Search found 116 matches
- Sat Mar 13, 2021 8:25 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Thermodynamics Rules/Concepts
- Replies: 3
- Views: 270
Re: Thermodynamics Rules/Concepts
thank you for correcting me!
- Fri Mar 12, 2021 12:12 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Thermodynamics Rules/Concepts
- Replies: 3
- Views: 270
Thermodynamics Rules/Concepts
Hi! I'm sure there are already posts about this but I wanted to ask if you all can list how certain conditions affect the internal energy, entropy, enthalpy, work, etc. So I know that: -if the initial and finals states are the same, dU and dS will be 0 because they are state functions -w=0 in isobar...
- Wed Mar 10, 2021 12:05 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: What was your favorite chem topic?
- Replies: 137
- Views: 7836
Re: What was your favorite chem topic?
from 14A I really liked VSEPR and from 14B I liked thermochemistry. Those were basically the topics I understood the best!
- Mon Mar 08, 2021 12:08 pm
- Forum: Student Social/Study Group
- Topic: Finals
- Replies: 46
- Views: 2836
Re: Finals
I believe the midterms and the finals had relatively similar difficulty levels but the finals were a bit more challenging. It may have been because the finals are cumulative so we need to take into consideration everything we learned during the course, but the UA sessions and OH Dr. Lavelle uploaded...
- Mon Mar 08, 2021 11:56 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: K and Activation Energy
- Replies: 5
- Views: 611
Re: K and Activation Energy
I believe when the activation energy(Ea) increases, the rate constant, k, decreases and when the Ea decreases, k increases. This is because when the Ea is large, it takes the molecules more energy to reach the Ea. This means less molecules will be able to overcome the Ea because not all molecules ha...
- Mon Mar 08, 2021 11:23 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: k'
- Replies: 17
- Views: 764
Re: k'
I was also sort of confused because I thought k' was used to symbolize rate constant in a pseudo rate law. Does this mean the pseudo rate constant is the same as the reverse rate constant?
- Wed Mar 03, 2021 11:35 am
- Forum: First Order Reactions
- Topic: 0.693 ?
- Replies: 39
- Views: 7867
Re: 0.693 ?
Well it should be -0.693 which came from ln(1/2) when we canceled out the initial [A]. Then we rearrange the equation to be t1/2=-0.693/-k and the negatives cancel out giving us
t1/2=0.693/k.
t1/2=0.693/k.
- Wed Mar 03, 2021 11:32 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: galvanic cell textbook problem
- Replies: 1
- Views: 132
Re: galvanic cell textbook problem
I think we reverse the bottom half reaction because we want the Ka for silver chloride so it has to be ka=[Ag+][Cl-]. Therefore, we need the AgCl(s) to be on the reactants side and the Ag+(aq) and Cl-(aq) to be on the products side. So in this case, we aren't looking for a positive standard E cell v...
- Wed Mar 03, 2021 11:26 am
- Forum: Student Social/Study Group
- Topic: Spring Break
- Replies: 53
- Views: 2977
Re: Spring Break
I'm sort of exposing myself but I still don't have my license hahaha. So I hope I get to practice driving!!
- Mon Mar 01, 2021 12:50 pm
- Forum: General Rate Laws
- Topic: Factors Affecting k
- Replies: 83
- Views: 4448
Re: Factors Affecting k
I actually learned this in Chem 20L but k depends on the temperature and catalysts(enzymes). I believe the catalysts lower the activation energy and increase reaction rate.
- Mon Mar 01, 2021 12:42 pm
- Forum: General Rate Laws
- Topic: First order reactions
- Replies: 7
- Views: 412
First order reactions
Can first order reactions have more than one reactant? I am a bit confused because in today's lecture (#22) Dr. Lavelle said the overall reaction order is adding the exponents so if there is more than one reactant, wouldn't it have to be a reaction with an order higher than the first?
- Fri Feb 26, 2021 9:16 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Moles in ΔG = -nFE
- Replies: 45
- Views: 3547
Re: Moles in ΔG = -nFE
I believe it represents the moles of electrons. So we plug in the moles of electrons from the redox reaction we balanced. Hope this helped!
- Thu Feb 25, 2021 4:48 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: When to use Different Nernst Equations
- Replies: 11
- Views: 805
Re: When to use Different Nernst Equations
It looks like they can be used interchangeably because the 0.05916 comes from the constant values. Maybe when we need to use a different R constant to cancel out certain units we would need to use the E = E* - RT/nF(lnQ), but other than that I think either can be used to calculate. To be honest I'm ...
- Thu Feb 25, 2021 4:43 pm
- Forum: Balancing Redox Reactions
- Topic: Week 7/8 Sapling #3
- Replies: 2
- Views: 201
Re: Week 7/8 Sapling #3
Hi!! This wasn't covered in the lecture but Dr. Lavelle sent out an email and told us to check out how to balance acidic/basic redox reactions. Here is the link! https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14B/Balancing_Redox_Reactions_Basic_Conditions.pdf I hope it works and if it...
- Wed Feb 24, 2021 12:12 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Relationship between E naught and spontaneity
- Replies: 8
- Views: 1019
Re: Relationship between E naught and spontaneity
I believe you are correct. When E naught is positive, the redox reaction is spontaneous and if it is negative, it is non-spontaneous (or spontaneous in the reverse reaction). When E naught is 0, it is at equilibrium.
- Wed Feb 24, 2021 12:01 pm
- Forum: Student Social/Study Group
- Topic: Fave food
- Replies: 266
- Views: 25356
Re: Fave food
Sushi is always so good (even though I only eat salmon LOL) and I also love any type of noodle (like ramen, pasta, pho...)
- Mon Feb 22, 2021 12:31 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidizing vs Reducing
- Replies: 55
- Views: 2112
Re: Oxidizing vs Reducing
OIL (oxidation is losing) RIG (reduction is gaining) is what I learned to use in highschool haha. But Dr. Lavelle also have LEO (losing electrons oxidation) and if we know that we lose electrons in oxidation, we know that we gain electrons during reduction. Hope this helped :)
- Mon Feb 22, 2021 11:45 am
- Forum: Ideal Gases
- Topic: Standard temperature
- Replies: 10
- Views: 648
Standard temperature
When we say "standard temperature," are we referring to the STP (273K) or SATP (298K)?
- Fri Feb 19, 2021 9:33 pm
- Forum: Student Social/Study Group
- Topic: Post Midterm 2 De-stressing
- Replies: 92
- Views: 5749
Re: Post Midterm 2 De-stressing
My favorite way to de-stress is to binge watch all the shows I couldn't watch because I had to study haha. I also like to de-stress through retail therapy and I know it's a bad habit but I like to reward myself with something (even if it's something small) to keep me going. Also I just love waiting ...
- Thu Feb 18, 2021 6:55 pm
- Forum: Student Social/Study Group
- Topic: Delta U=0
- Replies: 6
- Views: 432
Re: Delta U=0
I believe delta U=0 when a reaction is isothermal, whether it be reversible or irreversible.
- Wed Feb 17, 2021 12:21 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: anode and cathode L/R
- Replies: 14
- Views: 579
anode and cathode L/R
I remember in highschool, my chem teacher told me that the anode is not always on the left and the cathode is not always on the right but in today's lecture, 17, Dr. Lavelle had the anode as left and cathode as right(in lec notes). Does that mean we'll always be given diagrams with anodes on the lef...
- Mon Feb 15, 2021 4:24 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: confusion on using Cp and Cv
- Replies: 24
- Views: 965
Re: confusion on using Cp and Cv
What I like to do is I use the one that is mentioned in the problem. If the question is focusing on volume I use Cp and when it is focusing on pressure I use Cp. Although we may be given the initial and final volumes/pressures in the question, when we calculate using the Cv of Cp, we assume the volu...
- Mon Feb 15, 2021 4:18 pm
- Forum: Student Social/Study Group
- Topic: Studying for Midterm 2
- Replies: 45
- Views: 1674
Re: Studying for Midterm 2
To be honest I just go to as many workshops as I can so I can get more practice and it helps me understand the topics better when I hear someone explain the concepts over and over again. I also do the wkbk problems and go over homework problems that were challenging.
- Fri Feb 12, 2021 2:50 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Standard Gibbs Free Energy
- Replies: 8
- Views: 453
Re: Standard Gibbs Free Energy
If K is a large value, ln(K) will be a positive value. Since there is a negative in the front, -RT(+number) will be negative. If K was a value less than 1, the lnK value will be a negative number giving us -RT(-number) making it positive. Delta G (standard) can only be 0 when K=1 (because ln(1)=0) a...
- Fri Feb 12, 2021 2:41 pm
- Forum: Calculating Work of Expansion
- Topic: Sign of work
- Replies: 25
- Views: 816
Re: Sign of work
I don't know if I am answering your question correctly but when work is done ON the system, the system is gaining energy so it'll be positive and when the work is done BY system, it will be using up energy so work will be negative. Maybe that is why the signs are switched. Hope this helps!
- Wed Feb 10, 2021 3:37 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Sapling #6
- Replies: 2
- Views: 149
Re: Sapling #6
like what the above comment says, we need to use both the deltaS=nRln(V2/V1) for volume change and deltaS=nCln(T2/T1) for the temperature change. One you found the two values you just add them up!
- Wed Feb 10, 2021 3:13 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Sapling wk 5/6 #3
- Replies: 2
- Views: 130
Sapling wk 5/6 #3
Classify the phase changes by the signs of the system's ΔH and ΔS. So I know that when entropy is negative, it is becoming more ordered and when it is positive, it becomes more disordered. However, How would something that is going from a solid to liquid, liquid to gas, solid to gas, have a negative...
- Mon Feb 08, 2021 12:18 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: work and pos/neg
- Replies: 9
- Views: 460
Re: work and pos/neg
When the system is doing the work, the work is being done to the surroundings. Therefore, the surroundings gain the work and system loses work and w would be negative. On the other hand, if the system was gaining the work and the surrounding was doing the work on the system, w would be positive beca...
- Mon Feb 08, 2021 12:15 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Entropy in an Isolated System
- Replies: 4
- Views: 211
Re: Entropy in an Isolated System
I'm not sure if I'm 100% correct but I would assume the entropy would not change if the system is isolated. This is because there would technically be no change in the surroundings.
Maybe there are other instances that do change the entropy?
Maybe there are other instances that do change the entropy?
- Fri Feb 05, 2021 5:44 pm
- Forum: Calculating Work of Expansion
- Topic: sapling wk 4 #14
- Replies: 6
- Views: 240
sapling wk 4 #14
A sample of an ideal gas in a cylinder of volume 4.28 L at 298 K and 2.52 atm expands to 7.35 L by two different pathways. Path A is an isothermal, reversible expansion. Path B has two steps. In the first step, the gas is cooled at constant volume to 1.49 atm . In the second step, the gas is heated ...
- Wed Feb 03, 2021 12:48 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: Microstates vs. Possible positions
- Replies: 3
- Views: 93
Microstates vs. Possible positions
I'm kind of confused because in another post people are saying "X", in the W=X^n equation, is the number of microstates, but I thought X was the amount of possible positions(left and right) and microstates were the amount of arrangements the particles could be arranged within the possible ...
- Wed Feb 03, 2021 12:20 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: Microstates
- Replies: 16
- Views: 970
Re: Microstates
In Lavelle's lecture from today (2/3), he talks about a 2 particle system with 4 microstates and says the degeneracy would be W=4=2^2. I'm a little confused by this, because in the discussion above, it says that W=X^n, where X is the number of microstates and n is the number of particles. So, would...
- Mon Feb 01, 2021 11:51 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Change in internal energy: q vs qv
- Replies: 4
- Views: 159
Re: Change in internal energy: q vs qv
I believe qv is just heat at a constant volume because Dr. Lavelle also used qp as heat at a constant pressure.
- Mon Feb 01, 2021 11:32 am
- Forum: Calculating Work of Expansion
- Topic: What is V1 and V2
- Replies: 12
- Views: 617
Re: What is V1 and V2
V1 would be the initial volume and the V2 would be the final volume. In the integral, it goes from V1 to V2 so it would be the sum of all the work done from initial to final.
- Fri Jan 29, 2021 9:06 pm
- Forum: Calculating Work of Expansion
- Topic: week 3/4 hw #13
- Replies: 2
- Views: 132
Re: week 3/4 hw #13
The solution for the problem says that a system that works on the surrounding should have a negative value for work(w). Hope this helps!
- Wed Jan 27, 2021 2:56 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 4D 17 Calculation Error
- Replies: 2
- Views: 128
Re: 4D 17 Calculation Error
This is what I did. Since there are 4 HNO3(l) it will be 4(-174.10) and there are 5N2H4(l) it will be 5(50.63). There are 12H2O(l) so it will be 12(-258.83). Then I added up all the reactants together. After, I subtracted the reactants from the products [products-reactants] and I got -2986.71 KJ. It...
- Wed Jan 27, 2021 12:23 pm
- Forum: Ideal Gases
- Topic: Exo vs Endothermic
- Replies: 40
- Views: 2175
Re: Exo vs Endothermic
I'm not too sure but I think this reaction would be exothermic because it's the synthesis of CO2 gas. Synthesis reactions are exothermic because they release heat to be produced. Also when bonds are being formed, it is an exothermic reaction and when the bonds are being broken the reaction would be ...
- Mon Jan 25, 2021 1:21 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: QSys + QSurr
- Replies: 4
- Views: 187
Re: QSys + QSurr
Pranav Kadiyala 1A wrote:In Lecture #9 Dr. Lavelle uses the Qsys + Qsurr equation to determine the sign of the qp value. How would that same calculation look for an exergonic rxn?
What is the difference between an exothermic and an exergonic reaction? Wasn't the example shown in the lecture an exothermic reaction?
- Mon Jan 25, 2021 12:59 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Ice melting
- Replies: 5
- Views: 299
Ice melting
In lecture #9, Dr. Lavelle was going through an example and said it was an exothermic reaction because the heat was increased. I thought the reaction would be endothermic because when we look at the ice melting situation, we need more heat to melt the ice which is increasing the temperature. Can som...
- Fri Jan 22, 2021 12:04 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm for students with Friday Discussions
- Replies: 3
- Views: 150
Re: Midterm for students with Friday Discussions
I asked my TA and he said we still do have discussion. It'll just be like a review or the midterm but we still have it on friday!
- Thu Jan 21, 2021 4:46 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm for students with Friday Discussions
- Replies: 3
- Views: 150
Re: Midterm for students with Friday Discussions
I didn't hear anything about discussion being cancelled Friday for midterms. I'm assuming we still have them because it doesn't interfere with the midterm times? Maybe they'll use it to go over material before midterms. I'm in 3I which is at 12 Friday. I'll ask this week :)
- Wed Jan 20, 2021 12:04 pm
- Forum: Phase Changes & Related Calculations
- Topic: Adding Heat but Temp remains constant
- Replies: 11
- Views: 354
Re: Adding Heat but Temp remains constant
I also had this question because if heat is being used to break the bonds, I assumed it would also have to be released. However, maybe it's just being used as energy? Or maybe it's like the graph where the line stays constant when the phases are being changed.
- Wed Jan 20, 2021 11:48 am
- Forum: Phase Changes & Related Calculations
- Topic: 1/20/21 Lecture- What is bulk property?
- Replies: 3
- Views: 365
Re: 1/20/21 Lecture- What is bulk property?
I just searched it up and it says that a bulk property is a physical property that does not depend on the size or mass of a sample, which is considered an intensive property.
- Mon Jan 18, 2021 5:17 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Textbook Question Kw
- Replies: 5
- Views: 179
Re: Textbook Question Kw
I was also confused as to how we were supposed to know [H3O+]=[OH-]. I just assumed it was because [H3O+][OH-]=Kw and nothing else is specified except the temperature.
- Fri Jan 15, 2021 5:08 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Strong Acid and Base
- Replies: 4
- Views: 226
Strong Acid and Base
Hi, I was having a hard time trying to understand solving for pH/pOH of strong acids and bases. So, I understand that when there is a strong acid or base, it will completely dissociate, so we will have to write a new equation or make a second ICE table but I do not understand why the dissociation ma...
- Thu Jan 14, 2021 11:01 am
- Forum: Student Social/Study Group
- Topic: Comfort Movies
- Replies: 168
- Views: 21737
Re: Comfort Movies
This might sound stupid but I used to watch a lot of barbie movies when I was young so they've become my comfort movies and I watch them once in a while ahahah
- Thu Jan 14, 2021 10:23 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: net ionic equations
- Replies: 4
- Views: 152
net ionic equations
In what situations are we supposed to be using net ionic equations and would we be told to use it or do we just have to know?
Also, when we use net ionic equations, do we dissociate only the aqueous solutions and leave the liquids and solids be?
Also, when we use net ionic equations, do we dissociate only the aqueous solutions and leave the liquids and solids be?
- Wed Jan 13, 2021 9:30 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Several Questions
- Replies: 3
- Views: 124
Several Questions
1. I was doing a problem from one of the UA worksheets and it said to find the [OH-] and [H+]. I was confused at first but H+ and H3O+ mean the same right?
2. When we have a reaction, we neglect water but only when it is in the liquid form right?
Thank you for your help!
2. When we have a reaction, we neglect water but only when it is in the liquid form right?
Thank you for your help!
- Mon Jan 11, 2021 1:04 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Cubic Equations
- Replies: 6
- Views: 238
Cubic Equations
So just to make sure, we only omit x when the Kc is smaller than 1.0x10^-3 right? (of course only omit the x's being subtracted and I would assume the ones being added also, but not the ones being multiplied). Also, does Kc need to be significantly less than 1.0x10^-3 or just less than 1.0x10^-3? Th...
- Fri Jan 08, 2021 11:21 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Hw #9
- Replies: 2
- Views: 3308
Re: Sapling Hw #9
At equilibrium, the concentrations in this system were found to be [N2]=[O2]=0.100 M and [NO]=0.600 M. N2(g)+O2(g)↽−−⇀2NO(g) If more NO is added, bringing its concentration to 0.900 M, what will the final concentration of NO be after equilibrium is re‑established? Hi. I know there's already a post ...
- Fri Jan 08, 2021 9:37 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Hw #9
- Replies: 2
- Views: 3308
Sapling Hw #9
At equilibrium, the concentrations in this system were found to be [N2]=[O2]=0.100 M and [NO]=0.600 M. N2(g)+O2(g)↽−−⇀2NO(g) If more NO is added, bringing its concentration to 0.900 M, what will the final concentration of NO be after equilibrium is re‑established? Hi. I know there's already a post a...
- Fri Jan 08, 2021 11:23 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium Constant values.
- Replies: 3
- Views: 322
Re: Equilibrium Constant values.
I believe it's because when we look at how the equation is set up, the equilibrium constant value= [products]/[reactants]. Therefore, if the K value is large, we can conclude that there are more products(larger number divided by smaller number= large number) and if the K value is small, we can concl...
- Thu Jan 07, 2021 4:49 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Partial pressure vs concentration
- Replies: 6
- Views: 324
Re: Partial pressure vs concentration
I think you can use Kc and Kp for gases. It would just depend on what the questions is asking you. If the given is in molar concentrations you would use Kc and if it were given in partial pressure units you would use Kp. Hope this helped!
- Wed Jan 06, 2021 11:40 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Table 5G.2 Equilibrium Constants chart
- Replies: 1
- Views: 120
Table 5G.2 Equilibrium Constants chart
I was doing the workbook problems and came across this the Equilibrium Constants for Various Reactions chart. Some of the problems required us to use this chart but I did not know which values (K or Kc) to use and how to use the them if there were equations that were combined. Can someone please exp...
- Tue Jan 05, 2021 1:56 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Question #4 sapling ICE box
- Replies: 2
- Views: 86
Question #4 sapling ICE box
Sapling problem #4 gave us the equilibrium equation PCl3(g)+Cl2(g)=PCl5(g) and said the PCl5 was placed in the container so I understand that we would input the initial value for PCl5 and put 0 for PCl3 and Cl2, but why don't we put the equation as a reverse reaction instead of keeping the equation ...
- Tue Jan 05, 2021 1:51 pm
- Forum: Student Social/Study Group
- Topic: Advice for someone who didn't take 14A with professor Lavelle
- Replies: 61
- Views: 2602
Re: Advice for someone who didn't take 14A with professor Lavelle
One thing I regret not doing last quarter is not going to the workshops and step up sessions until finals week. They helped a lot, but I know if I went from the beginning of the quarter I would've gotten better results so I would go to workshops if you do not understand or are having trouble underst...
- Fri Dec 11, 2020 11:16 am
- Forum: Biological Examples
- Topic: question about cisplatin
- Replies: 2
- Views: 174
Re: question about cisplatin
So I searched it up and it says the chlorines leave to create a reactive space for the guanine to attach.
- Wed Dec 09, 2020 11:04 am
- Forum: Identifying Acidic & Basic Salts
- Topic: Salt Acidic Ions
- Replies: 3
- Views: 191
Re: Salt Acidic Ions
I believe Dr. Lavelle said that the NH4+ ion is what makes the solution more acidic as it has a proton that it can donate. The compound that was formed was the NH4Cl with the reactants HCl and NH3.
- Wed Dec 09, 2020 10:55 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Determining Shape
- Replies: 10
- Views: 605
Re: Determining Shape
The molecular shape describes the regions/arrangements of bonds and bonds only while the electron geometry describes the regions/arrangements of bonds as well as lone pairs. For example, if the VSEPR name is AX3E1, the molecular geometry would be trigonal pyramidal while the electron geometry would ...
- Mon Dec 07, 2020 11:29 am
- Forum: Bronsted Acids & Bases
- Topic: When to use Bronsted and Lewis
- Replies: 2
- Views: 74
When to use Bronsted and Lewis
I understand that Bronsted acids and bases focus on the movement on protons while Lewis acids and bases focus on the movement of electrons. But when people mention that a species is an acid or base do they usually refer to the Bronsted or the Lewis form? Does this also mean we have to look at what t...
- Mon Dec 07, 2020 11:19 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Group 1,2, and Metalloids don't affect acidity?
- Replies: 2
- Views: 139
Re: Group 1,2, and Metalloids don't affect acidity?
I believe Dr. Lavelle said the interaction won't be strong enough to break the bond and therefore they won't be able to change the structure of the water molecule! Hope this helps.
- Mon Dec 07, 2020 10:49 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: practice problem 1D 19
- Replies: 2
- Views: 160
Re: practice problem 1D 19
Yes those are the answers!
s has 1 orbital
p has 3 orbitals
d has 5 orbitals
f has 7 orbits
as each orbital can hold 2 electrons
s has 1 orbital
p has 3 orbitals
d has 5 orbitals
f has 7 orbits
as each orbital can hold 2 electrons
- Fri Dec 04, 2020 4:41 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: exchanging H for Cl allows for resonance
- Replies: 2
- Views: 177
Re: exchanging H for Cl allows for resonance
I believe it becomes more acidic because the Cl is withdrawing the electrons from the oxygen. Like the example with Cl-O-H, the Cl is the most electronegative out of Cl, Br, and I, therefore stabilizing the O by withdrawing the electron density. This makes it more acidic. Hope this helps!
- Thu Dec 03, 2020 12:56 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Isomers
- Replies: 2
- Views: 107
Isomers
Hi. I was just in my discussion group and we discussed about isomers but don't remember learning about them in the lectures. Will isomers be on the final exam or is it just something we should hold onto for 14B? Thank you!
- Thu Dec 03, 2020 12:10 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Textbook question 2E. 1
- Replies: 3
- Views: 179
Re: Textbook question 2E. 1
There may be an even number of lone pairs that cancel out their repulsions which is why the bond angle wouldn't change. Hope this helped!
- Wed Dec 02, 2020 1:09 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Vinegar on a cut
- Replies: 4
- Views: 179
Vinegar on a cut
In the beginning of Dr. Lavelle's lecture 26, he talks about having a cut on our finger and touching vinegar. The vinegar stings and we wash it off immediately because it damages/ denatures the proteins. Does this mean that it is bad to not wash my hands immediately after I eat vinegar chips(or any ...
- Wed Dec 02, 2020 1:02 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chem 14A Final
- Replies: 21
- Views: 1023
Re: Chem 14A Final
I don't really know if the questions will be an even distribution of all the topics but I do know that the final will be cumulative. So it will have all the topics we cover in the class. Hope this helped!
- Tue Dec 01, 2020 4:56 pm
- Forum: Lewis Structures
- Topic: Octet rule
- Replies: 12
- Views: 580
Re: Octet rule
Thank you to the people that replied! I will be checking the textbook pages for more info!
- Sun Nov 29, 2020 5:52 pm
- Forum: Lewis Structures
- Topic: Octet rule
- Replies: 12
- Views: 580
Octet rule
Hi! So I was doing the sapling workbook problems and realized that for 2E.19, most of the central atoms in this problem did not fulfill the octet rule. Are Be, B, and Sn exceptions to the octet rule or does it only work in this case? Thank you for any help!
- Thu Nov 26, 2020 12:16 am
- Forum: Sigma & Pi Bonds
- Topic: Sapling hw #16
- Replies: 2
- Views: 198
Re: Sapling hw #16
I believe in the 23rd lecture, Dr. Lavelle used benzene (C6H6) as a molecule with delocalized pi bonds. This is because of their resonance structures and because the 6 electrons are shared equally. Therefore, when electron the electron density is shared equally, the pi bonds are considered delocaliz...
- Tue Nov 24, 2020 7:13 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Grade Adjustment after Final
- Replies: 2
- Views: 143
Re: Grade Adjustment after Final
The shift usually depends on how well the class as a whole does. So the shift would have to depend on the class average!
- Tue Nov 24, 2020 7:10 pm
- Forum: Hybridization
- Topic: d hybridized orbital confusion
- Replies: 7
- Views: 323
Re: d hybridized orbital confusion
On Monday's lecture, Dr. Lavelle said you could write it either way. Both dsp^3 and sp^3d are correct :)
- Tue Nov 24, 2020 7:07 pm
- Forum: Student Social/Study Group
- Topic: Big Sad: Midterm 2
- Replies: 86
- Views: 5343
Re: Big Sad: Midterm 2
I also felt the same way because I believe I'm better at solving rather than answering conceptual problems. I was also a bit worried that there were no partial points this time because nothing really involved solving. However, I don't think you need to worry too much as a 250/500(50%) is a passing g...
- Tue Nov 24, 2020 7:01 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Class Grading Scale
- Replies: 7
- Views: 361
Re: Class Grading Scale
From reading the comments from the other post about curves, I believe that depends on the class average. One person said they got a final grade of 344/500 and got a C for the class. It is said that once the class average is determined, grades will shift accordingly. I don't fully know the details th...
- Mon Nov 23, 2020 11:21 am
- Forum: Hybridization
- Topic: Energy Gap
- Replies: 5
- Views: 257
Re: Energy Gap
Thank you so much for your replies! This helped so much!
- Mon Nov 23, 2020 11:10 am
- Forum: Hybridization
- Topic: Energy Gap
- Replies: 5
- Views: 257
Energy Gap
In today's lecture (11/23) Dr. Lavelle talked about how since the energy gap for 2p and 2sp3 is smaller than 2p and 2s, the electrons for 2p and 2sp3 are unpaired. How do we know that the energy gap is smaller or larger? Thank you!
- Fri Nov 20, 2020 1:02 pm
- Forum: Hybridization
- Topic: Hybridization
- Replies: 7
- Views: 166
Hybridization
Hi. So I'm a little confused about the concept of hybridization. I understand that we're combining the 2s^2 and the 2p^2(in the example from the lecture), but why does only one electron from the s orbital go to the p orbital? Or am I not understanding it? Sorry I was kinda out of it today and couldn...
- Wed Nov 18, 2020 11:38 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular geometry vs. shape
- Replies: 4
- Views: 269
Molecular geometry vs. shape
Hi. So just to clarify, the geometry of a molecule is different from the actual shape of it right? Because in the lecture, SF4 had a geometry of trigonal bipyramidal but a shape of a seesaw. Same goes for XeF4, which had a geometry of octahedral but a shape of a square planar. Thank you for any help!
- Tue Nov 17, 2020 1:14 pm
- Forum: Resonance Structures
- Topic: 2C #3a Iodine Expanded Octet
- Replies: 2
- Views: 140
Re: 2C #3a Iodine Expanded Octet
Hi! I found this on chem community!
viewtopic.php?t=8510#:~:text=Re%3A%20Having%20more%20than%208%20valence%20electrons&text=Some%20molecules%20can%20accommodate%20more,more%20that%209%20valence%20electrons.
Hope this helps!
viewtopic.php?t=8510#:~:text=Re%3A%20Having%20more%20than%208%20valence%20electrons&text=Some%20molecules%20can%20accommodate%20more,more%20that%209%20valence%20electrons.
Hope this helps!
- Tue Nov 17, 2020 1:08 pm
- Forum: Electronegativity
- Topic: Textbook Problem 2D.3
- Replies: 5
- Views: 131
Re: Textbook Problem 2D.3
I'm sorry, but I still do not quite understand how we measure the difference in electronegativity. Do we have to count the amount of elements in between them? or do we compare the sizes of the elements? Thank youu for any help! Oh. I just realized I could just look at the electronegativity chart......
- Tue Nov 17, 2020 1:05 pm
- Forum: Electronegativity
- Topic: Textbook Problem 2D.3
- Replies: 5
- Views: 131
Re: Textbook Problem 2D.3
I'm sorry, but I still do not quite understand how we measure the difference in electronegativity. Do we have to count the amount of elements in between them? or do we compare the sizes of the elements? Thank youu for any help!
- Mon Nov 16, 2020 10:09 pm
- Forum: Electronegativity
- Topic: Textbook Problem 2D.3
- Replies: 5
- Views: 131
Textbook Problem 2D.3
I honestly do not know if this fits into this topic but I needed help with Which of these compounds has bonds that are primarily ionic? (a) BBr3; (b) BaBr2; (c) BeBr2. I thought we were just supposed to see how far away the two elements were to see the largest difference in electronegativity, but I ...
- Mon Nov 16, 2020 10:33 am
- Forum: Lewis Structures
- Topic: "Plausible" Lewis Structures
- Replies: 7
- Views: 1040
Re: "Plausible" Lewis Structures
A "plausible" lewis structure is a structure with formal charges of 0 on all atoms! Hope this helpss.
- Fri Nov 13, 2020 8:01 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Oxidation Number
- Replies: 8
- Views: 369
Re: Oxidation Number
When I took chemistry in high school, I had to memorize the oxidation numbers. Group1 is +1, Group2 is +2, Fluorine is -1, Group15 is -1, Group16 is -2, Group17 is -3, Oxygen is usually -2(not when with fluorine or peroxides), Hydrogen is +1 when paired with non-metals and -1 when paired with metals...
- Fri Nov 13, 2020 10:21 am
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizable vs. Polarizability
- Replies: 5
- Views: 437
Polarizable vs. Polarizability
Hi. So to my understanding, if something is polarizable, it is getting polarized and the bigger the radius, the more polarizable(easier to distort). When talking about polarizability, are we talking about what can do the most polarizing? So the more electronegative and smaller the radius, the more p...
- Wed Nov 11, 2020 1:16 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Sapling week 5/6 #5
- Replies: 6
- Views: 405
Re: Sapling week 5/6 #5
Hi! Carbon should have a formal charge of 2- not 1- Hope this helps.
- Mon Nov 09, 2020 12:08 pm
- Forum: Ionic & Covalent Bonds
- Topic: Hydrogen Bonds [ENDORSED]
- Replies: 9
- Views: 480
Hydrogen Bonds [ENDORSED]
I remember learned that hydrogen bonds were dipole dipole. Does this mean that hydrogen bonds are just stronger types of dipole dipole bonds? Thanks for your help!
- Mon Nov 09, 2020 12:03 pm
- Forum: Ionic & Covalent Bonds
- Topic: negative energies for attractive interactions
- Replies: 7
- Views: 248
Re: negative energies for attractive interactions
I believe the energies are negative because they are being released. I'm not completely sure but I remember Dr. lavelle saying that in the lecture. Hope this helped!
- Thu Nov 05, 2020 10:20 pm
- Forum: Lewis Structures
- Topic: Radicals
- Replies: 9
- Views: 340
Re: Radicals
Radicals are compounds that have electrons with unpaired spins, and it is an exception to the octet guideline. Because of this unpaired electron, the compound becomes highly reactive and unstable. When you draw the lewis structure, and there is an odd number of electrons, one of the electrons will ...
- Wed Nov 04, 2020 9:24 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Textbook Problem 1E.5
- Replies: 2
- Views: 82
Textbook Problem 1E.5
Which of the following statements are true for many-electron atoms? If false, explain why. (a) The effective nuclear charge Zeffe is independent of the number of electrons present in an atom. (b) Electrons in an s-orbital are more effective than those in other orbitals at shielding other electrons f...
- Wed Nov 04, 2020 11:17 am
- Forum: Octet Exceptions
- Topic: Radicals
- Replies: 5
- Views: 164
Re: Radicals
Free radicals are formed from molecules via the breakage of a chemical bond such that each fragment keeps one electron, also via redox reactions in the body. I'm not sure what specifically would happen if you were vitamin deficient, but oxidative stress can arise when cells cannot adequately destro...
- Wed Nov 04, 2020 11:01 am
- Forum: Ionic & Covalent Bonds
- Topic: SO4 covalent bond
- Replies: 6
- Views: 158
Re: SO4 covalent bond
I believe he was showing us a different way to draw the lewis structure of SO42- to show us how to make the formal charge of S equal 0. This would mean the structure with the FC of S=0 is more stable than the other structure where the FC of S=2+. Hope this helps!
- Tue Nov 03, 2020 8:02 pm
- Forum: Lewis Structures
- Topic: Lewis Structure
- Replies: 7
- Views: 161
Lewis Structure
Hii. So I was just a little confused about which elements should go in the middle when drawing the Lewis Structures. I would always put the element with multiple on the outsides and the one element on the inside, but it's not really helpful when there are more than two different elements.
- Sun Nov 01, 2020 2:57 pm
- Forum: Ionic & Covalent Bonds
- Topic: Van Der Waals radius
- Replies: 4
- Views: 106
Re: Van Der Waals radius
Referring to general atomic radius, why does gaining an electron make the radius bigger and losing an electron make the radius smaller? I go this off of the internet but it's because when gaining an electron, more electrons are added to the outermost shell so the electrons are further away from the...
- Sun Nov 01, 2020 2:50 pm
- Forum: Student Social/Study Group
- Topic: Favorite TV shows
- Replies: 277
- Views: 33381
Re: Favorite TV shows
Hii. I enjoyed watching The Good Place and The Umbrella Academy on Netflix! My back up show is Gilmore Girls. Lol. I usually just watch it when I have nothing else to watch.
- Sun Nov 01, 2020 2:48 pm
- Forum: Student Social/Study Group
- Topic: How to relax
- Replies: 168
- Views: 20321
Re: How to relax
Hii. Well, I usually like to watch netflix or youtube, but I also love listening to music while doodling :)
- Sun Nov 01, 2020 2:47 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm grades
- Replies: 19
- Views: 745
Re: Midterm grades
Hii. I'm not sure exactly when but Dr. Lavelle will probably send an email out if the grades are out! Hope this helped.
- Sat Oct 31, 2020 3:59 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: n and l numbers
- Replies: 5
- Views: 329
Re: n and l numbers
Hii. So l represents the shape of an orbital or specific subshell. l=0 is s, l=1 is p, l=2 is d, and l=3 is f.
- Sat Oct 31, 2020 8:55 am
- Forum: Properties of Light
- Topic: Electromagnetic Spectrum
- Replies: 7
- Views: 400
Re: Electromagnetic Spectrum
All of these methods are so helpful! Thank you all so much for the ideas. I will definitely use them to memorize!
- Fri Oct 30, 2020 10:44 pm
- Forum: Properties of Light
- Topic: Electromagnetic Spectrum
- Replies: 7
- Views: 400
Electromagnetic Spectrum
Hi. I know we already had our midterms, but I wanted to know an easy way to memorize the electromagnetic spectrum. Not just the order of the radiation type but also the wavelengths that corresponds with the radiation types. Thank you!