Your tribute and thank-you slides are excellent!
Tonight I will enjoy reading more of them.
Search found 19733 matches
- Tue Mar 16, 2021 7:02 pm
- Forum: Administrative Questions and Class Announcements
- Topic: THANK YOU DR LAVELLE!
- Replies: 47
- Views: 928
- Tue Mar 16, 2021 12:46 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 416
- Views: 144029
Re: Saying Thank You to Dr. Lavelle
Thank you all!
We had a great two quarters!
Wishing you all the best.
We had a great two quarters!
Wishing you all the best.
- Tue Mar 16, 2021 10:25 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Frequency factor and Activation energy [ENDORSED]
- Replies: 1
- Views: 28
Re: Frequency factor and Activation energy [ENDORSED]
The preexponential/frequency parameter, A, is considered a separate parameter from activation energy, Ea, in the Arrhenius equation.
- Tue Mar 16, 2021 10:22 am
- Forum: Administrative Questions and Class Announcements
- Topic: Acids and Bases Review- Ty
- Replies: 1
- Views: 114
Re: Acids and Bases Review- Ty
These were helpful. Thank you.
- Tue Mar 16, 2021 10:21 am
- Forum: Administrative Questions and Class Announcements
- Topic: Practice problems for thermodynamics (conceptual)
- Replies: 1
- Views: 139
Re: Practice problems for thermodynamics (conceptual)
These were helpful. Thank you.
- Tue Mar 16, 2021 10:20 am
- Forum: Administrative Questions and Class Announcements
- Topic: Matthew's Workshop - Week 9
- Replies: 1
- Views: 370
Re: Matthew's Workshop - Week 9
These were helpful. Thank you.
- Tue Mar 16, 2021 10:20 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Kate's Week 8 Workshop Winter 2021
- Replies: 1
- Views: 125
Re: Kate's Week 8 Workshop Winter 2021
These were helpful. Thank you.
- Tue Mar 16, 2021 10:20 am
- Forum: Administrative Questions and Class Announcements
- Topic: Matthew's Workshop - Week 8
- Replies: 1
- Views: 258
Re: Matthew's Workshop - Week 8
These were helpful. Thank you.
- Tue Mar 16, 2021 10:20 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Kate's Midterm Review
- Replies: 1
- Views: 174
Re: Kate's Midterm Review
These were helpful. Thank you.
- Tue Mar 16, 2021 10:19 am
- Forum: Administrative Questions and Class Announcements
- Topic: Matthew's Workshop - Week 7
- Replies: 1
- Views: 431
Re: Matthew's Workshop - Week 7
These were helpful. Thank you.
- Tue Mar 16, 2021 10:17 am
- Forum: Administrative Questions and Class Announcements
- Topic: Matthew's Workshop - Week 6
- Replies: 1
- Views: 392
Re: Matthew's Workshop - Week 6
These were helpful. Thank you.
- Tue Mar 16, 2021 10:17 am
- Forum: Administrative Questions and Class Announcements
- Topic: Matthew's Workshop - Week 5
- Replies: 1
- Views: 344
Re: Matthew's Workshop - Week 5
These were helpful. Thank you.
- Tue Mar 16, 2021 10:17 am
- Forum: Administrative Questions and Class Announcements
- Topic: Matthew's Workshop - Week 3
- Replies: 1
- Views: 437
Re: Matthew's Workshop - Week 3
These were helpful. Thank you.
- Tue Mar 16, 2021 10:17 am
- Forum: Administrative Questions and Class Announcements
- Topic: Julia's Step-Up Session Week 3
- Replies: 1
- Views: 92
Re: Julia's Step-Up Session Week 3
These were helpful. Thank you.
- Tue Mar 16, 2021 10:16 am
- Forum: Administrative Questions and Class Announcements
- Topic: Matthew's Workshop - Week 2
- Replies: 1
- Views: 435
Re: Matthew's Workshop - Week 2
These were helpful. Thank you.
- Tue Mar 16, 2021 8:45 am
- Forum: General Rate Laws
- Topic: Manipulating rate law equations [ENDORSED]
- Replies: 1
- Views: 17
Re: Manipulating rate law equations [ENDORSED]
Working through examples is the best way to practice. Take a look at the example I did in class and the examples in the textbook, assigned problems in the textbook, and Sapling Learning.
- Tue Mar 16, 2021 8:42 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts and Intermediates
- Replies: 1
- Views: 13
Re: Catalysts and Intermediates
Michael Iter 2F wrote:For example, could there maybe be a molecule that appears as an intermediate and then catalyzes the subsequent steps of the reaction?
Yes that is possible.
- Tue Mar 16, 2021 8:40 am
- Forum: Zero Order Reactions
- Topic: Sapling #4 (week 9/10) [ENDORSED]
- Replies: 4
- Views: 35
Re: Sapling #4 (week 9/10) [ENDORSED]
Good answer.
- Tue Mar 16, 2021 1:16 am
- Forum: Administrative Questions and Class Announcements
- Topic: THANK YOU DR LAVELLE!
- Replies: 47
- Views: 928
Re: THANK YOU DR LAVELLE!
I am thankful for so many terrific students.
I am reading and enjoying each slide one at a time. They are so well done. Creative!
Spacing out my reading of them, some each night, to enjoy them.
Great to see many TA and UA acknowledgments.
:-)
I am reading and enjoying each slide one at a time. They are so well done. Creative!
Spacing out my reading of them, some each night, to enjoy them.
Great to see many TA and UA acknowledgments.
:-)
- Tue Mar 16, 2021 1:07 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activation Energy [ENDORSED]
- Replies: 2
- Views: 29
Re: Activation Energy [ENDORSED]
Great answer Amanda.
Dr. DJ LL :-)
Dr. DJ LL :-)
- Tue Mar 16, 2021 1:04 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Rate determining step [ENDORSED]
- Replies: 3
- Views: 27
Re: Rate determining step [ENDORSED]
Good answer.
- Tue Mar 16, 2021 12:34 am
- Forum: Administrative Questions and Class Announcements
- Topic: Chem Community Cut Off [ENDORSED]
- Replies: 1
- Views: 106
Re: Chem Community Cut Off [ENDORSED]
As announced, I extended the Chemistry Community and Sapling deadline to Tuesday morning 9am.
Good answers to Chemistry Community questions will count for missing Chemistry Community points for the quarter.
Good answers to Chemistry Community questions will count for missing Chemistry Community points for the quarter.
- Mon Mar 15, 2021 11:27 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Textbook 6N.13
- Replies: 1
- Views: 31
Re: Textbook 6N.13
Good you resolved it. :-)
- Sun Mar 14, 2021 8:35 pm
- Forum: Administrative Questions and Class Announcements
- Topic: THANK YOU DR LAVELLE!
- Replies: 47
- Views: 928
Re: THANK YOU DR LAVELLE!
I AM SPEACHLESS.
WoW.
I have no idea how to respond to this website :-) https://docs.google.com/presentation/d/ ... c2814b_1_0
THANK YOU!!!
WoW.
I have no idea how to respond to this website :-) https://docs.google.com/presentation/d/ ... c2814b_1_0
THANK YOU!!!
- Sun Mar 14, 2021 8:16 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 416
- Views: 144029
Re: Saying Thank You to Dr. Lavelle
Dear Dr. Lavelle, all the TA's, UA's, and staff who helped make online school possible, Thank you for all of your hard work! With everything going on during this pandemic, I was anxious about being unable to learn or do well in the course. However, you all went above and beyond during these last tw...
- Sun Mar 14, 2021 8:15 pm
- Forum: General Science Questions
- Topic: 14B vs. 14C material
- Replies: 6
- Views: 75
Re: 14B vs. 14C material
14A material will definitely be on the MCAT and probably other standardized STEM exams. LS 7A touches slightly on 14A material with intermolecular forces and stuff. Chem 14D requires basic knowledge of 14A (mostly acid/base knowledge). Chem 153A (biochem) goes over some intermolecular forces from 14...
- Sun Mar 14, 2021 8:07 pm
- Forum: General Science Questions
- Topic: 14B vs. 14C material
- Replies: 6
- Views: 75
Re: 14B vs. 14C material
14C does not cover 14B material; 14C builds mainly on 14A. 14B material shows up again in Physics 5B, Chem 14BL, and the MCAT too, so it's not a bad idea to keep your notes!
- Sun Mar 14, 2021 6:43 pm
- Forum: Administrative Questions and Class Announcements
- Topic: THANK YOU DR LAVELLE!
- Replies: 47
- Views: 928
Re: THANK YOU DR LAVELLE!
Remote learning survey said to contact department for teaching award nominations.
Email to send for Chem nominations: chair@chem.ucla.edu
Email to send for Chem nominations: chair@chem.ucla.edu
- Sun Mar 14, 2021 6:27 pm
- Forum: Student Social/Study Group
- Topic: Mood after finishing gen chem
- Replies: 1
- Views: 40
Re: Mood after finishing gen chem
:-)
Looks like Good Chemistry to me!
Looks like Good Chemistry to me!
- Sun Mar 14, 2021 6:10 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 416
- Views: 144029
Re: Saying Thank You to Dr. Lavelle
Janna Shakiba wrote:Dr. Lavelle, thank you for making me enjoy chemistry for the first time in my LIFE!
lol
It is, what I call, Good Chemistry!
:-)
- Sun Mar 14, 2021 4:53 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 416
- Views: 144029
Re: Saying Thank You to Dr. Lavelle
I'm taking a break from writing my soc paper to tell you, Dr. Lavelle, that I could not be more appreciative of you. Chem 14A and 14B would not have been the same without your amazing energy and commitment to teaching. Your music was awesome, the UA sessions were a life saver, and the only thing th...
- Sun Mar 14, 2021 2:21 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 416
- Views: 144029
Re: Saying Thank You to Dr. Lavelle
Thank you for all the wonderful posts and positive feedback. It encourages me to continue my focused and significant efforts to assist students.
- Sun Mar 14, 2021 2:13 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L.5 Part D [ENDORSED]
- Replies: 3
- Views: 69
Re: 6L.5 Part D [ENDORSED]
Welcome
- Sun Mar 14, 2021 9:09 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: textbook 6.73 [ENDORSED]
- Replies: 1
- Views: 51
Re: textbook 6.73 [ENDORSED]
The textbook discusses the aluminum-air fuel cell: anode: 6OH-(aq) + 2Al(s) --> 2Al(OH)3 (aq) + 6e- cathode: 3H2O(l) + (3/2)O2(g) + 6e ---> 6OH- (aq) overall: 3H2O(l) + 2Al(s) + (3/2)O2(g) --> 2Al(OH)3 (aq) Ecell = E cathode - E anode = (0.40V) - (-1.66V) = +2.06V All standard reduction half-reactio...
- Sun Mar 14, 2021 8:49 am
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Focus 6 Exercises (53, 57, 73) [ENDORSED]
- Replies: 1
- Views: 52
Re: Focus 6 Exercises (53, 57, 73) [ENDORSED]
6.53 The anode side is the product side (reaction starts with lower concentration product), 0.0010 M CrCl3(aq). Diluting [P] therefore makes Q << 1, which makes ln Q even more negative, and therefore E more positive. Work through the concentration cell example I did in class. Lower concentration pro...
- Sun Mar 14, 2021 7:49 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L.3 Part (d) Question [ENDORSED]
- Replies: 1
- Views: 32
Re: 6L.3 Part (d) Question [ENDORSED]
All half reactions are given in the list of standard reduction potentials. Students do not need to 'know/memorize' the reactions. This makes it much easier and straight forward to figure out the anode (oxidation half-reaction), the cathode (reduction half-reaction), and the overall redox reaction. W...
- Sun Mar 14, 2021 7:34 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6M Exercises (5, 7, 11) [ENDORSED]
- Replies: 2
- Views: 41
Re: 6M Exercises (5, 7, 11) [ENDORSED]
Great answers. Whenever (aq) is given it means water is present and therefore no need to explicitly state H 2 O. When (aq) is stated then that means water is present and can be part of the redox reaction. The oxygen atom in water is 2- oxidation state. The oxygen atom in O2(g) is zero oxidation stat...
- Sun Mar 14, 2021 7:27 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Textbook 6L.7b [ENDORSED]
- Replies: 2
- Views: 58
Re: Textbook 6L.7b [ENDORSED]
Your reaction is not balanced.
- Sun Mar 14, 2021 7:21 am
- Forum: Balancing Redox Reactions
- Topic: balancing redox rxns [ENDORSED]
- Replies: 1
- Views: 83
Re: balancing redox rxns [ENDORSED]
This is a harder one to figure out with the information given. If one was given the cell diagram then straight forward. Ag(s) is the same electrode for anode and cathode. What makes the two half-reactions different are the solutions (electrolytes) the electrodes are in. Ag(s) anode is in contact wit...
- Sat Mar 13, 2021 10:41 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Textbook 7.1 [ENDORSED]
- Replies: 1
- Views: 61
Re: Textbook 7.1 [ENDORSED]
The reason why kinetic control would predominate at low temperatures is because of activation energies. If you look at the graphs that you have, the green line has a lower activation energy barrier. You can think of a lower activation energy as occurring "faster", so as you said, because t...
- Sat Mar 13, 2021 10:33 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Net Ionic Equations? [ENDORSED]
- Replies: 1
- Views: 43
Re: Net Ionic Equations? [ENDORSED]
Yes, when you are writing equilibrium constants, you should be using the net ionic equation!
- Sat Mar 13, 2021 8:10 pm
- Forum: Student Social/Study Group
- Topic: Thank You and Good Luck
- Replies: 1
- Views: 36
Re: Thank You and Good Luck
Thank you and all the best to all my students.
- Sat Mar 13, 2021 6:31 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Difference btwn constant p calorimetry and aconstant v calorimetry [ENDORSED]
- Replies: 1
- Views: 38
Re: Difference btwn constant p calorimetry and aconstant v calorimetry [ENDORSED]
Remember that enthalpy is at constant pressure, so when doing calorimetry at constant pressure, you will be able to find enthalpy values.
- Sat Mar 13, 2021 6:27 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Textbook 7O.1
- Replies: 1
- Views: 42
Re: Textbook 7O.1
Can you let us know which part you need help with, instead of just writing the question. Just so we can have direction. Thanks :)
- Sat Mar 13, 2021 5:48 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cell vs Concentration Cell
- Replies: 4
- Views: 38
Re: Galvanic Cell vs Concentration Cell
A concentration cell is made of two half-cells with the same electrodes but different concentrations of chemical species. This is done in order to create a concentration gradient of electrons wherein an equilibrium is reached through the flow of electrons. Through this flow of electrons, a redox rea...
- Fri Mar 12, 2021 7:11 pm
- Forum: General Rate Laws
- Topic: Lecture 26 [ENDORSED]
- Replies: 1
- Views: 353
Re: Lecture 26 [ENDORSED]
From the balanced chemical equation: unique rate = 1/2 (d[P]/dt) In class I wrote it as the rate of formation of product (d[P]/dt). I could have left it as the unique rate and not multiplied by 2. The most important part is they both match the experimentally determined rate law. The factor of 2 is t...
- Fri Mar 12, 2021 5:22 pm
- Forum: General Rate Laws
- Topic: Intermediate OH- present in overall rate law [ENDORSED]
- Replies: 2
- Views: 26
Re: Intermediate OH- present in overall rate law [ENDORSED]
Water always has HO- and H3O+ present, and therefore can show in rate laws when the reaction rate is pH dependent.
- Fri Mar 12, 2021 2:17 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Advice from a Medical Student [ENDORSED]
- Replies: 234
- Views: 120684
Re: Advice from a Medical Student [ENDORSED]
I wanted to write thank you on here! I keep re-reading this post because it helps me gain back motivation when I feel too defeated and scared about the future as a pre-med student. It’s been a lot of refreshing this page, but hopefully I can get through it! Hi Michelle, I am so glad you found this ...
- Fri Mar 12, 2021 2:08 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Advice from a Medical Student - Part II [ENDORSED]
- Replies: 225
- Views: 18224
Re: Advice from a Medical Student - Part II [ENDORSED]
Hello! I'm Anthony, a first year Neuroscience major. I really appreciate your story and I love people who are trying to help young aspiring people learn and grow. Hi Anthony, thank you so much for the compliment. I hope this is helpful. If you have any questions or need advice moving forward, wheth...
- Fri Mar 12, 2021 12:21 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Kate's Chem 14B Final Review
- Replies: 1
- Views: 81
Kate's Chem 14B Final Review
Hello everyone, I attached my final review worksheet and answer key below. I hope you found these UA sessions helpful and I had so much fun getting to know all of you! Thank you for making me laugh during our sessions and bringing a smile to my face every week. Please say hi in the fall and I know y...
- Thu Mar 11, 2021 8:18 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6N homework problem
- Replies: 1
- Views: 17
Re: 6N homework problem
Please see the solutions manual errors document: https://lavelle.chem.ucla.edu/wp-conten ... rs_7Ed.pdf
- Thu Mar 11, 2021 8:07 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Textbook 6.57 Question about Favorability, choosing Cathode, anode
- Replies: 3
- Views: 30
Re: Textbook 6.57 Question about Favorability, choosing Cathode, anode
Normally if you are determining the cell potential of a Galvanic cell, you want the most positive cell potential. However, in this problem, you are not constructing a Galvanic cell; instead, you are simply trying to find Ka for HF. The K that you find using the Nernst equation is for double the reac...
- Thu Mar 11, 2021 7:45 pm
- Forum: Calculating Work of Expansion
- Topic: W= -PDeltaV
- Replies: 15
- Views: 69
Re: W= -PDeltaV
Use this equation when the volume change is occurring under constant pressure conditions. Since the pressure is constant, it will be irreversible expansion/compression.
- Thu Mar 11, 2021 7:43 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Textbook Question 6.53
- Replies: 2
- Views: 16
Re: Textbook Question 6.53
Remember in a concentration cell, the driving force behind the redox reaction is the difference in concentration between the two cells. The reaction proceeds to equalize the two concentrations, so ions will form on the side with fewer ions to start with (lower CrCl3 concentration). From this informa...
- Thu Mar 11, 2021 6:38 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Potentials as State Functions
- Replies: 1
- Views: 18
Re: Cell Potentials as State Functions
E and E0 are not state functions. They depend on what exactly is oxidized or reduced, which is why you can subtract the reduction potentials for two half-reactions to get cell potential for an overall reaction. However, you cannot add the cell potentials for two overall reactions together to get the...
- Thu Mar 11, 2021 6:28 pm
- Forum: Balancing Redox Reactions
- Topic: Self Test 6K.1A
- Replies: 1
- Views: 23
Re: Self Test 6K.1A
It would be helpful to see what work you already had done in this problem. First write out the reactants and products as given by the problem, unbalanced: Cu + NO3- --> Cu(NO3)2 + NO (we can omit the H+ from HNO3 as it is a spectator ion, remembering that nitric acid is a strong acid which completel...
- Thu Mar 11, 2021 6:19 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Textbook 7.9
- Replies: 1
- Views: 29
Re: Textbook 7.9
In future posts, please include the relevant part of the problem as well. The difference between the two mechanisms is one is dependent on the concentration of H2O while the other is not. When you do the reaction in a dilute solution of sucrose, this means there is a huge amount of water available c...
- Thu Mar 11, 2021 6:11 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L.9
- Replies: 1
- Views: 20
Re: 6L.9
In future posts, please include the relevant part of your question as well. In many cases, you need to go off the reduction reactions given to you. Look up the reduction reactions for each of the species in question, determine which reactions are possible based on the species that the problem tells ...
- Thu Mar 11, 2021 6:10 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: textbook problem 6L.3 (d)
- Replies: 1
- Views: 47
Re: textbook problem 6L.3 (d)
I am not clear on what your question is. Perhaps this past post may help clarify your issue: https://lavelle.chem.ucla.edu/forum/viewtopic.php?t=75817 If you are asking why H+ is not on the products side in the anode half-reaction, think about what is getting oxidized and what it is getting oxidized...
- Thu Mar 11, 2021 5:10 pm
- Forum: Administrative Questions and Class Announcements
- Topic: [CHEM 14B KARAOKE]
- Replies: 68
- Views: 2270
Re: [CHEM 14B KARAOKE]
This was just published: https://www.chemistry.ucla.edu/news/karaoke-fun-%E2%80%9Cdj-lavelle%E2%80%9D Great event, photos, students, … read the article for details. Well Done all Contestants! Many thanks and shout out to event organizers Adila Ahmed, Andre Fabian, Mackenzie Van Valkenburgh, Alette E...
- Thu Mar 11, 2021 5:09 pm
- Forum: Administrative Questions and Class Announcements
- Topic: [KARAOKE UPDATE]
- Replies: 3
- Views: 63
Re: [KARAOKE UPDATE]
This was just published: https://www.chemistry.ucla.edu/news/karaoke-fun-%E2%80%9Cdj-lavelle%E2%80%9D Great event, photos, students, … read the article for details. Well Done all Contestants! Many thanks and shout out to event organizers Adila Ahmed, Andre Fabian, Mackenzie Van Valkenburgh, Alette E...
- Thu Mar 11, 2021 2:13 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Quiz Question
- Replies: 1
- Views: 44
Re: Quiz Question
Because CO2 is the only non solid, the equilibrium expression is Kp=CO2. Use PV=nRT from here to solve.
- Thu Mar 11, 2021 1:50 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Michael's thermochemistry workshop
- Replies: 2
- Views: 51
Re: Michael's thermochemistry workshop
You have the exact right line of reason for this problem! The only mistake that you made is that the problem states that only half of the ice cream gets melted. Therefore, the mass you use when you multiply by deltaHfus should be 125/2 g! However, the first mass you use in the mc(deltaT) term is sti...
- Thu Mar 11, 2021 1:46 pm
- Forum: Calculating Work of Expansion
- Topic: Michael Nguyen
- Replies: 1
- Views: 72
Re: Michael Nguyen
Hi Claire,
Feel free to email me at micngu@ucla.edu if you have a specific question you want to ask me! Also, I have all of my sessions in my Google Drive folder, and you might be able to find what you are looking for in those files as well!
-Michael
Feel free to email me at micngu@ucla.edu if you have a specific question you want to ask me! Also, I have all of my sessions in my Google Drive folder, and you might be able to find what you are looking for in those files as well!
-Michael
- Thu Mar 11, 2021 11:41 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Lecture 26 Question [ENDORSED]
- Replies: 1
- Views: 31
Re: Lecture 26 Question [ENDORSED]
From the balanced chemical equation: unique rate = 1/2 (d[P]/dt) In class I wrote it as the rate of formation of product (d[P]/dt). I could have left it as the unique rate and not multiplied by 2. They both match the experimentally determined rate law. The factor of 2 is the difference between writi...
- Thu Mar 11, 2021 11:08 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Sapling Learning Week 9 and 10 Homework Question 13
- Replies: 1
- Views: 37
Re: Sapling Learning Week 9 and 10 Homework Question 13
Start by writing the slow step rate law, which would be rate=k[HClO][I-]. [HClO] needs to be substituted because intermediates do not belong in the rate law. The first step can be used to achieve this. Write the rate forward and reverse for step 1. Then, rearrange and isolate [HClO]. Substitute this...
- Thu Mar 11, 2021 11:08 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Book 6L.9
- Replies: 1
- Views: 15
Re: Book 6L.9
In order to produce the cell diagram, you need to write the two half reactions. Start with MnO4- to Mn+2, then balance the oxygens, hydrogens, and electrons. The second half reaction is Fe+2 to Fe+3, which only requires the addition of electrons to one side. Coefficients are not necessary in the cel...
- Thu Mar 11, 2021 11:03 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Textbook 6.43 (a)
- Replies: 2
- Views: 15
Re: Textbook 6.43 (a)
Think about this in terms of the equation E= Ecell - RT/nF ln Q. In this way, you can see that Ecell does not change as the reaction proceeds. Whereas, E is related to the equilibrium progression of the reaction through Q.
- Thu Mar 11, 2021 10:01 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Textbook 6.57
- Replies: 1
- Views: 22
Re: Textbook 6.57
The F2 half reaction is given, so you know that this is one of the half reactions. We now need an expression that described HF. Write the HF half reaction in the reduction direction to compare the two reduction potentials and determine which is the anode and which is the cathode.
- Thu Mar 11, 2021 9:58 am
- Forum: General Rate Laws
- Topic: Textbook 7.11A
- Replies: 2
- Views: 18
Re: Textbook 7.11A
Because the rate law is given, write the rate law in different scenarios to determine which step is slow. For example, write if step 1 were slow, step 2 were slow, or step 3 were slow. Then see which matches the proposed rate law.
- Thu Mar 11, 2021 9:56 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: 7.11 Textbook
- Replies: 2
- Views: 16
Re: 7.11 Textbook
The goal is to determine which is the slow step based on the proposed mechanism. Try writing the rate law if step 1 was slow, step 2 was slow, or if step 3 was slow. Then determine which scenario matches the given rate law.
- Thu Mar 11, 2021 9:54 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Week 10 Sapling #13
- Replies: 2
- Views: 36
Re: Week 10 Sapling #13
You are right that HClO is an intermediate. Start by writing the slow step rate law, which would be rate=k[HClO][I-]. [HClO] needs to be substituted because intermediates do not belong in the rate law. The first step can be used to achieve this. Write the rate forward and reverse for step 1. Then, r...
- Thu Mar 11, 2021 8:47 am
- Forum: Administrative Questions and Class Announcements
- Topic: Matthew's notes?
- Replies: 1
- Views: 59
Re: Matthew's notes?
Hi Garmani,
There seemed to be an issue uploading that last night; I think I fixed it now!
-Matt
There seemed to be an issue uploading that last night; I think I fixed it now!
-Matt
- Thu Mar 11, 2021 7:34 am
- Forum: Administrative Questions and Class Announcements
- Topic: Acids and Bases Review- Ty
- Replies: 1
- Views: 114
Acids and Bases Review- Ty
Hi everyone,
Here are the slides I went over in my review session on Tuesday. Hope they help in your studying!
-Ty
Here are the slides I went over in my review session on Tuesday. Hope they help in your studying!
-Ty
- Wed Mar 10, 2021 11:55 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Matthew's Workshop - Week 10
- Replies: 1
- Views: 783
Re: Matthew's Workshop - Week 10
Hi everyone, My session notes/answers are posted! I also included an extra explanation for 4(d) post-workshop using kinetics, so hopefully the answer is doubly clear :). Thank you again for being such amazing students; it's been a pleasure being one of your UAs for the past two quarters. Good luck o...
- Wed Mar 10, 2021 8:47 pm
- Forum: General Rate Laws
- Topic: Final Lecture Clarification
- Replies: 1
- Views: 20
Re: Final Lecture Clarification
In class I wrote it as the rate of formation of product. I could have left it as the unique rate and not multiplied by 2. They both match the experimentally determined rate law. The factor of 2 is the difference between writing the unique rate versus the rate of change of product concentration. K = ...
- Wed Mar 10, 2021 7:13 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Question about Today's Lecture - Why multiply by 2? [ENDORSED]
- Replies: 1
- Views: 236
Re: Question about Today's Lecture - Why multiply by 2? [ENDORSED]
In class I wrote it as the rate of formation of product.
I could have left it as the unique rate and not multiplied by 2.
They both match the experimentally determined rate law.
The factor of 2 is the difference between writing the unique rate versus the rate of change of product concentration.
I could have left it as the unique rate and not multiplied by 2.
They both match the experimentally determined rate law.
The factor of 2 is the difference between writing the unique rate versus the rate of change of product concentration.
- Wed Mar 10, 2021 5:25 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Matthew's Workshop - Week 10
- Replies: 1
- Views: 783
Matthew's Workshop - Week 10
Hi everyone! We've finally made it to Week 10! :D Here's the worksheet for today's session. We will be covering the rest of kinetics, but of course since the final is on Sunday I'll try to have some time to answer questions about any previous material. *Session Work and Answers were posted Thursday ...
- Wed Mar 10, 2021 3:43 pm
- Forum: General Rate Laws
- Topic: intermediates in rate laws
- Replies: 5
- Views: 18
Re: intermediates in rate laws
Typically, the concentration of an intermediate is not something you have control over or even have an ability to measure throughout a reaction. Thus in a rate law, it is not useful to have the concentrations of intermediates. The concentrations of the reactants are what you can control and change i...
- Wed Mar 10, 2021 3:41 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Memorizing an Equation
- Replies: 4
- Views: 41
Re: Memorizing an Equation
This equation can be easily derived from the Arrhenius equation (which is on the formula sheet). k = Ae^{-E_{a}/RT} If you have two different rate constants at two different temperatures for the same reaction, their ratio is given by \frac{k_{2}}{k_{1}} = \frac{Ae^{-E_{a}/RT_{2}}}{Ae^{-E_{a}/RT_{1}}...
- Wed Mar 10, 2021 3:28 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 6D.15
- Replies: 2
- Views: 25
Re: 6D.15
Correct- to solve these problems, you will need to refer to the table to find the K a or K b values. In this case specifically, for something like NH 4 Cl, this is actually a salt of NH 4 + and Cl - . Thus you'll have to look up the K a of NH 4 + , but you won't actually find this in the table. You ...
- Wed Mar 10, 2021 11:58 am
- Forum: Administrative Questions and Class Announcements
- Topic: Acid and Base Review (Julia's Step-Up Session)
- Replies: 1
- Views: 98
Acid and Base Review (Julia's Step-Up Session)
Hello! As requested, I have attached the answer key from today's review on acids and bases. The link to the worksheet is also included in the beginning of the document. Please let me know if you have any questions about the worksheet. I wish you all the best on the final and the rest of your classes...
- Wed Mar 10, 2021 11:54 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Pre-equilibrium approach [ENDORSED]
- Replies: 3
- Views: 26
Re: Pre-equilibrium approach [ENDORSED]
If the 1st step is slow then no need for any approximation. Rate law won't have intermediate in it.
- Wed Mar 10, 2021 11:52 am
- Forum: General Rate Laws
- Topic: Textbook Question 7A. 17
- Replies: 4
- Views: 23
Re: Textbook Question 7A. 17
You can use experiments 1 and 3 to find that the reaction is second order with respect to B. When you compare the rate law expressions of the two experiments, you end up simplifying it to 0.4139^n = 0.171. You can then solve for n by taking the log of both sides to get nlog(0.4139) = 0.171, which ge...
- Wed Mar 10, 2021 11:52 am
- Forum: Experimental Details
- Topic: Fast step at equilibrium [ENDORSED]
- Replies: 4
- Views: 53
Re: Fast step at equilibrium [ENDORSED]
As I discussed in class step 2 is slow. Therefore product formed in step 1 builds up. Product can go back to reactant in step 1. Since forward and reverse reactions are occurring and step 1 is treated as approximately at equilibrium.
- Wed Mar 10, 2021 11:46 am
- Forum: General Rate Laws
- Topic: textbook problem 7.A. 15 part a
- Replies: 4
- Views: 21
Re: textbook problem 7.A. 15 part a
If you compare experiments 1 and 4, you'll find that the reaction is 0th order with respect to C. This means that when solving for the rest of the reaction orders, we can omit C because the concentrations of C will just equal 1.
Hope this helps!
Hope this helps!
- Wed Mar 10, 2021 11:17 am
- Forum: Administrative Questions and Class Announcements
- Topic: Suggestion for future
- Replies: 1
- Views: 43
Re: Suggestion for future
Thanks for the useful suggestion. Note that the UAs did do review the week of midterm 1, the week of midterm 2, and the week of the final. So those three weeks do a lot of review. There are pros and cons. Some students cannot attend specific times covering review of topic X. They then request that t...
- Wed Mar 10, 2021 11:01 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: textbook 6N.3 [ENDORSED]
- Replies: 2
- Views: 88
Re: textbook 6N.3 [ENDORSED]
I had questions for parts (a) and (c). The problem states: Predict the potential of each of the following cells: (a) Pt(s)|H2(g, 1.0 bar)|HCl(aq, 0.075 mol/L)||HCl(aq, 1.0 mol/L)|H2(g, 1.0 bar)|Pt(s) For this one, when finding the standard potential first, does the Cl in HCl not matter and that's w...
- Wed Mar 10, 2021 11:00 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Writing Out Cell Diagrams
- Replies: 3
- Views: 35
Re: Writing Out Cell Diagrams
An inert conductive electrode (such as Pt) must be added to a cell when there is no other way of conducting electrons. Electrons need to get from one side of the cell to the other, and this is done by first conducting through one electrode, then the wire, then conducting through the other electrode....
- Wed Mar 10, 2021 10:44 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Is there a catalyst in this mechanism? [ENDORSED]
- Replies: 6
- Views: 67
Re: Is there a catalyst in this mechanism? [ENDORSED]
Thanks. I wanted to check question was correct.
Yes water is the catalyst in this reaction.
Without water the reaction does not occur.
Yes water is the catalyst in this reaction.
Without water the reaction does not occur.
- Wed Mar 10, 2021 10:38 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Focus Problem 7.21
- Replies: 2
- Views: 21
Re: Focus Problem 7.21
(f) initial rate against [A] for a reaction that is 1st order in A = a graph that shows how initial rate of a reaction varies with different values of [A]. The corresponding formula would be rate = k[A]^1, which k being a constant. [A] is raised to the first because it is a first order reaction. Thi...
- Wed Mar 10, 2021 10:32 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Focus Problem 7.11 [ENDORSED]
- Replies: 1
- Views: 50
Re: Focus Problem 7.11 [ENDORSED]
Step 1 cannot be the slow step as it does not match the given rate law.
Therefore, look at next step.
In Step 2 one needs to substitute out the intermediate, and when you do it matches the given rate law.
Answer is Step 2 is the slow step.
I will do a very similar example today in class.
Therefore, look at next step.
In Step 2 one needs to substitute out the intermediate, and when you do it matches the given rate law.
Answer is Step 2 is the slow step.
I will do a very similar example today in class.
- Wed Mar 10, 2021 10:24 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Textbook 7D.5 [ENDORSED]
- Replies: 1
- Views: 21
Re: Textbook 7D.5 [ENDORSED]
It can solved using either ratio.
- Wed Mar 10, 2021 10:15 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Is there a catalyst in this mechanism? [ENDORSED]
- Replies: 6
- Views: 67
Re: Is there a catalyst in this mechanism? [ENDORSED]
Which problem is this?
- Wed Mar 10, 2021 10:05 am
- Forum: First Order Reactions
- Topic: Sapling Week 9/10 #11, Part 2 [ENDORSED]
- Replies: 3
- Views: 64
Re: Sapling Week 9/10 #11, Part 2 [ENDORSED]
Thanks Sid.
Good Chemistry.
:-)
Good Chemistry.
:-)
- Wed Mar 10, 2021 10:01 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Initial Rates = Maximum rates [ENDORSED]
- Replies: 9
- Views: 125
Re: Initial Rates = Maximum rates [ENDORSED]
Good answers. Good Chemistry. :-)
- Wed Mar 10, 2021 9:54 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Reaction Intermediates? [ENDORSED]
- Replies: 4
- Views: 49
Re: Reaction Intermediates? [ENDORSED]
Intermediates are species that are in the mechanism, but not in the overall rate law. The way to distinguish intermediates and catalysts is that intermediates are always produced by a reaction, and then consumed immediately after in the next reaction. On the other hand, catalysts are consumed first...
- Wed Mar 10, 2021 7:36 am
- Forum: Administrative Questions and Class Announcements
- Topic: trick
- Replies: 6
- Views: 104
Re: trick
Click on chem_mod post number and you can see all chem_mod posts.
- Wed Mar 10, 2021 7:28 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Exergonic vs Exothermic [ENDORSED]
- Replies: 4
- Views: 64
Re: Exergonic vs Exothermic [ENDORSED]
Exergonic and endergonic usually refer to Gibbs free energy. Endothermic & exothermic refer to enthalpy. I remember it because exergonic & endergonic have "g" like Gibbs while endothermic & exothermic have "th" like enthalpy. Good one. Thanks for sharing. I should us...
- Wed Mar 10, 2021 7:08 am
- Forum: Administrative Questions and Class Announcements
- Topic: [CHEM 14B KARAOKE]
- Replies: 68
- Views: 2270
Re: [CHEM 14B KARAOKE]
Well Done!