Search found 131 matches
- Mon Mar 15, 2021 12:31 pm
- Forum: Student Social/Study Group
- Topic: Favorite Chemistry YouTube Channels
- Replies: 39
- Views: 3482
Re: Favorite Chemistry YouTube Channels
What are your favorite YouTubers/channels for reviewing chemistry? Thought making a thread like this would be very helpful for everyone studying for finals :)) Some of my favorites are CrashCourse and Professor Dave Explains! Hands down, organic chemistry tutor. He is a UCLA alumni too sooooo <3 Ju...
- Mon Mar 15, 2021 12:29 pm
- Forum: Student Social/Study Group
- Topic: Anxiety
- Replies: 109
- Views: 7930
Re: Anxiety
Algernon Jackson 2l wrote:How are you guys coping with the anxiety that this class causes?
WE FINISHED!! i hope the class didn't hurt you guys too much <3 Good job this quarter !
- Mon Mar 15, 2021 12:29 pm
- Forum: Administrative Questions and Class Announcements
- Topic: CHEM COMMUNITY SCORES
- Replies: 16
- Views: 1392
Re: CHEM COMMUNITY SCORES
JTieu_1L wrote:Are chem community scores additive, meaning the scores are based on how many posts total?
I think its additive! Bc by week 7 I already had 50/50 chem points on CCLE :))
- Fri Mar 12, 2021 10:51 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Intermediates and Catalyst Summary
- Replies: 2
- Views: 191
Intermediates and Catalyst Summary
Hey guys, I'm trying to understand [still] when intermediates and catalyst are present in elementary step rate laws and overall rate laws. So you can include intermediates and catalysts in elementary step rate laws. But you can not include catalyst and intermediates in overall rate law unless they a...
- Fri Mar 12, 2021 10:05 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Are catalysts consumed?
- Replies: 37
- Views: 1860
Re: Are catalysts consumed?
Hi! I'm very confused on whether catalysts are actually consumed in a reaction or not. In lecture and in a post on Chemistry Community, Dr. Lavelle said that catalysts are consumed first in a reaction, and then are produced. However, there was a question in the textbook that said catalysts are neve...
- Fri Mar 12, 2021 10:03 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Missed Chem Community Points
- Replies: 13
- Views: 1227
Re: Missed Chem Community Points
I didn't do last weeks chemistry community posts, does anyone know how many points I will be losing and if there is any way to make them up? Thank you You should be losing 5 pts, however, I would do 10 this week just in case overall is counter instead of per week. I think this is the case bc I post...
- Fri Mar 12, 2021 10:02 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Catalyst
- Replies: 30
- Views: 2144
Re: Catalyst
Do not include catalyst in overall rate. You can include intermediates in elementary steps but not in the overall rate, I'm pretty sure!
- Fri Mar 12, 2021 6:37 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Intermediates in overall rate law
- Replies: 3
- Views: 363
Intermediates in overall rate law
Hey guys, I know that intermediates can be used to elementary rate laws and I thought we weren't supposed to involve them in the overall rate law, but in a video I was watching (https://www.youtube.com/watch?v=4czm7qIbUjA) the guy involved the intermediate in the overall rate law. Can the intermedia...
- Thu Mar 11, 2021 5:14 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Reducing/Oxidizing Agent
- Replies: 4
- Views: 269
Re: Reducing/Oxidizing Agent
How do you identify reducing and oxidizing agents from a redox reaction/half reactions? I'm having trouble knowing which species in the anode/cathode reaction it is. Thanks! The species in the half rxn that is oxidized, is the reducing agent Ex: Sn^2+ -> Sn^4+ +2e- In this case, the Sn^2+ is the re...
- Mon Mar 08, 2021 8:38 am
- Forum: Balancing Redox Reactions
- Topic: Sapling #4 Week 7-8 Question
- Replies: 1
- Views: 150
Sapling #4 Week 7-8 Question
Hey guys can someone explain to me why we exclude H+ in both the HNO3 and the HAuCl4 in problem 4 in week 7-8 sapling? I understand the rest, but I was just confused on why we exclude the H+, thank you.
- Sun Mar 07, 2021 3:07 pm
- Forum: Student Social/Study Group
- Topic: How do you deal with burnout?
- Replies: 144
- Views: 15931
Re: How do you deal with burnout?
This quarter has been pretty tough and I have been in burnout for the majority of it. How do you guys deal with burnout and how do you regain your motivation to do work? Just try your best. I just tell myself "Come on, Grace. You just have to pass to graduate come onnnnn". But if you're p...
- Sun Mar 07, 2021 3:04 pm
- Forum: Administrative Questions and Class Announcements
- Topic: week 10 lectures?
- Replies: 15
- Views: 912
Re: week 10 lectures?
connie ma 3G wrote:are we gonna have lectures all throughout week 10 (on MWF) or are we ending early? just wondering cuz im currently super behind on watching lectures haha.
I'm pretty sure lectures are ending this Wednesday!! You should catch up asap :))
- Sun Mar 07, 2021 3:04 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidizing Agent
- Replies: 33
- Views: 1325
Re: Oxidizing Agent
The higher (more +) the reduction potential of a species, the better oxidizing agent it is.
- Sun Mar 07, 2021 3:01 pm
- Forum: Zero Order Reactions
- Topic: Overall order of the reaction
- Replies: 45
- Views: 2012
Re: Overall order of the reaction
KMcFarland_2L wrote:How do you determine the overall order of a reaction?
You can't tell from just looking at the rxn equation, so you have to take the sum of the order of the individual reactants and that will be the order of the products.
- Sun Mar 07, 2021 2:59 pm
- Forum: Zero Order Reactions
- Topic: Half life
- Replies: 20
- Views: 1030
Re: Half life
Fdonovan 3D wrote:How do you calculate the half life of a zero order rxn?
Dr. Lavelle gave us the equation in class. It is t1/2=[A]0/2k for the half life of a zero order rxn.
- Thu Feb 25, 2021 11:53 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 30
- Views: 1426
Re: Salt Bridge
Michael Iter 2F wrote:Hi, can someone explain to me the purpose of the salt bridge? What happens if we don't have it?
It neutralized both the cathode/where reduction is occurring and anode/where oxidation is occurring.
- Wed Feb 24, 2021 10:33 am
- Forum: Administrative Questions and Class Announcements
- Topic: Chemistry Community Deadlines
- Replies: 11
- Views: 1067
Re: Chemistry Community Deadlines
On CCLE, is your guys' saying you do not have the full 100% in Chem Community because we're only on week 8? I'm not sure if I should be concerned or just wait till the end of the quarter and hopefully it will update to 100% with all the points... Hmmm I already posted more than 50 times this quarte...
- Wed Feb 24, 2021 10:31 am
- Forum: Student Social/Study Group
- Topic: Fave food
- Replies: 266
- Views: 40094
Re: Fave food
Kristine_Aramyan_3K wrote:what's your fave food/snack/dessert? i'm personally craving banana bread rn
I really like mac n cheese especially after an exam or something stressful ehehehe butttt my fav snack is probably fresh mangooo is big yummyyy
- Wed Feb 24, 2021 10:30 am
- Forum: Balancing Redox Reactions
- Topic: Oxidizing vs Reducing
- Replies: 55
- Views: 2605
Re: Oxidizing vs Reducing
Sean Phen wrote:What are some good rules to remember which is the oxidizing agent and which is the reducing agent?
https://www.youtube.com/watch?v=dF5lB7gRtcA
This video is very helpful to understanding redox rxns if you're a visual learner! TOCT is very good at explaining alot of CHEM 14B topics!
- Wed Feb 24, 2021 10:29 am
- Forum: Administrative Questions and Class Announcements
- Topic: Chem community points
- Replies: 15
- Views: 700
Re: Chem community points
Does anyone know if we'll do what we did last quarter in 14a with points where it won't be counted per week but as long as you have 50 total? I think so! I already posted by 60 times or something and I already have 50/50 in that category on Ccle! Just in case though, you should still do your 5 post...
- Wed Feb 24, 2021 10:26 am
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm 2 score release
- Replies: 13
- Views: 903
Re: Midterm 2 score release
I think either tonight [wed.] or tomorrow [thurs.]! Just like last time if I had to guess.
- Wed Feb 24, 2021 8:23 am
- Forum: Balancing Redox Reactions
- Topic: Sapling Week 7/8 #1
- Replies: 10
- Views: 2066
Re: Sapling Week 7/8 #1
Also, if you're a visual learner, this video is very good [like most of TOCT's vids] at explaining how to calculate oxidation numbers.
https://www.youtube.com/watch?v=j0hI-a6EWWo
https://www.youtube.com/watch?v=j0hI-a6EWWo
- Sun Feb 21, 2021 12:27 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: deltaU=deltaH+w
- Replies: 8
- Views: 674
Re: deltaU=deltaH+w
Wasila Sun 2I wrote:Under what circumstances can we use the delta U=delta H+ w equation? Like what allows delta H to be interchangeable with q?
Must be in constant pressure and a open or closed system.
- Fri Feb 19, 2021 3:34 pm
- Forum: Student Social/Study Group
- Topic: Classes for next quarter?
- Replies: 165
- Views: 16429
Re: Classes for next quarter?
I'm debating if I want to take Chem 14C and Chem 14BL at the same time, because I also have two other classes that I want to take (LS 7B and one more that I'm undecided on). I might end up taking Chem 14BL fall quarter though. Not sure what is the best choice Heyyyyy! I'm taking chem14bl and chem14...
- Fri Feb 19, 2021 3:34 pm
- Forum: Calculating Work of Expansion
- Topic: unit of w
- Replies: 17
- Views: 1241
Re: unit of w
The units are kj or J! If you solve it in L.atm, convert it into J by multiplying it by 101.325. Once it's in J, divide by 1000 to convert it into kj. Hope this helps :)
- Fri Feb 19, 2021 3:32 pm
- Forum: Calculating Work of Expansion
- Topic: Value of Q
- Replies: 20
- Views: 1014
Re: Value of Q
Q is the quotient reactant that we learned for and before Midterm 1! It is [P]/[R] like K but NOT at equilibrium. To compare Q and K use le chatelier's princple: Q<K; will shift to products so -DeltaG and spontaneous Q=K; equilibrium Q>K; will shift to reactants so +DeltaG and spontaneous in the rev...
- Fri Feb 19, 2021 3:30 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Is thermal mugs an example of an isolated system?
- Replies: 38
- Views: 2106
Re: Is thermal mugs an example of an isolated system?
Yes! No heat/energy or matter can enter or exit the system in the mug so it is an isolated system :) unless you open it! Then it would be an open system.
- Fri Feb 19, 2021 3:29 pm
- Forum: Calculating Work of Expansion
- Topic: Work sign
- Replies: 46
- Views: 2106
Re: Work sign
When a gas is doing work, it is a -w. When the surroundings are doing work on a system, it is +w because the system is gaining work.
- Fri Feb 19, 2021 3:28 pm
- Forum: Student Social/Study Group
- Topic: Post Midterm 2 De-stressing
- Replies: 92
- Views: 7328
Re: Post Midterm 2 De-stressing
I finished it at 12 pm today!! Afterwards I played videogames till now so likkee 3 hours ;w; , treat yourself afterwards!! you deserve it! @everyone reading this <3
- Tue Feb 16, 2021 6:01 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: DeltaU and Isothermic Reversible and Irreversible reactions
- Replies: 1
- Views: 129
DeltaU and Isothermic Reversible and Irreversible reactions
Hey guys, In lecture Lavelle said that deltaU= 0 and therefore, q = -w can apply to both isothermic reversible and irreversible pathways. In what scenerios is this true (like constant pressure, volume, etc) ? Or is it always true? I understand why deltaU=0 for isothermic rev. rxns but not for irreve...
- Mon Feb 15, 2021 9:34 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Textbook problem 4J.13
- Replies: 2
- Views: 142
Textbook problem 4J.13
Hey guys, can someone explain the relationship between stability [in respect to elements] with a + or - deltaG? I don't understand how a -DeltaG is stable with respect to elements and a +DeltaG is not.
Thank you!
Thank you!
- Mon Feb 15, 2021 10:58 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: DeltaS total = 0 for reversible reactions
- Replies: 2
- Views: 203
DeltaS total = 0 for reversible reactions
Hello, fellas
Can someone explain why DeltaS total = 0 for reversible reactions and DeltaS total > 0 for irreversible reactions? I can't seem to conceptually understand this :(.
Is it because in a reversible rxn, the Pex and Pint are in equilibrium?
Thank you!
Can someone explain why DeltaS total = 0 for reversible reactions and DeltaS total > 0 for irreversible reactions? I can't seem to conceptually understand this :(.
Is it because in a reversible rxn, the Pex and Pint are in equilibrium?
Thank you!
- Sat Feb 13, 2021 4:42 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Reversible Pathway
- Replies: 2
- Views: 210
Reversible Pathway
Are all reversible rxns isothermic? If the temperature stays constant (a aspect of a reversible rxn), would all reversible rxns be isothermic? If no, can you explain a scenario?
Thank you :>
Thank you :>
- Fri Feb 12, 2021 2:57 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: First Law of Thermo Question
- Replies: 6
- Views: 354
First Law of Thermo Question
Hey guys, I just wanted to know if deltaU=q+w is only applicable to closed systems or also open systems? In a class problem, he used this relationship with a open system but the definition says for closed system so I just want to make sure.
Thank you :>
Thank you :>
- Thu Feb 11, 2021 7:30 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Can We Review our Exams?
- Replies: 69
- Views: 3391
Re: Can We Review our Exams?
Hi, I was wondering if anyone knows if there is any way that we can review our midterm once the midterm scores are out? I would like to know what questions I got correct and incorrect to help me prepare for the cumulative final. I'm sure if you ask your TA during their office hours they will go ove...
- Thu Feb 11, 2021 9:13 am
- Forum: Student Social/Study Group
- Topic: Points needed to pass?
- Replies: 76
- Views: 7945
Re: Points needed to pass?
kateraelDis1L wrote:Hi, I am wondering how many points are needed (or how many we can miss) in 14B in order to end with a B? B-? C+? C? and C- ? Idk how to do the calculations so if someone has figured it out I'd love to know.
Thanks in advance ;)
You only need a 50% (200/400) to pass the class with a C- :>
- Thu Feb 11, 2021 9:11 am
- Forum: Administrative Questions and Class Announcements
- Topic: cc update
- Replies: 23
- Views: 1231
Re: cc update
Has chem community been updated since grades were last put in mid week 5? Just wondering because mine still doesn't reflect an accurate count and I'm wondering if I should reach out to my TA at this point or continue to wait it out. I think Lavelle does them in intervals so he'll fix it next time h...
- Thu Feb 11, 2021 9:10 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Different R Constants
- Replies: 14
- Views: 768
Re: Different R Constants
I am confused on when to use which value for the gas constant: R = 8.3145 J/mol·K. and R= 0.08204 liter·atm/mol·K. Can anyone help? It depends on what you're calculating. Best way to find out what you have to use is looking at the units and seeing if they cancel out with whats given to what you wan...
- Thu Feb 11, 2021 9:07 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Free Energy
- Replies: 49
- Views: 2122
Re: Free Energy
Melissa Solis 1H wrote:Can someone explain what a state function is again and why free energy is a state function?
For a state function, the path you took to get the your values does not matter so you can only take into consideration your final and initial values.
- Thu Feb 11, 2021 9:06 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Textbook problem 5.55
- Replies: 1
- Views: 78
Textbook problem 5.55
Hi guys, can anyone explain the textbook problem 5.55 explanation for part a ? I understand how to find K but I'm having a hard time understanding the explanation for part a. The equation: A reaction used in the production of gaseous fuels from coal, which is mainly carbon, is C(s)+H2O(g)⇌CO(g)+H2(g...
- Wed Feb 03, 2021 8:09 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Tips for Concentrating during a test
- Replies: 31
- Views: 1324
Re: Tips for Concentrating during a test
Clean work area, try your best to not look at the clock on respondus [force yourself to focus], I like to write the components I need to solve the problem on my scratch work and write very organized [makes me feel like Ik what im doing], MAKE SURE YOU EAT WELL BEFORE EXAM, use the bathroom before th...
- Wed Feb 03, 2021 8:04 pm
- Forum: General Science Questions
- Topic: Midterm 1
- Replies: 4
- Views: 317
Re: Midterm 1
Hi guys im panicking to the point of depression. I did so so bad on the exam. When I saw that the class average was so high, I almost died because I did so bad. For those who are successful this quarter, how are you guys staying successful? I was successful in 14A by doing the textbook practice pro...
- Wed Feb 03, 2021 7:52 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Can We Review our Exams?
- Replies: 69
- Views: 3391
Re: Can We Review our Exams?
I'm sure if you ask your TA they will let you see what you got wrong and you may be able to review/ask them!
- Wed Feb 03, 2021 6:17 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Double Checking
- Replies: 2
- Views: 138
Re: Double Checking
Melissa Solis 1H wrote:During lecture today (2/3) prof. Lavelle was explaining that U is at equilibrium/ equal to zero when it's at the minimum of the reaction and for entropy, it's at equilibrium when it's at the maximum, right?
Yes! You are correct. Entropy [S] and Degeneracy [M] are maximum while U is minimum [0].
- Wed Feb 03, 2021 6:14 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Grades for Chemistry Community
- Replies: 21
- Views: 866
Re: Grades for Chemistry Community
Hi, Right now, I have a 21/25 for Chemistry Community posts. However, shouldn't we have a minimum of 20 posts since we have not completed week 5 yet? I am just making sure I didn't miss anything. They are most likely grading on how many posts/responses you have atm! It will most likely change later...
- Wed Feb 03, 2021 6:13 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Units
- Replies: 11
- Views: 419
Re: Units
hi, I would just like some clarification as to what the unit should be for specific heat (more specifically regarding the temperature unit)? I noticed in lecture Professor Lavelle mentioned both Celsius and Kelvin, and it seemed interchangeable. J/gºC or J/g K. I think both are fine but I would use...
- Wed Feb 03, 2021 6:12 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Do CC work for bruin cast videos
- Replies: 6
- Views: 268
Re: Do CC work for bruin cast videos
Whenever I'm watching a lecture or video, I usually like to have subtitles on as well to help me follow along. Whenever I try to turn them on through the button on the video they don't actually show up. Has it worked for anyone else? I don't have CC either and it makes lecture following a long a li...
- Tue Feb 02, 2021 11:56 am
- Forum: Calculating Work of Expansion
- Topic: What is V1 and V2
- Replies: 12
- Views: 774
Re: What is V1 and V2
When solving for the work of expansion, the equation uses the integral from V1 to V2. Are these values the initial volume of the container and then the final volume of the container after expansion? if you want to read more on this it's on 4A.3: Expansion work in the textbook. It explains V1 (initi...
- Mon Feb 01, 2021 3:27 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Week 5 Question
- Replies: 3
- Views: 170
Week 5 Question
Just to clarify, will we be going over outlines 3 and 4 during this week? I kind of got confused because of last week's midterm, but I'm sure last week we went over outlines 3 and this week is beginning to enter week 4.
I just want to know so I can catch up on reading :) ty
I just want to know so I can catch up on reading :) ty
- Sat Jan 30, 2021 7:53 pm
- Forum: Student Social/Study Group
- Topic: Go treat yourself after MT1!
- Replies: 75
- Views: 5296
Re: Go treat yourself after MT1!
I took a 3 hour nap after!! Self care <3 I hope you and anyone reading this enjoyed the rest of friday after the exam! <3 keep trying u can do!
- Sat Jan 30, 2021 10:22 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: percent protonation/deprotonation
- Replies: 15
- Views: 889
Re: percent protonation/deprotonation
Nina Fukui 2J wrote:What are the differences between the two???
percent protonation/deprotonation
% deprotonation = used for acids bc acids deprotonate [give off H+]
% protonation = used for bases bc bases protonate [take H+]
Calculated a similar way, but describes either acids or bases.
- Sat Jan 30, 2021 10:19 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Memorize bond enthalpies / standard enthalpies of formation?
- Replies: 39
- Views: 1385
Re: Memorize bond enthalpies / standard enthalpies of formation?
samanthaywu wrote:Will we need to have memorized any common bond enthalpies and standard enthalpies of formation or will we always be provided a table when this information is needed?
Nope! They should be given on exams. :)
- Fri Jan 29, 2021 12:11 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Grades
- Replies: 13
- Views: 791
Midterm Grades
Hey guys! I hope the midterm treated you well and I hope this is the right place to ask this, but I just wanted to know when we can expect midterm grades? It was multiple choice so I was expecting to see the results right after lol.
Thank you!
Thank you!
- Thu Jan 28, 2021 11:03 am
- Forum: Identifying Acidic & Basic Salts
- Topic: Will buffer solutions be on the midterm?
- Replies: 4
- Views: 416
Will buffer solutions be on the midterm?
Hey guys,
One TA told me buffer solutions would be on tomorrow's midterm and another one told me it won't be on it. Im a little confused. Does anyone know?
One TA told me buffer solutions would be on tomorrow's midterm and another one told me it won't be on it. Im a little confused. Does anyone know?
- Mon Jan 25, 2021 5:04 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Question 5I.13 (C)
- Replies: 3
- Views: 256
Question 5I.13 (C)
Hey guys,
Can someone explain why Cl2 is more stable than F2? The answer book says because it has a larger K, so because it's [P]/[R] is larger? Is it because there's more products than reactants?
Thank you!
Can someone explain why Cl2 is more stable than F2? The answer book says because it has a larger K, so because it's [P]/[R] is larger? Is it because there's more products than reactants?
Thank you!
- Sun Jan 24, 2021 1:34 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Should we memorize any standard states?
- Replies: 3
- Views: 193
Should we memorize any standard states?
Should we memorize any standard states for Friday's midterm?
So far, I only know that carbon's standard state is graphite and water's is liquid.
I'm not sure if we should know others, so I was wondering what you guys thought. Thanks ! :)
So far, I only know that carbon's standard state is graphite and water's is liquid.
I'm not sure if we should know others, so I was wondering what you guys thought. Thanks ! :)
- Sat Jan 23, 2021 1:11 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm 1 Allowed Materials and Procedure
- Replies: 6
- Views: 338
Re: Midterm 1 Allowed Materials and Procedure
What I heard from my TA was that we will join our discussion sections on our phone and then will take the exam using respondus. In terms of allowed materials, just print out the periodic table, equation/constants sheet from the course website and bring a calculator. Do you know if it will be respon...
- Fri Jan 22, 2021 6:23 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Increasing pressure
- Replies: 23
- Views: 948
Re: Increasing pressure
IreneSeo3F wrote:Can someone explain why the concentration of the reactants and products remain the same when inert gas is added?
Inert gases do not affect the rxn [non-reactive gas] so they will not affect the K value.
- Fri Jan 22, 2021 6:21 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: R values
- Replies: 9
- Views: 267
Re: R values
I’ve been seeing that there are two R values (0.0821 atm•L/mol•K and 8.3145 J⋅K−1⋅mol−1) and I’m just wondering how we know when to use which one? Thanks! It depends what you are given in the problem; bars or atm. In lavelle's equation and constant sheet, both forms are given so just choose to mat...
- Fri Jan 22, 2021 6:19 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Preferred way to calculate enthalpy
- Replies: 6
- Views: 402
Re: Preferred way to calculate enthalpy
Hi, so I understand that there are three methods to calculating enthalpy changes: Hess's Law, Bond Enthalpy, and Standard Enthalpy, and that bond enthalpy is usually the most inaccurate, but is there a specific situation where we should use Hess's law or standard enthalpy? Is one more accurate than...
- Fri Jan 22, 2021 4:36 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Textbook problem 4D.23
- Replies: 1
- Views: 119
Textbook problem 4D.23
Hey guys, I just wanted to make sure I'm understanding how to find standard enthalpies of formation correctly. The problem is: Calculate the standard enthalpy of formation of dinitrogen pentoxide from the following data: 2NO(g)+O2(g)→2NO2(g); ΔHo=-114.1 kJ 4NO2(g)+O2(g)→2N2O5(g); ΔHo=−110.2kJ and fr...
- Thu Jan 21, 2021 7:54 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Sapling Week 2 #5 Explanation
- Replies: 5
- Views: 267
Re: Sapling Week 2 #5 Explanation
you add [BH+] to [B] because when you solved for x, that x didn't include the concentration that was protonated. The whole thing would be your initial concentration. Oh, I see. So does this only occur when calculating the % protonated for a base? I know % ionized/dissociated for an acid, you only c...
- Thu Jan 21, 2021 7:38 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Sapling Week 2 #5 Explanation
- Replies: 5
- Views: 267
Sapling Week 2 #5 Explanation
Hi guys, I was wondering if someone could explain why, in week 2's #5 in Sapling, the formal value of [B] includes the sum of [B] and [BH+]? The formal concentration of B is the sum of the concentrations of B and BH+. % amine protonated=[BH+]/[BH+]+[B]×100=4.95×10−5 M4.95×10−5 M+0.000119 M×100%=29.5...
- Sat Jan 16, 2021 7:09 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Identifying Acids, Bases, and salts
- Replies: 8
- Views: 535
Identifying Acids, Bases, and salts
Hey guys, I'm having a difficult time understanding how to identify acids, bases, and if a salt is acidic, basic or neutral (kind of hard when you mistake a base for an acid, ahaha). Do you guys have any tips in trying to distinguish a acid from a base without being given the equation? For example, ...
- Thu Jan 14, 2021 9:14 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Difference between pH and pOH
- Replies: 12
- Views: 1182
Re: Difference between pH and pOH
Hey guys! I was wondering if anyone could explain the conceptual difference between pH, pOH, Kb, and pKb? Thanks in advance! Ph = -log (concentration of H3O+) POH= -log(concentration of OH-) Kb = basicity constant or base ionization constant, solved same was as K = [P]/[R] pKb= -log Kb Strength of ...
- Thu Jan 14, 2021 9:11 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: What is the Conjugate Seesaw
- Replies: 11
- Views: 724
Re: What is the Conjugate Seesaw
Can someone explain this idea of the conjugate seesaw? I don't really remember learning this before, but I'm curious what it is because it sounds interesting! Here are the rules between Acids/Bases and Conjugate Acids/Bases or the conjugate seesaw: If strong acid, then weak conjugate base If weak a...
- Wed Jan 13, 2021 8:22 pm
- Forum: General Science Questions
- Topic: Acid & Base Equilibria Lecture Question
- Replies: 7
- Views: 371
Re: Acid & Base Equilibria Lecture Question
Hiya, I am slightly confused on the autoprotolysis reaction's equilibrium constant from lecture. Why is [H20] removed from Kc = \frac{[H_{3}O^{+}][OH^{+}]}{[H_{2}O]^{2}} ? Professor Lavelle mentioned that the concentration of [H2O] is the same on the left and the right of the reaction, which is why...
- Wed Jan 13, 2021 8:19 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Getting two positive x values when using quadratic
- Replies: 43
- Views: 4845
Re: Getting two positive x values when using quadratic
Hi, so from lecture, Dr. Lavelle talks about how we use the quadratic formula to solve for the x change value in ICE tables, and then proceeds to show how we omit the negative x value and use the positive one. What happens when we get two positive x values? Would we test both x values into the ICE ...
- Wed Jan 13, 2021 7:09 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Pressure vs. concentration
- Replies: 9
- Views: 273
Re: Pressure vs. concentration
How do you know whether to write K for a gas as for example PCl2/PBr2 or [Cl2]/[Br2] It also depends what you are given, if you are given Moles (M) and Litres (L) then it is Kc or concentration. If you are given bars or atm, then it is Kp or partial pressure. I am sure Dr. Lavelle will specify in e...
- Wed Jan 06, 2021 7:45 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Equilibrium Constant in Le Chatelier's
- Replies: 3
- Views: 172
Re: Equilibrium Constant in Le Chatelier's
Just to clarify, any stresses that result in a change in accordance with le Chatelier's rule do NOT affect the value of the equilibrium constant other than temperature right? So any change in pressure or concentration still cause the equilibrium constant to remain the same value despite the change ...
- Wed Jan 06, 2021 7:42 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Will adding a solid reactant increase the amount of product?
- Replies: 6
- Views: 1436
Re: Will adding a solid reactant increase the amount of product?
Okay, that definitely makes sense. I was a bit confused because I knew that the amount of reactants in general would change, but at the same time the actual value of K doesn't take solids into account. However, it makes sense that having more reactants would ultimately lead to increased products, e...
- Wed Jan 06, 2021 7:22 pm
- Forum: Ideal Gases
- Topic: Ideal gas law and reverse reactions
- Replies: 5
- Views: 201
Re: Ideal gas law and reverse reactions
Does the ideal gas law still follow the general rule of reverse reactions wherein the equilibrium constant for an equilibrium written in one direction is the reciprocal of the equilibrium in the opposite direction since the ideal gas law is a bit more complex (accounting for the differences of stoi...
- Wed Jan 06, 2021 7:20 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Sapling Homework
- Replies: 6
- Views: 307
Sapling Homework
Sorry guys, I don't know where to post this question so I'm putting it here! I took Chem 14A fall '20 and a couple of things have changed since then. We used to turn in textbook problems to our TAs but I think that was substituted with Sapling homework. Is the only homework the one on Sapling due Su...
- Tue Jan 05, 2021 7:32 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc vs Kp
- Replies: 14
- Views: 532
Re: Kc vs Kp
From my understanding:
Kc is for concentrations (mol.L^-1) and Kp is for pressure (bars). The thing is, gases can also be calculated with concentrations so it can use Kc and Kp it just depends what you're given.
If this is incorrect someone please tell me haha.
Kc is for concentrations (mol.L^-1) and Kp is for pressure (bars). The thing is, gases can also be calculated with concentrations so it can use Kc and Kp it just depends what you're given.
If this is incorrect someone please tell me haha.
- Tue Jan 05, 2021 7:20 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Focus 5I.13 (Textbook) Question
- Replies: 1
- Views: 141
Focus 5I.13 (Textbook) Question
Hey guys, So I was trying to solve 5I.13 in the textbook and I understand A and B where you have to solve for X using the ICE box and find out the concentrations of the species. However, I am having a hard time in understanding part C. The part goes as following: " Use your parts from (a) and (...
- Sat Dec 07, 2019 9:47 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
- Replies: 115
- Views: 13110
Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Naren_Ramesh_4D wrote:On question 2b of the mini marshmallow, does the order of the ligand in the coordination complex matter?
I don't think so BUT its good to go in order just in case :)
- Sat Dec 07, 2019 8:49 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
- Replies: 115
- Views: 13110
Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Are we supposed to know how to hybridize lone pairs? Because during class, Lavelle said no but its in marshmallows so im not sure.
- Sat Dec 07, 2019 3:44 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
- Replies: 115
- Views: 13110
Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
ZevMarx-Kahn3C wrote:Hannah Romano 4D wrote:when are the answers for marshmallows being posted???
I'd also love to know!
Fellas, i gotta feeling it's either gonna be really late at night or tomorrow morning. Fluoride ion (F-) in the chemistry community thread.
- Mon Dec 02, 2019 10:25 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: Hydrogen Bond Sites
- Replies: 5
- Views: 390
Re: Hydrogen Bond Sites
Hydrogen bonding occurs when there is a hydrogen bonded to a N,O, or F atom and is attracted to another N,O, or F atom or vise versa. So, the number of hydrogen bonding sites consists of the number or lone pairs on the N,O or F molecules (because they must essentially share electrons with the H ato...
- Mon Dec 02, 2019 10:21 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Chelating complexes
- Replies: 6
- Views: 408
Re: Chelating complexes
If something is a chelate what does that tell us and how would we identify it? Is there more to know other than just the definition of it? I think a good way to see if something is a chelate is to ask yourself "does this central atom have multiple polydentate ligands attached to it?" If t...
- Mon Dec 02, 2019 10:17 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: increasing pH and decreasing pH
- Replies: 4
- Views: 330
Re: increasing pH and decreasing pH
705081525 wrote:More protons means lower pH which means a stronger acid? Correct?
Strong acid= more hydronium ion = low pH
Weak acid= less hydronium ion = high pH
So like, low pH is more acidic and high pH is more basic.
- Mon Dec 02, 2019 10:12 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordination Number
- Replies: 9
- Views: 503
Re: Coordination Number
It's the number of points at which ligands are attached to the central atom. Remember some ligands can connect to the central atom twice (polydentate) so it's not exactly the number of ligands. Do the bi/tri/polydentate is how many times a single ligand can bind to a central transitional metal? Tha...
- Mon Dec 02, 2019 10:11 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Grades
- Replies: 15
- Views: 1064
Re: Grades
Chanel D_4E wrote:Yes, you need at 250 in order to pass with a C-.
Thanks! I totally forgot about this until now.
- Mon Dec 02, 2019 10:10 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: pKa vs Ka
- Replies: 6
- Views: 499
Re: pKa vs Ka
PKa= -Log[Ka] (for weak acids, log of Ka)
Ka= [A-][H+]/[AH] (acid dissociation constant)
Smalled Ka = larger PKa = weaker acid
Ka= [A-][H+]/[AH] (acid dissociation constant)
Smalled Ka = larger PKa = weaker acid
- Tue Nov 26, 2019 9:57 am
- Forum: Administrative Questions and Class Announcements
- Topic: Final Exam Content
- Replies: 14
- Views: 798
Re: Final Exam Content
Yazmin Bocanegra 3L wrote:Is the final exam going to be everything from throughout the quarter, or is it going to be everything from the midterm and beyond?
it's all the material from the quarter
- Tue Nov 26, 2019 9:56 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Use of Bronsted or Lewis Definitions
- Replies: 7
- Views: 396
Re: Use of Bronsted or Lewis Definitions
Trent Yamamoto 4I wrote:In regards to our class, should we use the Bronsted definition or Lewis definition?
Lavelle said any of the two will do :)
- Tue Nov 26, 2019 9:56 am
- Forum: Hybridization
- Topic: How to write
- Replies: 3
- Views: 151
Re: How to write
If you count the number of valence electrons, you can determine the atoms hybridization. For example if you have a Carbon atom, which has 2 electrons in the 2s and 2 electrons in the 2p orbitals, then these orbitals would combine to form a hybridization of sp3. This means that now the Carbon atom c...
- Tue Nov 26, 2019 9:53 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Online Textbook
- Replies: 6
- Views: 381
Re: Online Textbook
Haley Dveirin 4B wrote:Is there a way to access the chemistry textbook online?
If you got the bundle from the UCLA store, you should have received a launchpad code for the online chem book.
- Mon Nov 25, 2019 3:23 pm
- Forum: Air Pollution & Acid Rain
- Topic: Clean Coal vs Dirty Coal?
- Replies: 16
- Views: 1479
Re: Clean Coal vs Dirty Coal?
BeylemZ-4A wrote:can someone explain the difference between clean coal and dirty coal? I remember it being explained in the lecture in terms of Carbon of Sulfur dominant, but I don't remember which was clean and which was dirty.
Clean coal has lower sulfur content but both clean and dirty produce CO2.
- Wed Nov 20, 2019 4:15 pm
- Forum: General Science Questions
- Topic: Final
- Replies: 10
- Views: 716
Re: Final
905174774 wrote:Would the final be cumulative or will we be tested on everything after the midterm?
It's probably cumulative because the midterm was.
- Wed Nov 20, 2019 4:14 pm
- Forum: Electronegativity
- Topic: electronegativity of hydrogen
- Replies: 3
- Views: 343
Re: electronegativity of hydrogen
what is the electronegativity of hydrogen? like if a question asks which has greater ionic character (ie, more EN difference) between HCl and HI or between CH4 and CF4? similarly, where can you imagine hydrogen on the periodic table in terms of where it fits in trends? Hydrogen has low electronegat...
- Wed Nov 20, 2019 4:00 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Ligands
- Replies: 4
- Views: 225
Re: Ligands
Ligands surround the central atom. It's just a name for bonded elements/molecules to central atom.
- Tue Nov 19, 2019 9:25 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Cylindrical Symmetry
- Replies: 1
- Views: 159
Re: Cylindrical Symmetry
I kind of think of it like sigma bonds are gears that help rotate atoms. Kind of like a corndog, you can rotate the corn dog on the stick because the stick allows it to rotate. Weird way to put it, I know, but studying does that to you.
- Tue Nov 19, 2019 9:21 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Can linear molecular shapes have lone pair?
- Replies: 4
- Views: 547
Can linear molecular shapes have lone pair?
It the bond angle is 180*, won't adding a lone pair decrease the 180* and make it non linear? Kind of confused that it says "may have lone pairs" in 2E.1 of homework. Thanks!
- Sun Nov 17, 2019 11:08 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Double and triple bonds
- Replies: 4
- Views: 326
Re: Double and triple bonds
Multiple bonds are still considered one region of electron density.
- Sun Nov 17, 2019 11:07 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: dipole moments
- Replies: 11
- Views: 650
Re: dipole moments
They're kind of like vectors and cancel when they face the opposite direction.
- Sun Nov 17, 2019 11:07 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 7
- Views: 460
Re: Bond Angles
Lone pairs increase bond angles because they repulse electrons more than bonded pairs.
- Sun Nov 17, 2019 11:06 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Naming the Molecular Shapes
- Replies: 7
- Views: 523
Re: Naming the Molecular Shapes
Majority of names are based on geometric shapes but in the case of the few that aren't, you should rely on flashcards with examples of each.
- Sun Nov 17, 2019 11:04 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone vs. Bonding Pair
- Replies: 6
- Views: 383
Re: Lone vs. Bonding Pair
Lone pairs take up more space than bonded pairs.
- Mon Nov 04, 2019 9:30 pm
- Forum: Octet Exceptions
- Topic: Octet Rule exceptions
- Replies: 14
- Views: 871
Re: Octet Rule exceptions
Juliet Stephenson 4E wrote:Hydrogen, Helium, Lithium, and Beryllium are exceptions because they only have s orbitals. Elements that are period 3+ can also potentially expand their octet.
So any element besides the first 10 elements can have expanded octets?