Search found 137 matches

by Rebecca Remple 1C
Sat Mar 14, 2020 5:53 pm
Forum: General Science Questions
Topic: Chemistry Final
Replies: 16
Views: 276

Re: Chemistry Final

SarahCoufal_1k wrote:Also, will he be posting the link to his chem 14B website?

Hi Sarah,

You can access the final by logging into the home page of CCLE! :)

-Rebecca
by Rebecca Remple 1C
Sat Mar 14, 2020 12:45 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow Step on Reaction Profile (Endgame 14g)
Replies: 1
Views: 34

Slow Step on Reaction Profile (Endgame 14g)

Hi all, I am trying to understand problem 14g on Lyndon's worksheet, "Endgame". This problem asks us to draw a reaction profile given the reaction mechanism: Step 1: A+B->C+D Step 2: C+D+E->F+G+B The problem states that the reaction is exothermic. The reaction profile has two peaks, as exp...
by Rebecca Remple 1C
Sat Mar 14, 2020 8:08 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalyst's effect on overall reaction
Replies: 7
Views: 50

Catalyst's effect on overall reaction

Hi all, In book problem 7.17, the textbook gives us the illustration of a reaction (A->D) and asks whether using a catalyst to accelerate the third step only would change the overall reaction rate. According to the solutions manual, it will not. I understand that the first step is the rate-determini...
by Rebecca Remple 1C
Sat Mar 14, 2020 8:03 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: How to determine the number of intermediates?
Replies: 1
Views: 19

How to determine the number of intermediates?

Hi all, In book problem 7.17, we are asked to determine the number of intermediates by analyzing an illustration of the reaction A -> D. There are three major peaks in the diagram. The solutions manual states that 2 intermediates were formed. How can we tell this from the illustration? Let me know w...
by Rebecca Remple 1C
Sat Mar 14, 2020 7:58 am
Forum: First Order Reactions
Topic: Pseudo First-Order Reaction?
Replies: 2
Views: 55

Pseudo First-Order Reaction?

Hi all, In book problem 7.9, mechanism ii. has the rate law rate = k[C12H22O11][H2O]. It is described as a "pseudo first-order reaction" because the concentration of water is relatively constant, especially in dilute solutions. However, in concentrated solutions this mechanism is said to d...
by Rebecca Remple 1C
Fri Mar 13, 2020 4:01 pm
Forum: Administrative Questions and Class Announcements
Topic: Athena
Replies: 34
Views: 1831

Re: Athena

Dr. Lavelle, Thank you so much for this! I really wish I could have seen you in class one more time before the quarter ends, but I am so grateful for all of the hard work you put into our final in the wake of the conflicts this week. It's been a pleasure learning Chemistry from you :) I always appre...
by Rebecca Remple 1C
Fri Mar 13, 2020 12:42 pm
Forum: Administrative Questions and Class Announcements
Topic: Earthquake FINAL REVIEW SESSION
Replies: 11
Views: 392

Re: Earthquake FINAL REVIEW SESSION

I invited the UAs to attend so it is possible that at least 1 of them will show up and go over the worksheets. I also feel like the UAs will still post the answers but if not and we work through the worksheets we will be sure to share the solutions. That sounds awesome, thank you so much! Good luck...
by Rebecca Remple 1C
Fri Mar 13, 2020 11:12 am
Forum: Administrative Questions and Class Announcements
Topic: UA Final Review - Kate, Riya, Matthew
Replies: 13
Views: 1075

Re: UA Final Review - Kate, Riya, Matthew

Hi everyone! As promised, here is our Final Review worksheet covering Equilibrium through Thermodynamics. We hope that you will find it useful for your studying. Some of these problems are meant to be difficult; do not worry. Approach them as you would any test question: write out what you know, wh...
by Rebecca Remple 1C
Fri Mar 13, 2020 10:24 am
Forum: Administrative Questions and Class Announcements
Topic: Earthquake FINAL REVIEW SESSION
Replies: 11
Views: 392

Re: Earthquake FINAL REVIEW SESSION

Review happening today in delta terrace house 6 lounge 6-9pm!! Hi Mitchell, This is such a great idea! I would love to attend but, unfortunately, I had to leave campus due to the recent concerns and will not be able to :( I was wondering if you or anyone else at the session plans to share solutions...
by Rebecca Remple 1C
Fri Mar 13, 2020 9:21 am
Forum: Administrative Questions and Class Announcements
Topic: Partial Credit
Replies: 8
Views: 105

Re: Partial Credit

My hope is we will do the work ourselves and then submit it as a PDF electronically so it can be graded for partial credit. Yes, I hope so too! Since Dr. Lavelle is giving us so much extra time (1-2 hours) and advising us to use technology at the library, I hope this means we will be allowed to sub...
by Rebecca Remple 1C
Thu Mar 12, 2020 10:39 am
Forum: Administrative Questions and Class Announcements
Topic: Take Home Final
Replies: 16
Views: 219

Take Home Final

Hi all, I hope you are all doing well and staying safe! I am currently adjusting my study strategies for the new final situation. I have never had a "take home" final before, so I was wondering if anyone has experience with these? Will there be a strict time limit, or do these types of fin...
by Rebecca Remple 1C
Thu Mar 12, 2020 10:29 am
Forum: Administrative Questions and Class Announcements
Topic: FinalReview Sessions
Replies: 3
Views: 134

Re: FinalReview Sessions

Does anyone know if Matthew's and Lyndon's final review got posted for us to work on? or was that canceled because of the current situation? Hi Nikki, You can find Matthew, Riya, and Kate's worksheet here: https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=160&t=62044&p=236759&sid=5471...
by Rebecca Remple 1C
Thu Mar 12, 2020 10:25 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Just a reminder about pH and pKa!
Replies: 2
Views: 101

Re: Just a reminder about pH and pKa!

Comparing pKa/pKb with pH/pOH will be important to know how to do on the final - I think! See...pKa = -log(Ka), so the higher the pKa, the lower the Ka. Ka = \frac{[A-][H+]}{[HA]} Lower Ka means higher products - and lower H+ pH = -log(H+), which means the higher the pH, the lower the H+ Therefore,...
by Rebecca Remple 1C
Wed Mar 11, 2020 11:47 am
Forum: Administrative Questions and Class Announcements
Topic: UA Final Review - Kate, Riya, Matthew
Replies: 13
Views: 1075

Re: UA Final Review - Kate, Riya, Matthew

Hi Kate, Riya, and Matthew, Thank you all for your hard work this quarter! Your review sessions have been incredibly helpful. I'll definitely miss seeing you all at the final review session, but I'm so grateful for all of your help. Your review worksheet looks great and I look forward to working thr...
by Rebecca Remple 1C
Wed Mar 11, 2020 11:32 am
Forum: Administrative Questions and Class Announcements
Topic: ENDGAME Review Session
Replies: 71
Views: 2542

Re: ENDGAME Review Session

Hey Lyndon! Thank you so much for all of your hard work this quarter. I've been using your worksheets to study since 14A and they are so helpful. You've put so much work into everything you do and I really appreciate it. I'm sad to see that the session is cancelled but I will definitely be using you...
by Rebecca Remple 1C
Sat Mar 07, 2020 3:54 pm
Forum: Balancing Redox Reactions
Topic: confusing homework question
Replies: 4
Views: 66

Re: confusing homework question

in 6L.5) part b) why do you add Pt as a solid for the Iodine anode reaction? You are already given the solid I2(s) so why to you need an inert conductor? Hi there, While I 2 is a solid, it is not a metal. The electrode needs to be a solid metal to conduct electricity. Therefore solid platinum metal...
by Rebecca Remple 1C
Sat Mar 07, 2020 3:51 pm
Forum: General Rate Laws
Topic: Unique Average Reaction Rate [ENDORSED]
Replies: 4
Views: 59

Re: Unique Average Reaction Rate [ENDORSED]

Rate = -(1/a)(d[A]/dt) where a is the stoichiometric coefficient for A in the reaction, if A is a reactant. For products, the sign is positive. Basically, you are looking at how fast reactants are consumed and products are created relative to each other, using the stoichiometric coefficients For th...
by Rebecca Remple 1C
Sat Mar 07, 2020 3:46 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams: single vertical line between two solids
Replies: 5
Views: 84

Re: Cell Diagrams: single vertical line between two solids

Dr Lavelle answered this question a few years back and said “you separate chemicals in different phases using a single vertical line and if you have multiple chemicals in the same phase (say 2 aqueous solutions) you separate them with a comma. Then, you separate cathode and anode by using a double ...
by Rebecca Remple 1C
Sat Mar 07, 2020 3:45 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Graphical Depiction of Reaction (Book Problem 5G.17)
Replies: 2
Views: 53

Re: Graphical Depiction of Reaction (Book Problem 5G.17)

The two gases never equal each other because the K constant is greater than one. At the start of the reaction, Q is larger than K, so the backward reaction is favored to go to equilibrium. Because of this, the pressure for 2I is much larger, and it will come down to equilibrium levels as I2 increas...
by Rebecca Remple 1C
Mon Mar 02, 2020 9:49 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: E° Being Negative
Replies: 1
Views: 18

Re: E° Being Negative

During week 7, there was in an example regarding calculating the potential difference on Cu/Zn battery (Cu2+(aq) + Zn(s) ---> Cu(s) + Zn2+. It was then stated that the E°Cu was 0.34 V and that E°Zn was -0.76 V. So, I wanted to ask: 1) If given a problem similar to this, would the E° values be given...
by Rebecca Remple 1C
Mon Mar 02, 2020 9:44 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: 6O.1
Replies: 2
Views: 86

Re: 6O.1

A 1.0 m NiSO4(aq) solution was electrolyzed by using inert electrodes. Write (a) the cathode reaction; (b) the anode reaction (c) With no overpotential at the electrodes, what is the minimum potential that must be supplied to the cell for the onset of electrolysis? The solution manual uses the E^o ...
by Rebecca Remple 1C
Mon Mar 02, 2020 9:39 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams: single vertical line between two solids
Replies: 5
Views: 84

Cell Diagrams: single vertical line between two solids

Hi all, In the solutions manual, the cell diagram is sometimes written as solid | solid | aqueous solution || aqueous solution | solid | solid. For example, book problem 6L.7c writes the solution as Cd (s) | Cd(OH)2 | KOH (aq) || Ni(OH)3 (s) | Ni(OH)2 (s) | Ni (s). Why is it written like this instea...
by Rebecca Remple 1C
Sun Mar 01, 2020 2:55 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Graphical Depiction of Reaction (Book Problem 5G.17)
Replies: 2
Views: 53

Graphical Depiction of Reaction (Book Problem 5G.17)

Hi all, I am currently confused on how to solve 5G.17 in the textbook. I understand that, because the Gibbs Free Energy is positive, I2 increases in pressure while I decreases in pressure. However, I found the answer in the Solutions Manual confusing. Why does the pressure of I2 never equal the pres...
by Rebecca Remple 1C
Sat Feb 29, 2020 4:03 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Product in Concentration Cells
Replies: 1
Views: 23

Re: Product in Concentration Cells

Why is the solution with lower concentration the product in a concentration cell? Hi Labiba, The solution with a lower concentration will gain ions as the concentration cell approaches equilibrium. It will increase in concentration. Therefore, the solution with a lower concentration is a product so...
by Rebecca Remple 1C
Sat Feb 29, 2020 3:54 pm
Forum: Balancing Redox Reactions
Topic: Difference between balancing Basic and Acidic
Replies: 3
Views: 32

Re: Difference between balancing Basic and Acidic

Is the only difference between balancing basic and acidic reactions whether you add H+ or OH? Also, do you guys have any tips for balancing? Hi Rita, From what I understand, that is the most important difference between the two! I spoke with Matthew Tran, a UA, regarding balancing tips. I thought h...
by Rebecca Remple 1C
Sat Feb 29, 2020 3:39 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Current flow
Replies: 2
Views: 43

Re: Current flow

I’m having trouble understanding why a current flows from cathode to anode, and electron flows from anode to cathode. What is another way to visualize this? Hi there, After reading up, it seems that the current is always flowing in the opposite direction of electrons. Therefore, if electrons flow f...
by Rebecca Remple 1C
Sat Feb 29, 2020 3:32 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Difference in concentration
Replies: 2
Views: 24

Re: Difference in concentration

I remember hearing in lecture, regarding galvanic cells, that a difference in concentration between two solutions causes an electric flow. I don't really understand what this means. Could someone elaborate? Hi Samuel, I think this may be referring to concentration cells, which are a type of galvani...
by Rebecca Remple 1C
Sat Feb 29, 2020 3:26 pm
Forum: Balancing Redox Reactions
Topic: redox reactions in acidic/basic solution
Replies: 1
Views: 27

Re: redox reactions in acidic/basic solution

How does a rxn occurring in an acidic/basic solution assist/affect the redox reaction? In this case, how are H3O+ and OH- ions involved in oxidizing or reducing an element? Hi John, Certain components of an acidic/basic solution (usually water, H+, and OH-) can be used to balance reduction and oxid...
by Rebecca Remple 1C
Sun Feb 23, 2020 3:27 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: work
Replies: 1
Views: 34

Re: work

What would be some examples of work that the battery system does? Hi Ami, From what I understand, the Galvanic cell (I assume this is what you are referring to) transforms chemical energy to electrical energy that can be used to do work. LibreTexts gives a great example of a cell comprised of zinc ...
by Rebecca Remple 1C
Sun Feb 23, 2020 3:18 pm
Forum: Administrative Questions and Class Announcements
Topic: Dr. Lavelle's Office Hours
Replies: 2
Views: 87

Re: Dr. Lavelle's Office Hours

Chem_Mod wrote:Same answer I gave here: viewtopic.php?f=160&t=59353&p=223555&hilit=office+hours

Thank you so much for your help! It means a lot :)

-Rebecca
by Rebecca Remple 1C
Sun Feb 23, 2020 3:17 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Anode & cathode
Replies: 5
Views: 49

Re: Anode & cathode

Does anyone have any tips to memorize that the anode is where oxidation occurs, and the cathode is where reduction occurs? Hi Alyssa, The way I memorize it is the same way I memorize cations (+) and anions (-). The cathode is associated with a positive sign because it is where reduction occurs; red...
by Rebecca Remple 1C
Sun Feb 23, 2020 3:14 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Notation of Species
Replies: 3
Views: 16

Re: Notation of Species

When would we use a comma versus a single line between the reactants and products? Hi Chloe, The single line denotes that the two species are in different phases (e.g. one is a gas while the other is aqueous). A comma is used if they are in the same phase (e.g. both are gases). I hope this helps! -...
by Rebecca Remple 1C
Sun Feb 23, 2020 3:08 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: work
Replies: 8
Views: 63

Re: work

Will work always negative, because work should not be done on the system (which in this case is the battery system)? Thanks in advance. Hi Ami, A negative sign for work indicates that energy is leaving the system. Negative work means that the system does work on its surroundings. A positive sign fo...
by Rebecca Remple 1C
Wed Feb 19, 2020 1:39 pm
Forum: Administrative Questions and Class Announcements
Topic: Dr. Lavelle's Office Hours
Replies: 2
Views: 87

Dr. Lavelle's Office Hours

Hi all, I was wondering if Dr. Lavelle has Office Hours for this course and, if so, where and when they are? I know he had Office Hours last quarter in 14A, and I would like to meet with him before the end of the quarter to discuss the class. If anyone has information on this matter, please let me k...
by Rebecca Remple 1C
Wed Feb 19, 2020 1:36 pm
Forum: Balancing Redox Reactions
Topic: Test 2 [ENDORSED]
Replies: 12
Views: 120

Re: Test 2 [ENDORSED]

Aiden Metzner 2C wrote:Is test 2 next week? And if so what subject areas is it covering?

Hi Aiden,

Dr. Lavelle moved Test 2 to week nine. It will cover outlines 4 and 5. Hope this helps!

-Rebecca
by Rebecca Remple 1C
Sun Feb 16, 2020 5:47 pm
Forum: Administrative Questions and Class Announcements
Topic: Video Outlines
Replies: 3
Views: 107

Re: Video Outlines

Omar Selim 1D wrote:Are there video outlines for any of the recent topics?

Hi Omar,

I haven't seen any posted. Maybe he will upload some later if there is student demand for them!

Best,
Rebecca
by Rebecca Remple 1C
Sun Feb 16, 2020 5:45 pm
Forum: Administrative Questions and Class Announcements
Topic: Extra Credit
Replies: 7
Views: 154

Re: Extra Credit

I missed 5 points for the chemistry community. Will there be extra points in the class? Hi there, Unfortunately, there is no extra offered in this course. Dr. Lavelle has stated that he will adjust grades after all points are entered (meaning after the final) if necessary, although there is not a &...
by Rebecca Remple 1C
Sun Feb 16, 2020 5:43 pm
Forum: Administrative Questions and Class Announcements
Topic: when are your #of posts on CC collected each week?
Replies: 4
Views: 105

Re: when are your #of posts on CC collected each week?

Sue Bin Park 2I wrote:do the TAs collect them on mondays? fridays?

Hi Sue,

I agree with the users above me. The cutoff is Sunday night at 11:59 PM unless Dr. Lavelle states otherwise. I hope this helps!

Best,
Rebecca
by Rebecca Remple 1C
Wed Feb 12, 2020 5:12 pm
Forum: Calculating Work of Expansion
Topic: Pizza Rolls #6
Replies: 1
Views: 45

Re: Pizza Rolls #6

"You have a system consisting of 0.40 moles of an ideal gas contained in a 100.0L container at 1.0 atm. You just love chemistry to a fault, so you perform a series of steps to the system. First, you perform an isobaric compression of the container to 10.0L. Then, you pressurize the system to 1...
by Rebecca Remple 1C
Wed Feb 12, 2020 2:06 pm
Forum: Phase Changes & Related Calculations
Topic: Rotational/Translational Contributions?
Replies: 2
Views: 56

Re: Rotational/Translational Contributions?

The values given indicate what the heat capacity of an ideal gas could be at constant volume and constant pressure. the main concept to know here is that the change in internal energy = (3/2)Rdelta T. You can find the heat capacity by dividing delta U by delta T. You can use the "How Do We Kno...
by Rebecca Remple 1C
Mon Feb 10, 2020 5:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Sign of Energy Density
Replies: 2
Views: 33

Re: Sign of Energy Density

I think energy density is always positive, since the definition of energy density is "the amount of energy stored in a given system or region of space per unit volume." I don't think energy can be negative (but I may be wrong), so energy density can't be negative. Hi Alice, Thank you so m...
by Rebecca Remple 1C
Mon Feb 10, 2020 4:59 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Double Greater than Sign
Replies: 2
Views: 20

Double Greater than Sign

Hi all, In an example we did in class, Dr. Lavelle wrote "S G >> S L > S s ". I was wondering what the double greater than sign, >>, means in this context. Why is the difference between gas and liquid different from the difference between liquid and solid? Please let me know. Thank you! -R...
by Rebecca Remple 1C
Sun Feb 09, 2020 6:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Sign of Energy Density
Replies: 2
Views: 33

Sign of Energy Density

Hi all, In homework problem 4D.9 we are asked to calculate the energy density of a reaction. I found the enthalpy, which was negative. This meant that energy/heat was being released. However, according to the solutions manual, the sign changed to positive when calculating the energy density of the r...
by Rebecca Remple 1C
Sun Feb 09, 2020 5:56 pm
Forum: Phase Changes & Related Calculations
Topic: Rotational/Translational Contributions?
Replies: 2
Views: 56

Rotational/Translational Contributions?

Hi all, I am struggling to understand what is meant by rotational and translational contributions. Homework problem 4C.5 deals with these contributions of molecular motions. I understand how to add the two contributions together but do not understand the question conceptually. What do these contribu...
by Rebecca Remple 1C
Sun Feb 09, 2020 5:47 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.23
Replies: 2
Views: 37

Re: 4D.23

Calculate the standard enthalpy of formation of dinitrogen pentoxide from the following data: 2 NO(g) + O2(g) --> 2 NO2(g); delta H° = -114.1 kJ 4 NO2(g) + O2(g) --> 2 N2O5(g); delta H° = -110.2 kJ and from the standard enthalpy of formation of nitric oxide, NO (see Appendix 2A). how do i calculate...
by Rebecca Remple 1C
Sun Feb 09, 2020 5:40 pm
Forum: Phase Changes & Related Calculations
Topic: 4.23
Replies: 1
Views: 30

Re: 4.23

in this problem, we have to use the equation E = hc/λ and calculate the number of photons needed for the rxn will we have to know this and other quantum equations for the midterm? Hi there, From what I understand, we only have to know equations from Dr. Lavelle's Constants and Equations sheet: http...
by Rebecca Remple 1C
Sun Feb 09, 2020 5:36 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Learning outcome fossil fuels
Replies: 2
Views: 48

Re: Learning outcome fossil fuels

On the learning outcomes sheet for "Thermochemistry and the First Law of Thermodynamics" from Dr. Lavelle's class website, it says we should "understand the environmental impact of burning fossil fuels, and the use of alternative fuels as energy sources." Can someone explain how...
by Rebecca Remple 1C
Sat Feb 01, 2020 3:59 pm
Forum: Administrative Questions and Class Announcements
Topic: 14A final solutions
Replies: 6
Views: 76

Re: 14A final solutions

Hi there, I've not seen the solutions posted anywhere, but you can pick up your midterm at 3034 Young Hall! They have them fully graded, so you can see what you missed. You can read more about the process here: https://lavelle.chem.ucla.edu/forum/viewtopic.php?p=214489&sid=8da1e337f667784da8b244...
by Rebecca Remple 1C
Sat Feb 01, 2020 3:58 pm
Forum: Administrative Questions and Class Announcements
Topic: 14A Final Answer Key
Replies: 5
Views: 83

Re: 14A Final Answer Key

Hi Annie, I do not know if the answer key is available, but you can actually pick up your midterm at 3034 Young Hall! They have them fully graded and with many of the correct answers filled in. You can read the thread about it here: https://lavelle.chem.ucla.edu/forum/viewtopic.php?p=214489&sid=...
by Rebecca Remple 1C
Sat Feb 01, 2020 3:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Water and Equilibrium
Replies: 2
Views: 26

Water and Equilibrium

Hi all, I had a question regarding one of the problems in Test #1. In this problem, gaseous H2O effected the equilibrium constant of the system. I was confused by this, because I regarded all forms of water as a pure substance that would not be factored into equilibrium calculations. Does the state ...
by Rebecca Remple 1C
Sat Feb 01, 2020 3:50 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Material
Replies: 13
Views: 122

Re: Midterm Material

Hi there, You can find all of the information regarding the midterm here: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14B/Midterm_Review_Sessions_14B.pdf If you have any trouble with the link, it's located under "Midterm Exam: Review Sessions and Exam Venues" on the 14B c...
by Rebecca Remple 1C
Sat Feb 01, 2020 3:48 pm
Forum: Administrative Questions and Class Announcements
Topic: Fall Quarter Final?
Replies: 12
Views: 246

Re: Fall Quarter Final?

Hi all, Thanks for your replies! I wanted to update everyone about the situation. They are still passing back fall quarter finals from 14A in Young 3034! If you walk into Young Hall, there is a large glass window through which you can speak with staff in the room. You need to give them your Bruincar...
by Rebecca Remple 1C
Sun Jan 26, 2020 3:45 pm
Forum: Administrative Questions and Class Announcements
Topic: Fall Quarter Final?
Replies: 12
Views: 246

Fall Quarter Final?

Hi all, I heard earlier that the Fall quarter final would be available in Young 3034 during week 3. However, I assumed that Dr. Lavelle would send out an email with the times we could come to pick up the exam. I never received instructions about when and how to pick it up. Does anyone know if the ex...
by Rebecca Remple 1C
Mon Jan 20, 2020 7:17 pm
Forum: Student Social/Study Group
Topic: Test 1
Replies: 9
Views: 99

Re: Test 1

are there any past exams to help us study for test 1? does the professor usually post a practice test beforehand? Hi Dina, There is no practice test, but he will pull questions from the assigned homework! I would recommend going through those problems to get a better understanding of the test's con...
by Rebecca Remple 1C
Mon Jan 20, 2020 7:15 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: When to ignore the second (de)protonization?
Replies: 5
Views: 38

Re: When to ignore the second (de)protonization?

I think that you would ignore it if the second deprotonization or third (etc.) does not affect the pH of the solution. In the textbook, it says that for most polyphonic acid, the 2nd or more Ka is so small that pH of the solution isn't really affected. However, for H2SO4, this is an exception where...
by Rebecca Remple 1C
Mon Jan 20, 2020 7:13 pm
Forum: Student Social/Study Group
Topic: Any Worksheets from UA/TA/etc?
Replies: 14
Views: 232

Re: Any Worksheets from UA/TA/etc?

Does anyone know if there are any practice worksheets from UAs, TAs, etc for Chem 14B? I remember for Chem 14A last quarter, some UAs had worksheets posted on here so I'm just wondering if there is any for this course. Hi Jasmine, I hear that some UAs and TAs do worksheets, while others do not. My ...
by Rebecca Remple 1C
Mon Jan 20, 2020 7:05 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: When to ignore the second (de)protonization?
Replies: 5
Views: 38

When to ignore the second (de)protonization?

Hi all, Both homework problems from section 6E ask about the second deprotonization. However, while the second (de)protonization is used to calculate pH in problem 6E.1, it is ignored in the problems in 6E.3. I was wondering if someone can explain why this is. At what point does the second (de)proto...
by Rebecca Remple 1C
Sat Jan 18, 2020 4:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pKa versus pH
Replies: 3
Views: 40

Re: pKa versus pH

I understand the difference between pKa and pH in terms of the formula, but I don't really understand how they differ conceptually. Adding to this, I don't understand why when pKa > pH, it's acidic and when pKa < pH, it's basic. Does it have something to do with the conjugate base? It has to be rig...
by Rebecca Remple 1C
Sat Jan 18, 2020 4:11 pm
Forum: Administrative Questions and Class Announcements
Topic: UA Sessions
Replies: 2
Views: 34

Re: UA Sessions

Will there be UA sessions this Monday? Hi Ayushi, I had the same question! Unfortunately, I was told that there most likely will not because Office Hours and classes are not occurring on that day. If I hear anything else to the contrary, I will be sure to let you know! Good luck on the test :) -Reb...
by Rebecca Remple 1C
Sat Jan 18, 2020 4:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Getting Back 14A Final Exam
Replies: 3
Views: 51

Re: Getting Back 14A Final Exam

Someone said they went to the room to check and they said by Week 3. I don't think it'd be possible to get your test prior to your test a day or so in advance. If anything, I'd suggest going to pick it up an hour or so before your test if they're open. Good luck! Hi Megan, Thank you for letting me ...
by Rebecca Remple 1C
Sat Jan 18, 2020 2:57 pm
Forum: Ideal Gases
Topic: Solids and Liquids [ENDORSED]
Replies: 10
Views: 95

Re: Solids and Liquids [ENDORSED]

I agree with Fiona and McKenna! However, I am still confused on the matter of liquids being pure substancews. Can someone clarify how a liquid is different from an aqueous solution and give examples of each? From what I understand, aqueous solutions have a solute and solvent, and liquids do not. Ca...
by Rebecca Remple 1C
Sat Jan 18, 2020 2:55 pm
Forum: Administrative Questions and Class Announcements
Topic: Learning Sessions on Monday?
Replies: 2
Views: 35

Learning Sessions on Monday?

Hi all, I was wondering if there will be any UA-led study sessions during the Monday holiday? I was assuming not because it is a day off for all students, but I wasn't sure if some UAs might be hosting them anyways. I'm especially interested in Step-Up or Workshop sessions. Please let me know your t...
by Rebecca Remple 1C
Sat Jan 18, 2020 2:52 pm
Forum: Administrative Questions and Class Announcements
Topic: Getting Back 14A Final Exam
Replies: 3
Views: 51

Getting Back 14A Final Exam

Hi all, I hope you're doing well! I was wondering when we will be able to get back the Chemistry 14A final exam from Dr. Lavelle's classes last quarter. I was informed that they will be given back during Week 3 of this quarter. I was hoping to review my old final before Test 1 so I can better unders...
by Rebecca Remple 1C
Sat Jan 11, 2020 3:19 pm
Forum: Ideal Gases
Topic: Law of Effusion, Kinetic Model, and Maxwell Distribution
Replies: 3
Views: 40

Re: Law of Effusion, Kinetic Model, and Maxwell Distribution

Focus 3D covers Graham's Law of Effusion, the Kinetic Model of Gases, and the Maxwell Distribution of Speeds. Do you think we will need to know these concepts in depth, and can anyone give a short summary of these, if possible? Thanks! Hi Ariel, The syllabus doesn't list these concepts, so I doubt ...
by Rebecca Remple 1C
Sat Jan 11, 2020 3:15 pm
Forum: Administrative Questions and Class Announcements
Topic: Required number of responses for chem community
Replies: 7
Views: 53

Re: Required number of responses for chem community

Tyler Angtuaco 1G wrote:Is the required number of responses for Chemistry Community still 5 responses for Chem14B?

Hi Tyler,

The requirement is still 5 posts per week, as well as the 5 homework problems that are due every discussion. There are 50 points total for the whole quarter. I hope this helps!

-Rebecca
by Rebecca Remple 1C
Sat Jan 11, 2020 3:12 pm
Forum: Ideal Gases
Topic: Solids and Liquids [ENDORSED]
Replies: 10
Views: 95

Re: Solids and Liquids [ENDORSED]

I agree with Fiona and McKenna! However, I am still confused on the matter of liquids being pure substancews. Can someone clarify how a liquid is different from an aqueous solution and give examples of each? From what I understand, aqueous solutions have a solute and solvent, and liquids do not. Can...
by Rebecca Remple 1C
Sat Jan 11, 2020 3:06 pm
Forum: Ideal Gases
Topic: K vs Q [ENDORSED]
Replies: 7
Views: 74

Re: K vs Q [ENDORSED]

I have a question about when to use K and Q. Also, what's the main difference between the two. Thank you. :) Hi Donavin, From what I understand, K is the equilibrium constant while Q is the reaction quotient. K is calculated using the concentrations of reactants and products at equilibrium. Q is no...
by Rebecca Remple 1C
Sat Jan 11, 2020 3:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial Pressure
Replies: 7
Views: 44

Re: Partial Pressure

Donavin Collins 1F wrote:I need a bit of clarification for partial pressure. Is it only used for gases?

Hi Donavin,

From what I understand partial pressures are only used for gases :) This is true for all of the practice problems that include gases as reactants or products. I hope this helps!

-Rebecca
by Rebecca Remple 1C
Sun Dec 08, 2019 9:12 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Strong vs. Weak Acids
Replies: 3
Views: 123

Re: Strong vs. Weak Acids

Hi, HOI and HOCl are oxoacids. Look at stability of conjugate base ClO-. The conjugate base is more stable when the electron density is distributed over more atoms versus concentrated on the oxygen only. Cl is more electronegative than I, so it can withdraw more electron density from the Oxygen. Th...
by Rebecca Remple 1C
Sun Dec 08, 2019 9:10 am
Forum: Identifying Acidic & Basic Salts
Topic: Mini Marshmallows 1C - Acidic Salt?
Replies: 2
Views: 88

Re: Mini Marshmallows 1C - Acidic Salt?

NO3- participates in the reaction, but it does not change the acidity of the solution, and therefore does not affect the pH, so we can disregard it when considering pH levels. This is because NO3- is the conjugate base of HNO3, which is a strong acid and the conjugate bases of strong acids do not a...
by Rebecca Remple 1C
Sat Dec 07, 2019 8:13 pm
Forum: Identifying Acidic & Basic Salts
Topic: Mini Marshmallows 1C - Acidic Salt?
Replies: 2
Views: 88

Mini Marshmallows 1C - Acidic Salt?

Hey again,

In Mini Marshmallows 1C, why does the NO3- in NH4NO3 not participate in the reaction with water, but NH4+ does? I just want to make sure I understand this conceptually before the final. Thank you!

-Rebecca
by Rebecca Remple 1C
Sat Dec 07, 2019 8:11 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4684

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

Hey again,

In Mini Marshmallows 1C, why does the NO3- in NH4NO3 not participate in the reaction with water, but NH4+ does? I just want to make sure I understand this conceptually before the final. Thank you!

-Rebecca
by Rebecca Remple 1C
Sat Dec 07, 2019 7:15 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4684

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

Can someone explain how to get the pH for 34. I got the moles of each compound but can’t seem to get the overall pH. Hi Jonathan, Using the moles for CaO and HCl, you can determine how many moles of OH- and H+ are produced. You need to write out the equations in water to do so. Note that 2 moles of...
by Rebecca Remple 1C
Sat Dec 07, 2019 7:10 pm
Forum: Air Pollution & Acid Rain
Topic: What do we need to know?
Replies: 4
Views: 120

Re: What do we need to know?

does anyone know if its going to be more focused on material after the mid-term or is it just going to be random? Hi there, I heard that the questions will be pretty evenly distributed, so a good portion of the final will cover topics from the midterm as well as from after it. I hope this helps! Go...
by Rebecca Remple 1C
Sat Dec 07, 2019 7:09 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Strong vs. Weak Acids
Replies: 3
Views: 123

Strong vs. Weak Acids

Hi all, I'm preparing for the final by reviewing the rules for strong and weak acids. I understand that bond length in HF and HI makes HI a stronger acid, because it is more likely to lose a proton. However, why is HOCl stronger than HOI? I read through the explanation in the review worksheet, but I...
by Rebecca Remple 1C
Sat Dec 07, 2019 7:03 pm
Forum: Hybridization
Topic: Marshmallows #17 - hybridization in pi bonds
Replies: 2
Views: 79

Re: Marshmallows #17 - hybridization in pi bonds

My guess is that it's a typo. Pi bonds result from the overlapping of p orbitals specifically (think of it like two infinity symbols, one on top of the other) so the pi bond should only have p character. Hi Aadil, Thank you so much for replying! I'm glad to know I'm not the only one who thought tha...
by Rebecca Remple 1C
Sat Dec 07, 2019 6:19 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4684

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

Hi all, I was going through the final review packet and have been having trouble understanding part of problem 17. In the problem, it asks us to draw C5H5NO2 and label all of the sigma and pi bonds. I understand most of the question, but one of the pi bonds is troubling me. Near the top of the molec...
by Rebecca Remple 1C
Sat Dec 07, 2019 6:17 pm
Forum: Hybridization
Topic: Marshmallows #17 - hybridization in pi bonds
Replies: 2
Views: 79

Marshmallows #17 - hybridization in pi bonds

Hi all, I was going through Lyndon's final review packet and have been having trouble understanding part of problem 17. In the problem, it asks us to draw C5H5NO2 and label all of the sigma and pi bonds. I understand most of the question, but one of the pi bonds is troubling me. Near the top of the ...
by Rebecca Remple 1C
Sat Dec 07, 2019 9:58 am
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4684

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

Hi there! Thank you so much for sharing these practice problems. I was wondering if the answer key to the regular worksheet will be posted soon? I was not able to make the session but have been working on the problems, so I would love to be able to refer to it. Thank you!
by Rebecca Remple 1C
Thu Nov 28, 2019 4:28 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Final Exam
Replies: 10
Views: 150

Re: Final Exam

I wasn't sure which section to put this under, but will the final exam include all the content we have covered including the fundamentals? Thank you. Hi there, The final will be cumulative, although recent material will probably make up the majority of it. You can expect to see questions that combi...
by Rebecca Remple 1C
Thu Nov 28, 2019 4:26 pm
Forum: Naming
Topic: Oxidation
Replies: 14
Views: 182

Re: Oxidation

Also can anyone explain what oxidation is? And what Dr. Lavelle meant by oxidation states? I don't remember him explaining the concept in class. Hi Kennedi, I agree with the other commenters about oxidation states and numbers. To answer your first questions, an oxidation reaction represents the los...
by Rebecca Remple 1C
Thu Nov 28, 2019 4:22 pm
Forum: Bronsted Acids & Bases
Topic: Writing Equations
Replies: 1
Views: 28

Re: Writing Equations

How do you know when to write an equation with the arrow pointing one way versus the set of arrows pointing both ways? Hi there, I talked to my TA about this and, apparently, many chemical equations can be written either way. Most acid-base reactions are "irreversible" because the backwar...
by Rebecca Remple 1C
Thu Nov 28, 2019 4:18 pm
Forum: Hybridization
Topic: single vs double vs triple bonds
Replies: 4
Views: 45

Re: single vs double vs triple bonds

Why doesn't the number of bonds affect which hybrid orbital is formed? For instance, in ethylene c2h4, why is the double bond in between the carbons just two sp^2 hybrid orbitals instead of two individual sp^3 orbitals (since there are four bonds formed by carbon in total)? Hi Chris, I agree with t...
by Rebecca Remple 1C
Thu Nov 28, 2019 4:15 pm
Forum: Bronsted Acids & Bases
Topic: Writing Equations
Replies: 1
Views: 24

Re: Writing Equations

When you're writing out the equations for acid-base reactions, how do you know whether the molecules (for both products and reactants) will be an aqueous solution or a liquid if the question doesn't specify? Hi Labiba, This is confusing to me too! However I have found that, in general, products nor...
by Rebecca Remple 1C
Thu Nov 21, 2019 7:05 pm
Forum: Sigma & Pi Bonds
Topic: sigma and pi bonds
Replies: 3
Views: 41

Re: sigma and pi bonds

If you see a single bond, it will be a sigma bond. Pi bonds occur whenever there's a p-orbital interacting with another p-orbital, so when there's a double bond, one will be a pi bond and the other will be a sigma bond (because if you have 2 pi bonds the bond will break). so every bond ever? in pol...
by Rebecca Remple 1C
Thu Nov 21, 2019 7:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles for trigonal bipyramidal and octahedral
Replies: 2
Views: 37

Re: Bond angles for trigonal bipyramidal and octahedral

What are the bond angles for Trigonal Bipyramidal and octahedral arrangements when they have one and two lone pairs? i.e. bond angles for seesaw, t shaped, square pyramidal and square planar? Hi there, I agree with the previous answer! If you have any trouble visualizing this, I have attached a stu...
by Rebecca Remple 1C
Thu Nov 21, 2019 6:56 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: in need of test 2 practice problems
Replies: 5
Views: 89

Re: in need of test 2 practice problems

hello! does anyone have practice problems for test 2? from any UA sessions or anything? please copy here (or email/text me) Hi there, I would recommend revisiting the homework problems in section 2E of the textbook. Also, if you have difficulty visualizing 3D molecular structures, I would recommend...
by Rebecca Remple 1C
Thu Nov 21, 2019 6:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 2
Replies: 14
Views: 159

Re: Test 2

Does anyone have any advice for remembering molecular shape? Hi Cassandra, I think it's good to start by remembering molecular geometry, where lone pairs are counted as regions of electron density. If there are 2 areas of electron density, the shape is linear and the angle 180 degrees. If there are...
by Rebecca Remple 1C
Wed Nov 20, 2019 3:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape vs. Geometry
Replies: 5
Views: 71

Molecular Shape vs. Geometry

Hey all, I hope you're doing well! Can someone please explain the difference between molecular shape and geometry? I am having a difficult time understanding which is which, as the different resources I am using have varied definitions. If possible, can you provide examples for both? Thank you in ad...
by Rebecca Remple 1C
Wed Nov 13, 2019 3:22 pm
Forum: *Particle in a Box
Topic: Principle quantum number
Replies: 2
Views: 107

Re: Principle quantum number

Hi Clara, If you are given enough information, you can do this using the Rydberg formula. You can find this formula on the constants and equations sheets. This will work if you known one of the principle quantum numbers (e.g. at ground state, Hydrogen's principle quantum number = 1). You can then pl...
by Rebecca Remple 1C
Wed Nov 13, 2019 3:19 pm
Forum: DeBroglie Equation
Topic: Use
Replies: 2
Views: 96

Re: Use

Hi Clara! You can use it if you need to find wavelength and are given values for mass and/or speed of an object. It can be used for large objects, like baseballs, which cannot be plugged into the light-specific equations like c=wavelength*frequency. If you aren't given a mass, you can find masses fo...
by Rebecca Remple 1C
Wed Nov 13, 2019 3:15 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Answers
Replies: 10
Views: 146

Re: Midterm Answers

Here's the link: https://lavelle.chem.ucla.edu/wp-conten ... rm_ans.pdf
If the link doesn't work, you can find it on his Chemistry 14A class website under "Exam Information" :) I hope this helps!
by Rebecca Remple 1C
Wed Nov 13, 2019 3:14 pm
Forum: Administrative Questions and Class Announcements
Topic: Regrade requests
Replies: 3
Views: 103

Re: Regrade requests

You can email your TA, or speak to them during Office Hours or Discussion. I hope this helps!
by Rebecca Remple 1C
Wed Nov 13, 2019 3:13 pm
Forum: Administrative Questions and Class Announcements
Topic: Class grading
Replies: 12
Views: 250

Re: Class grading

Hi Tyler! I agree with all the previous replies. Additionally, there's a chance (but no guarantee) that Dr. Lavelle may curve grades if the class average is low. From what I hear, he would only curve up, meaning that it would raise your final grade. However, if the class average is above or at his e...
by Rebecca Remple 1C
Wed Nov 13, 2019 3:10 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm grade
Replies: 4
Views: 74

Re: Midterm grade

Hi Savannah! We got our physical midterms back in my class. If you weren't able to get yours, you can email your TA or go to their Office Hours. I heard that scores were supposed to be posted to CCLE today, but they were delayed. If you can't get the midterm back physically, I'm sure they will be up...
by Rebecca Remple 1C
Wed Nov 13, 2019 3:08 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ground state?
Replies: 6
Views: 171

Ground state?

Hi all, I hope you're all doing well! I'm a bit confused about the meaning of the term "ground state". In the test, one question asked about a "ground state ion". I originally thought that being in a ground state means that an atom has no charge. However, since ions are charged, ...
by Rebecca Remple 1C
Fri Nov 08, 2019 2:37 pm
Forum: Administrative Questions and Class Announcements
Topic: Discussion-Week 9
Replies: 3
Views: 51

Re: Discussion-Week 9

Hello! I was wondering if anyone knows whether or not we will have discussion sections week 9. This is the week of Thanksgiving so I am trying to plan when to go home. They won't have discussion during the day offs for Thanksgiving break (Thursday and Friday). However, if you have discussion Monday...
by Rebecca Remple 1C
Fri Nov 08, 2019 2:35 pm
Forum: Lewis Structures
Topic: Midterm grades
Replies: 26
Views: 386

Re: Midterm grades

Does anyone know when midterm grades will be released? I'm assuming that we'll get them back week 7. Dr. Lavelle shared in class that the average score was 75%, which implies that they've been mostly graded. However, I'm sure they still have work to do in terms of finalizing the grades, assigning p...
by Rebecca Remple 1C
Fri Nov 08, 2019 2:32 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: Monday Lecture
Replies: 2
Views: 46

Re: Monday Lecture

Since we don't have school on Monday, is there anything we need to prepare for the Friday lecture or no? There's no lecture on Monday, and Dr. Lavelle didn't mention any extra work you need to do in its place. I'm assuming there won't be any extra preparation/assignments required. Just the usual Ch...
by Rebecca Remple 1C
Fri Nov 08, 2019 2:30 pm
Forum: Trends in The Periodic Table
Topic: Atomic Radii
Replies: 10
Views: 104

Re: Atomic Radii

Why does atomic radii decrease even though the number of protons increase as you go across a period? I agree with the previous responses! I wanted to add that, in general, electrons repel each other and are attracted to protons. Having more protons in the nucleus, and thus a higher/more positive ch...

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