off with fundamentals! I never took AP Chem and retained essentially zero chemistry from high school, but I've found this class to still be pretty manageable even with basically no chem background.
- Sun Nov 08, 2020 3:16 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chem 14B Enrollment
- Replies: 27
- Views: 1628
Re: Chem 14B Enrollment
BoparaiAdeshsurjit2I wrote:Will Chem 14B also have asynchronous lectures?
I think it will, just like 14A
- Sun Nov 08, 2020 3:13 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Taking Bio and Chem simultaneously
- Replies: 26
- Views: 2169
Re: Taking Bio and Chem simultaneously
I'm taking the LS7A along with Chem14A right now. It's not too bad of a combination, but I've found LS7A to be more time-consuming than Chem (it takes me longer to memorize/understand the concepts). I retained basically zero information from high school biology and chemistry though, so if you still ...
- Sun Nov 08, 2020 3:08 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chem 14BL?
- Replies: 7
- Views: 355
Re: Chem 14BL?
Does anyone know what BL looks like as an online class? Will there be lab demonstrations over Zoom?
- Sat Oct 31, 2020 2:22 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chemistry Modules
- Replies: 7
- Views: 277
Re: Chemistry Modules
I found them to be super helpful too, so I'm kinda sad that there won't be more modules for the rest of the material (but totally understandable given how much work is put into running the class already). Hopefully for future years Dr. Lavelle can use the class recordings from this quarter!
- Sat Oct 31, 2020 2:19 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Scores
- Replies: 4
- Views: 136
Re: Midterm Scores
I think Dr. Lavelle said that one of the midterm questions had an error so they will have to go through each midterm individually, which will take some time.
- Fri Oct 30, 2020 7:11 am
- Forum: Significant Figures
- Topic: Sig Figs for electron shells
- Replies: 4
- Views: 257
Sig Figs for electron shells
For electron shells, can we assume that each quantity has "infinite" sig figs (e.g. 2.000000...) because we know that shells can only be whole numbers? So in a problem, we should base the number of sig figs off of the value we are given for the wavelength/ frequency etc.?
- Thu Oct 29, 2020 9:36 am
- Forum: Molarity, Solutions, Dilutions
- Topic: Fundamentals G21
- Replies: 3
- Views: 225
Fundamentals G21
Hi everyone, G21 asks us to find the molarity of potassium and sulfide ions in a solution is prepared by dissolving 0.500 g of KCl, 0.500 g of K2S, and 0.500 g of K3PO4 in 500 mL of water. I know the molarity equation is (moles of solute) / (volume of solution). For this problem, shouldn't the volum...
- Thu Oct 29, 2020 5:55 am
- Forum: Administrative Questions and Class Announcements
- Topic: Sapling Access Code
- Replies: 5
- Views: 285
Re: Sapling Access Code
I would send another email to the UCLA store, or call them if possible. Be persistent and I'm sure it will be fine :)
- Sun Oct 25, 2020 9:09 am
- Forum: Properties of Light
- Topic: Emission/Absorption
- Replies: 6
- Views: 270
Re: Emission/Absorption
I think for frequency and wavelength, we basically take the absolute values of the result because we know that frequency and wavelength can never be negative. I agree with Aaron that n1 and n2 should be thought of as n_final and n_initial (not just that the lower value has to be n1 and the higher va...
- Sun Oct 25, 2020 8:48 am
- Forum: Administrative Questions and Class Announcements
- Topic: Schrodingers/Orbitals on Midterm?
- Replies: 2
- Views: 108
Re: Schrodingers/Orbitals on Midterm?
I think the main thing to know is that, conceptually, we can solve for the wavefunction using Schrodinger's equation and the square of the wavefunction is proportional to the probability density for where a particle could be in a region.
- Sun Oct 25, 2020 8:42 am
- Forum: Administrative Questions and Class Announcements
- Topic: Printouts for Midterm
- Replies: 8
- Views: 337
Re: Printouts for Midterm
Here are the printouts Dr. Lavelle provided:
Periodic table:
https://lavelle.chem.ucla.edu/wp-conten ... _IUPAC.pdf
Equations and constants:
https://lavelle.chem.ucla.edu/wp-conten ... ations.pdf
Periodic table:
https://lavelle.chem.ucla.edu/wp-conten ... _IUPAC.pdf
Equations and constants:
https://lavelle.chem.ucla.edu/wp-conten ... ations.pdf
- Sat Oct 24, 2020 8:10 am
- Forum: Administrative Questions and Class Announcements
- Topic: Memorize electromagnetic spectrum for midterm?
- Replies: 7
- Views: 298
Memorize electromagnetic spectrum for midterm?
Does anyone know if we should memorize the electromagnetic spectrum for the midterm? For example, now that visible light has wavelengths between 400 and 700 nm, etc. Thanks!
- Sat Oct 24, 2020 8:00 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Atomic Spectra Post Mod Q
- Replies: 3
- Views: 178
Re: Atomic Spectra Post Mod Q
I was torn between the choices, "Yes, because each molecule has a unique spectral pattern or fingerprint" and "Yes, because most molecule have a common spectral pattern or fingerprint." Is it the case that every molecule has a unique spectral fingerprint? Or can molecular spectro...
- Sun Oct 18, 2020 6:54 pm
- Forum: Photoelectric Effect
- Topic: Textbook Question 1A.11
- Replies: 3
- Views: 216
Re: Textbook Question 1A.11
Also, the Balmer and Lyman series refer to different "types" of spectral lines (Balmer series refers to spectral lines for visible light, Lyman series for UV)
- Sun Oct 18, 2020 6:42 pm
- Forum: Properties of Electrons
- Topic: Electron Wave-Particle Duality
- Replies: 10
- Views: 313
Re: Electron Wave-Particle Duality
Adam, here's a diagram that captures wavelength vs. frequency vs. amplitude.
The energy of each photon is equal to the Planck's constant * frequency
The energy of each photon is equal to the Planck's constant * frequency
- Sun Oct 18, 2020 6:25 pm
- Forum: Properties of Light
- Topic: Sapling homework question 5
- Replies: 3
- Views: 87
Re: Sapling homework question 5
First, I calculated frequency using the equation c = Wavelength * Frequency Remember that c is a constant equal to 3.00 * 10^8 m/s and the wavelength is given as 9.23×10−4 cm After solving for the frequency, plug that into the equation E = h * Frequency to solve for the Energy per photon Remember th...
- Sun Oct 18, 2020 6:13 pm
- Forum: Properties of Light
- Topic: Study Advice
- Replies: 50
- Views: 2084
Re: Study Advice
I've found doing the optional book problems to be really helpful for me in terms of understanding the material. I like that the Answer Key goes through each question very clearly and systematically.
- Sun Oct 18, 2020 6:10 pm
- Forum: Administrative Questions and Class Announcements
- Topic: UCLA Store Updates on Ebook/Sapling access card
- Replies: 16
- Views: 611
Re: UCLA Store Updates on Ebook/Sapling access card
I ordered mine 3 weeks ago or so but never received it in the mail. However, I did get an email from textonline@asucla.ucla.edu with my code (I never requested it, they somehow just knew to email it to me)...
- Fri Oct 09, 2020 7:48 pm
- Forum: Significant Figures
- Topic: How to deal with significant figures in decimals with zeros.
- Replies: 20
- Views: 1125
- Fri Oct 09, 2020 7:39 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Turning in textbook problems
- Replies: 10
- Views: 272
Re: Turning in textbook problems
I would definitely do some textbook problems (even if they're not graded for credit) as the prof. says that some of the questions from the exams will be taken from the textbook.
- Fri Oct 09, 2020 7:28 pm
- Forum: Limiting Reactant Calculations
- Topic: Sapling HW Week 1 Q10
- Replies: 4
- Views: 164
Re: Sapling HW Week 1 Q10
I was also confused about what happens to the Br and Mg. I just assumed that they weren't shown in the product because they weren't important to the question, but that the final product actually looks something like C7H16O + MgBr (which I'm pretty sure isn't an actual compound, so maybe equation in ...
- Fri Oct 09, 2020 7:10 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Exam Regulations
- Replies: 7
- Views: 186
Re: Exam Regulations
I'm pretty sure it will be closed book/ notes. We will also be installing Respondus which (I believe) monitors your browser activity during the exam.
- Fri Oct 09, 2020 7:06 pm
- Forum: Limiting Reactant Calculations
- Topic: Week 1 Sapling Q. 10
- Replies: 5
- Views: 411
Re: Week 1 Sapling Q. 10
Here's a picture of how I determined the molecular formulas based off of the diagrams