Search found 99 matches

by Sara_Lim_2C
Sun Mar 07, 2021 10:52 pm
Forum: Student Social/Study Group
Topic: Classes for next quarter?
Replies: 145
Views: 472

Re: Classes for next quarter?

Chem 14BL, LS7A, and Arch & Urban Design 10B!
by Sara_Lim_2C
Sun Mar 07, 2021 10:45 pm
Forum: Balancing Redox Reactions
Topic: Balancing redox reactions
Replies: 5
Views: 9

Re: Balancing redox reactions

I believe you can add OH- on both sides as needed to cancel out any remaining H+ and make them H2O. Since it's in a basic solution you just don't want any H+ left in the final equation. But you can have leftover OH-. Hope that helps!
by Sara_Lim_2C
Sun Mar 07, 2021 10:33 pm
Forum: General Rate Laws
Topic: The value, 0.693
Replies: 4
Views: 19

Re: The value, 0.693

It's from the 1st order half life equation, t1/2=0.693/k; The derivation is in Lecture 23 if you're curious :D
by Sara_Lim_2C
Sun Mar 07, 2021 10:10 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Chemical Reactions and Temperature
Replies: 3
Views: 8

Re: Chemical Reactions and Temperature

I believe an increase in temperature causes the molecules in the reaction to move faster, and thus collide with each other more. More collisions means a high possibility of a reaction occurring, so that increases the rate of reaction. Hope that answers your question!
by Sara_Lim_2C
Sun Mar 07, 2021 10:08 pm
Forum: General Rate Laws
Topic: General Rate Law vs Half life
Replies: 4
Views: 13

Re: General Rate Law vs Half life

The general rate law will be used for anything like finding final or initial concentration, time taken for a reaction to occur, or the rate constant, depending on what information you're given. The half life (from my knowledge) will only be used if a question explicitly asks you for the half life of...
by Sara_Lim_2C
Sun Mar 07, 2021 8:48 pm
Forum: Student Social/Study Group
Topic: Almost through!
Replies: 6
Views: 22

Re: Almost through!

I'm proud that my midterm scores in this class were better than last quarter! I had a lot of trouble on those midterms in 14A and I'm glad it was a little better this time!
by Sara_Lim_2C
Sun Feb 28, 2021 11:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Sapling #17
Replies: 10
Views: 86

Re: Sapling #17

How did you get that Q is pressure divided by [H+]? I'm not sure how that gives Q. I think we treat the pressure of H2 as partial pressure or concentration since it's a gas, so we can plug this into the expression for Q and solve for it Ohhhh ok that makes sense. Thanks! I was having quite a bit of...
by Sara_Lim_2C
Sun Feb 28, 2021 11:37 pm
Forum: Student Social/Study Group
Topic: Playlist
Replies: 57
Views: 172

Re: Playlist

One of my favorite songs at the moment is Hailey by WRENN! I'm also really into the New Hope Club's recent album, particularly their songs How to Say I Love You and We Broke Up In A Dream. All three are some good break up bops :D
by Sara_Lim_2C
Sun Feb 28, 2021 11:33 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Sapling #17 / E naught = 0?
Replies: 3
Views: 17

Re: Sapling #17 / E naught = 0?

We know E naught is zero from the standard reduction potential chart. The other potential, E, what the question is asking for, is E when the reaction is not at standard conditions. I believe that since the concentration is not at 1.0 M, it is not at standard conditions. So we use the E naught and th...
by Sara_Lim_2C
Sun Feb 28, 2021 9:10 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Sapling Week 7/8 question 15
Replies: 6
Views: 22

Re: Sapling Week 7/8 question 15

I solved this by using this version of the Nernst Equation: E= (E naught) - (0.05916V/n)log(Q). Use the standard reductions table to find E naught of the half reactions, and use those to find the E naught the whole reaction. Then use the two concentrations to find Q, which is [Cr 2+ ]/[Fe 2+ ]. n is...
by Sara_Lim_2C
Sun Feb 28, 2021 8:37 pm
Forum: General Science Questions
Topic: Midterm 2 Reactions
Replies: 79
Views: 243

Re: Midterm 2 Reactions

I was pleasantly surprised! Last quarter, Midterm 2 absolutely tanked my grade, so I'm glad that didn't happen again!
by Sara_Lim_2C
Sun Feb 28, 2021 8:02 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Sapling #15
Replies: 3
Views: 24

Re: Sapling #15

I think E naught should be 0.47V. Your two half reactions should be Cr->Cr 2+ +2e - , which is 0.91V (if you reverse the original reduction potential) and Fe 2+ +2e - ->Fe, which is -0.44V. When you add those together, that's 0.47V. I may be wrong, but I think that may be it? Could someone else veri...
by Sara_Lim_2C
Sun Feb 28, 2021 7:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Sapling #17
Replies: 10
Views: 86

Re: Sapling #17

How did you get that Q is pressure divided by [H+]? I'm not sure how that gives Q.
by Sara_Lim_2C
Fri Feb 26, 2021 9:48 am
Forum: Balancing Redox Reactions
Topic: Acidic vs. Basic
Replies: 20
Views: 36

Re: Acidic vs. Basic

If balancing in a basic solution, you theoretically don't want H+ ions in the equation. So to cancel those out, add OH- to each side of the reaction. I assume the opposite is true for acidic ones. Hope that helps!
by Sara_Lim_2C
Tue Feb 23, 2021 11:37 am
Forum: Student Social/Study Group
Topic: How to Reduce Nervousness before getting results
Replies: 37
Views: 104

Re: How to Reduce Nervousness before getting results

I'm the same way! Sometimes my friends will say that there's nothing I can do about it anymore, which helps a little, but it usually doesn't take away the feeling that I could've done better. I still feel guilty about my past self, as if I didn't try hard or study enough. So for me, I just put on so...
by Sara_Lim_2C
Tue Feb 23, 2021 11:34 am
Forum: Student Social/Study Group
Topic: Fave food
Replies: 163
Views: 342

Re: Fave food

My favorite meal is definitely pasta of any kind, but my favorite snack is probably Goldfish. Also funny you mentioned banana bread because my mom just made some the other day!
by Sara_Lim_2C
Sun Feb 14, 2021 10:25 pm
Forum: General Science Questions
Topic: Baking/Cooking Chemistry
Replies: 1
Views: 22

Baking/Cooking Chemistry

I was confused about something that happened while baking, and was wondering if there was a potential chemistry related answer? Here goes: My brother was making browned butter for some cookies (basically just butter that's cooked over the stove before you put it in your dough). So he heated up the b...
by Sara_Lim_2C
Sun Feb 14, 2021 10:17 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneity of a System
Replies: 37
Views: 88

Re: Spontaneity of a System

I have a similar problem with remembering which signs are spontaneous at different temperatures, and I definitely recommend looking up a spontaneity chart! Looking at one of those helps me remember the relationships between the different values in formulas.
by Sara_Lim_2C
Sun Feb 14, 2021 10:11 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sapling Weeks 5-6 #3
Replies: 4
Views: 20

Re: Sapling Weeks 5-6 #3

Yep! It's kind of a trick question; for all of them, they either fall in delta H and delta S both positive or both negative.
by Sara_Lim_2C
Sun Feb 14, 2021 10:01 pm
Forum: Student Social/Study Group
Topic: Spring 2021
Replies: 104
Views: 448

Re: Spring 2021

I'm planning on taking BL because I don't want to start a new series (like 14C or LS7A) and then not take anything over summer, then have to jump back into it, just in case I forget stuff over summer.
by Sara_Lim_2C
Sun Feb 14, 2021 9:52 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Sapling Week 5/6: HW #8
Replies: 2
Views: 36

Re: Sapling Week 5/6: HW #8

So I believe this was how I did it: The total requires 3 parts: the deltaS of the water reaching boiling point, the deltaS of the water vaporizing, and the deltaS of the water cooling back down. So I used deltaS=nC v ln(T 2 /T 1 ), using 1 for n, 75.3 for C v , and plugged in the temperatures. Then ...
by Sara_Lim_2C
Sun Feb 14, 2021 9:33 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal vs Adiabatic
Replies: 6
Views: 18

Re: Isothermal vs Adiabatic

I believe isothermal means no change in temperature (deltaT=0), whereas adiabatic means there is no heat transfer with the surroundings (so q=0).
by Sara_Lim_2C
Sun Feb 14, 2021 9:32 pm
Forum: Student Social/Study Group
Topic: Fav Shows of the Moment
Replies: 104
Views: 257

Re: Fav Shows of the Moment

Julie and the Phantoms on Netflix! It's literally targeted at kids but it's just fun to watch!
by Sara_Lim_2C
Sun Feb 07, 2021 8:51 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Sapling #14 Week 3/4
Replies: 7
Views: 55

Re: Sapling #14 Week 3/4

I used w=-P(deltaV), so w=-(1.42atm)(7.66L-3.23L), then convert from L.atm to joules. Hope that helps!
by Sara_Lim_2C
Sun Feb 07, 2021 8:48 pm
Forum: Student Social/Study Group
Topic: Book Recommendations
Replies: 115
Views: 310

Re: Book Recommendations

Man I could write so many lists of book recs for different genres! Not sure what your preferred genres are but these are mine! For YA fantasy, the Angelfall trilogy and Six of Crows duology. For standalones that read like classics but are relatively recent, The Song of Achilles and All the Light We ...
by Sara_Lim_2C
Sun Feb 07, 2021 8:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Sapling Week 3/4 #11
Replies: 5
Views: 26

Re: Sapling Week 3/4 #11

I don't think you need H fus for this problem because ice isn't melting, it's just a piece of metal being submerged in water. I set it up by knowing that the heat lost by the metal is gained by the water, so q water = -q metal . From there, we can set mC(deltaT) = -mC(deltaT) and plug in all the val...
by Sara_Lim_2C
Sun Feb 07, 2021 8:29 pm
Forum: Calculating Work of Expansion
Topic: Sapling Problem #18
Replies: 1
Views: 14

Re: Sapling Problem #18

The relationship between constant‑pressure molar specific heat and constant‑volume molar specific heat is:

Cv = Cp - R

where R is the gas constant. Hope that helps!
by Sara_Lim_2C
Sun Feb 07, 2021 8:24 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Sapling week 3 and 4 #18
Replies: 5
Views: 28

Re: Sapling week 3 and 4 #18

We all have slightly different values for these problems, so I'm not sure exactly what your question is, but I solved the internal energy part using deltaU=(n)(Cv)(deltaT), knowing (Cv)=(Cp)-R. I hope that helps a little!
by Sara_Lim_2C
Sun Jan 31, 2021 10:42 pm
Forum: Phase Changes & Related Calculations
Topic: X2 vs 2X
Replies: 14
Views: 78

Re: X2 vs 2X

The reactant is X2, and the product is X, so the X-X bond is being broken to make 2 separate Xs. Since the bond is being broken, it's endothermic. Hope that helps!
by Sara_Lim_2C
Sun Jan 31, 2021 10:40 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Clarification on pKw
Replies: 14
Views: 39

Re: Clarification on pKw

From my knowledge pKw is always 14 at 25C.
by Sara_Lim_2C
Sun Jan 31, 2021 9:26 pm
Forum: Student Social/Study Group
Topic: Go treat yourself after MT1!
Replies: 75
Views: 304

Re: Go treat yourself after MT1!

After that midterm I spent the entirety of Saturday reading a book I'd been putting off to study for the midterm! It made me so happy to be able to read for fun again and it's definitely one of my new favorites :D
by Sara_Lim_2C
Sun Jan 31, 2021 9:21 pm
Forum: Student Social/Study Group
Topic: Students Who Have a Job
Replies: 79
Views: 336

Re: Students Who Have a Job

Because of covid, my hours were reduced A LOT, so I have been fortunately able to balance work and school. But sometimes I do wish I had more hours because I miss seeing a lot of my coworkers and just doing something outside of my house :/
by Sara_Lim_2C
Tue Jan 26, 2021 7:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Problem 6B.11
Replies: 1
Views: 13

Textbook Problem 6B.11

Hi there! I've been having trouble figuring out this problem: A student added solid Na2O to a volumetric flask of vol- ume 200.0 mL, which was then filled with water, resulting in 200.0 mL of NaOH solution. Then 5.00 mL of the solution was trans- ferred to another volumetric flask and diluted to 500...
by Sara_Lim_2C
Sun Jan 24, 2021 10:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pka, Ph, charged and neutral species
Replies: 7
Views: 54

Re: Pka, Ph, charged and neutral species

From my knowledge that's correct!
by Sara_Lim_2C
Sun Jan 24, 2021 10:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Neutral, unknown, or charged?
Replies: 6
Views: 46

Re: Neutral, unknown, or charged?

You'll have to compare the pH to the pKa. I believe for an acid, if the pH<pKa, it's neutral. If pH>pKa, it's charged. I believe it's vice versa for bases. Hope that helps!
by Sara_Lim_2C
Sun Jan 24, 2021 10:31 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Determining whether a reaction is Exothermic/Endothermic
Replies: 4
Views: 37

Re: Determining whether a reaction is Exothermic/Endothermic

You'll want to look at which bonds are being broken and formed in each reaction. For example, for a reaction like A2+B2-->(AB)2, you know that one A-A bond is being broken, one B-B bond is being broken, and two A-B bonds are being made. For my problem, A-B bonds are the strongest, then A-A and B-B. ...
by Sara_Lim_2C
Sun Jan 24, 2021 5:31 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Sapling Week 2 Problem 1
Replies: 8
Views: 34

Re: Sapling Week 2 Problem 1

Not necessarily! But it does help if you set up the equation: HA + H2O <-> H3O+ salt. It makes it a little easier for me to visualize it! Then you'll just do your ICE box as usual. Hope that helps!
by Sara_Lim_2C
Tue Jan 19, 2021 11:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: sapling #5 week 2
Replies: 3
Views: 28

Re: sapling #5 week 2

I started by using the pH to find the pOH, and from that the concentration of OH-. From there, that value will be equal to the change in [OH-] and [BH+], x. Then you can plug that x into Kb=(x^2)/(initial concentration-x) to solve for the initial concentration, and to get the percent protonation, di...
by Sara_Lim_2C
Sun Jan 17, 2021 10:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Week 1 #10
Replies: 8
Views: 36

Re: Sapling Week 1 #10

I'm pretty sure it's just (2.28)^2/0.463, and you just solve that.
by Sara_Lim_2C
Sun Jan 17, 2021 9:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Week 1 #3
Replies: 2
Views: 24

Re: Sapling Week 1 #3

I don't know exactly what your values were (because we all have slightly different ones) but I don't think it's changing after taking the square root. The denominator before taking the square root should be (0.800-x)^2, so it should be 0.800-x after taking it. The x's come from the Change part of yo...
by Sara_Lim_2C
Sun Jan 17, 2021 9:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: What makes a weak acid?
Replies: 11
Views: 49

Re: What makes a weak acid?

From my knowledge the only real specification for a weak acid (other than that it doesn't fully dissociate) is that it's not one of the strong ones :/ unfortunately I think memorizing the strong acids the way to go because I don't think we'll be told if they're strong or weak.
by Sara_Lim_2C
Sun Jan 17, 2021 4:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sampling #9
Replies: 2
Views: 28

Re: Sampling #9

I think we all have slightly different values for each question (even if they're the same problem). Could you by any chance post the full question?
by Sara_Lim_2C
Fri Jan 15, 2021 10:33 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: If P doubles
Replies: 4
Views: 23

Re: If P doubles

I believe the concentrations would also double. Because let's say you have 1 mole of a substance in a 2L container, the concentration would be 0.5M. And if you double the pressure (half the volume), that would be 1 mole in a 1 L container, and the concentration would be 1.0M. I think that's the righ...
by Sara_Lim_2C
Sun Jan 10, 2021 9:00 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q and K relationship
Replies: 12
Views: 67

Re: Q and K relationship

From my knowledge, when Q <K, that means the ratio of products/reactants is lower for Q than for K. That means that at the time you're calculating Q, there's more reactants than there would be at equilibrium. So since there's more reactants than there are at equilibrium, the reaction is more likely ...
by Sara_Lim_2C
Sun Jan 10, 2021 6:34 pm
Forum: Student Social/Study Group
Topic: Comfort Movies
Replies: 128
Views: 360

Comfort Movies

I was watching a Hunger Games movie marathon on TV and realized that although the subject matter is rather serious, I do enjoy watching those films. That got me thinking about comfort movies and those kinds that you can rewatch a million times and never get tired of. For me, those are the Hunger Gam...
by Sara_Lim_2C
Sun Jan 10, 2021 5:54 pm
Forum: Student Social/Study Group
Topic: Thoughts on Switching Majors?
Replies: 31
Views: 293

Re: Thoughts on Switching Majors?

I've spent many days considering switching to a geology major, which has honestly been a secret dream of mine for a long time. But I realized it would have wasted my entire first quarter because almost none of the classes I've taken would apply toward that major's requirements. I do intend to stick ...
by Sara_Lim_2C
Thu Jan 07, 2021 9:03 pm
Forum: Administrative Questions and Class Announcements
Topic: Follow Ups
Replies: 3
Views: 46

Re: Follow Ups

I believe so! Any related reply should count.
by Sara_Lim_2C
Thu Jan 07, 2021 8:57 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: reaction quotient Q vs. equilibrium constant K
Replies: 11
Views: 80

Re: reaction quotient Q vs. equilibrium constant K

From what I understand, Q is calculated the same way you calculate K, but it's used for any point in a reaction that isn't equilibrium.
by Sara_Lim_2C
Sat Dec 12, 2020 10:36 pm
Forum: Identifying Acidic & Basic Salts
Topic: What is a Salt?
Replies: 9
Views: 70

What is a Salt?

This feels like a dumb question, but what exactly is a salt? I know that they're the result of an acid-base neutralization reaction, but are there any other specifics about them?
by Sara_Lim_2C
Sat Dec 12, 2020 8:41 pm
Forum: Naming
Topic: Textbook 9C.1
Replies: 2
Views: 39

Re: Textbook 9C.1

The overall complex shown in 9C.1A has a negative 4- charge in my book. It's [Fe(CN)6]^4-. Were you looking at the right problem?
by Sara_Lim_2C
Sat Dec 12, 2020 8:37 pm
Forum: Amphoteric Compounds
Topic: Textbook 6A.17 (Metalloid Oxides)
Replies: 1
Views: 15

Re: Textbook 6A.17 (Metalloid Oxides)

From what I understand, they're both in that "staircase" of metalloids so they have both metallic and non-metallic traits, which allows them to act as acids or bases. I'm not exactly sure how they work, but I just kind of remember that the metalloids are usually amphoteric. Hope that helps!
by Sara_Lim_2C
Sat Dec 12, 2020 8:33 pm
Forum: Student Social/Study Group
Topic: Study music
Replies: 32
Views: 269

Re: Study music

I like listening to classic rock or punk rock while doing homework because half the time I can't understand the lyrics anyway, and the fast guitar keeps me awake. I recommend any of ZZ Top's early albums or All Time Low! I also like listen to video game soundtracks, like anything from Legend of Zeld...
by Sara_Lim_2C
Sat Dec 12, 2020 8:29 pm
Forum: Student Social/Study Group
Topic: Last Minute Breather
Replies: 10
Views: 101

Re: Last Minute Breather

My family put up our Christmas tree today, so that's nice! But overall I'm really stressed about this final tomorrow and I feel super unconfident in my understanding of some of the concepts :/ But my problem is that I don't know what I don't know! I don't know which things to study!
by Sara_Lim_2C
Sat Dec 12, 2020 8:20 pm
Forum: Conjugate Acids & Bases
Topic: Sapling 14
Replies: 6
Views: 75

Sapling 14

For an acid, I know that if pH<pKa the predominant species is neutral.

But for a base (sapling 14), is it reversed? Like a pH>pKa the predominant species is neutral?
by Sara_Lim_2C
Sun Dec 06, 2020 9:56 pm
Forum: Bronsted Acids & Bases
Topic: Strong & Weak Acid
Replies: 6
Views: 45

Re: Strong & Weak Acid

There are some ways, which Dr. Lavelle explains in Lecture #27. It mostly comes from looking at periodic table trends and bond lengths from those trends. Hope that helps!
by Sara_Lim_2C
Sun Dec 06, 2020 8:59 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 4
Views: 43

Re: Coordination Number

I think we do have to memorize what (en) and other shorthands for common ligands. For the first example, we should know that ethylenediamine is bidentate, so it will have two bonds to the central Platinum ion. And there's two of those, so that's four. And in addition, there's the 2 chlorine ions, so...
by Sara_Lim_2C
Sun Dec 06, 2020 8:27 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: How to find coordination number.
Replies: 10
Views: 70

Re: How to find coordination number.

The coordination number is equal to the number of bonds connected to the central atom. Hope that helps!
by Sara_Lim_2C
Sat Dec 05, 2020 5:33 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: textbook 6b.1
Replies: 2
Views: 18

Re: textbook 6b.1

I haven't done this yet, so I'm not sure if this is right, but if I were doing this problem, I would assume a volume of 100mL of HCl or something like that, and use M1V1=M2V2 to find the molar concentration of HCl in both the original 100mL and in the diluted version. There should be 1 mol of H+ for...
by Sara_Lim_2C
Thu Dec 03, 2020 9:07 pm
Forum: Coordinate Covalent Bonds
Topic: cyanide
Replies: 3
Views: 44

Re: cyanide

Cyanide doesn't have spacer atom(s) that allow the lone pairs on either side of the linear atom to bond to the transition metal. Because of that, only one of the lone pairs can bond to the transition metal.
by Sara_Lim_2C
Sat Nov 28, 2020 9:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling week 8 #17
Replies: 7
Views: 63

Re: Sapling week 8 #17

I don't think there's a specific rule for when they'd have that shape, I think it's just a possible structure.
by Sara_Lim_2C
Sat Nov 28, 2020 8:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling Week 7 and Week 8 Question 18
Replies: 7
Views: 93

Re: Sapling Week 7 and Week 8 Question 18

For one of the other questions for this problem, it asks "Select the carbon atom hybridizations that are represented in the structures drawn." Can someone explain how to go about determining the carbon hypridizations? Definitely! In Lecture 23, Lavelle went over how the number of regions ...
by Sara_Lim_2C
Sat Nov 28, 2020 8:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling Week 7 and Week 8 Question 18
Replies: 7
Views: 93

Re: Sapling Week 7 and Week 8 Question 18

So I believe the general idea is that if there's an even number of carbons, the hydrogens will be in the same plane. From my understanding, it's because in H2CCH2, the pi bond between C=C prevents the two carbon atoms from rotating, so the hydrogens are in the same plane. But with H2CCH2, the middl...
by Sara_Lim_2C
Sat Nov 28, 2020 1:14 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Preferential Interactions
Replies: 4
Views: 50

Re: Preferential Interactions

According to the whack notes I took, preferential interactions are caused when one side of the molecule is more likely to interact with a cation or anion because that side is more or less charged than the other. Non-polar molecules don't have preferential interactions, since in general they are symm...
by Sara_Lim_2C
Sat Nov 28, 2020 1:08 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling Week 7 and Week 8 Question 18
Replies: 7
Views: 93

Re: Sapling Week 7 and Week 8 Question 18

So I believe the general idea is that if there's an even number of carbons, the hydrogens will be in the same plane. From my understanding, it's because in H2CCH2, the pi bond between C=C prevents the two carbon atoms from rotating, so the hydrogens are in the same plane. But with H2CCH2, the middle...
by Sara_Lim_2C
Fri Nov 27, 2020 11:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: How do you know if atoms lie in the same plane?
Replies: 5
Views: 42

Re: How do you know if atoms lie in the same plane?

I believe it's primarily by the shape of the molecule. You can look at a molecular structure and see which ones are in the same plane based on where the atoms and lone pairs (places of electron density) lie. Hope that helps a little!
by Sara_Lim_2C
Tue Nov 24, 2020 8:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling Week 7/8 #18
Replies: 2
Views: 35

Sapling Week 7/8 #18

In this problem, we have to draw the structure for H2CCCCH2. I originally drew it with the four carbons arranged in a square, with double bonds between the two top carbons and the two on the bottom. On the left and right there were single bonds. On each of the carbons was a single bonded hydrogen. H...
by Sara_Lim_2C
Sun Nov 22, 2020 11:43 pm
Forum: Student Social/Study Group
Topic: Big Sad: Midterm 2
Replies: 86
Views: 960

Re: Big Sad: Midterm 2

To be honest, I was unsure on most of the questions. I made my best guess, but I was unconfident in most of my answers :/ I definitely think I could've done better.
by Sara_Lim_2C
Sun Nov 22, 2020 11:40 pm
Forum: Student Social/Study Group
Topic: Professor Lavelle's hat
Replies: 17
Views: 260

Re: Professor Lavelle's hat

After seeing this post I went straight to the lectures to see if I could read it, but nope not at all.
by Sara_Lim_2C
Sun Nov 22, 2020 8:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: atom rotating
Replies: 2
Views: 13

Re: atom rotating

I believe as the person above said, atoms with sigma bonds can rotate, but atoms with pi bonds can't. As for when an atom would rotate, I'm not quite sure about that either. I think they just have the ability to, but don't necessarily need it for any reason? I wonder if it might have to do with elec...
by Sara_Lim_2C
Sun Nov 22, 2020 7:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polarity of trans-dichlorethene
Replies: 4
Views: 26

Re: polarity of trans-dichlorethene

Since the chlorines are on opposite sides, the dipole moments cancel out.
by Sara_Lim_2C
Sun Nov 22, 2020 5:48 pm
Forum: Student Social/Study Group
Topic: Exercising Our Minds and Bodies
Replies: 120
Views: 642

Re: Exercising Our Minds and Bodies

My brother and I used to jump rope every day. Haven't gotten to recently, but I definitely should get back into it to make sure I do exercise!
by Sara_Lim_2C
Wed Nov 18, 2020 10:38 pm
Forum: Dipole Moments
Topic: Finding Dipole Moments in Multi-Element Molecules
Replies: 2
Views: 56

Finding Dipole Moments in Multi-Element Molecules

I'm having trouble figuring out why molecules like CH3Cl, CH2Cl2, and CHCl3 would have dipole-dipole interactions (according to textbook question 3F.3). I can find dipole moments in atoms that only have 2 elements (like SO2), but any more than that is a little confusing. Could anyone explain how to ...
by Sara_Lim_2C
Sun Nov 15, 2020 11:42 pm
Forum: Administrative Questions and Class Announcements
Topic: 14B and 14BL
Replies: 6
Views: 48

Re: 14B and 14BL

As someone already said, it's not required to take them simultaneously. I'm personally planning on taking 14B in winter and 14BL in spring, but it's up to you! And I think you technically can take classes that overlap if your professor is okay with making a separate final time, but it's very unlikel...
by Sara_Lim_2C
Sun Nov 15, 2020 11:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Structure plausibility
Replies: 5
Views: 39

Re: Structure plausibility

Yeah,I believe in general it's the structure that has the lowest total charge, but if you have structures with the same total charge, it's the one that has the least atoms with non-zero formal charges. It also has to do with electronegativity, as someone above already explained :D
by Sara_Lim_2C
Sun Nov 15, 2020 5:35 pm
Forum: Lewis Structures
Topic: Sapling #4
Replies: 5
Views: 36

Re: Sapling #4

I believe the one that contributes less is the one that has a higher energy, i.e. the one that is less stable. But since they have a seemingly equal total charge, you have to look at the structure and see which one has a higher separation of charge. For the carbamate ion example, the ion has a total...
by Sara_Lim_2C
Sun Nov 15, 2020 5:25 pm
Forum: Resonance Structures
Topic: Formal Charge
Replies: 11
Views: 104

Re: Formal Charge

From my knowledge, the least electronegative atom doesn't need to be at 0, but it just shouldn't be negative. I think a good rule of thumb is to stop whenever the formal charges and total charge are at the lowest they can be without the least electronegative atom being negative. I could be completel...
by Sara_Lim_2C
Sat Nov 14, 2020 7:52 pm
Forum: Resonance Structures
Topic: Oxidation numbers
Replies: 5
Views: 32

Re: Oxidation numbers

If you're looking for a resource on all the oxidation number rules, Sapling has a great one in their resources tab!
by Sara_Lim_2C
Sun Nov 08, 2020 9:41 pm
Forum: Lewis Structures
Topic: Lewis acids and bases
Replies: 10
Views: 76

Re: Lewis acids and bases

The acid is the molecule that accepts an electron pair, and the base is the molecule that donates an electron pair. Hope that helps a lil!
by Sara_Lim_2C
Sun Nov 08, 2020 9:39 pm
Forum: Student Social/Study Group
Topic: Mid-quarter Check in
Replies: 67
Views: 296

Re: Mid-quarter Check in

Some weeks are great, but some weeks I'm super stressed. Like this week I have 2 midterms (and one of them is two parts so it feels like 3), but last week I was doing absolutely nothing. But like someone else said I'm already counting down to Christmas!
by Sara_Lim_2C
Sat Nov 07, 2020 8:23 pm
Forum: Coordinate Covalent Bonds
Topic: Lewis Base Notation
Replies: 3
Views: 34

Lewis Base Notation

In Dr. Lavelle's Friday lecture, for some examples of Lewis Bases there was :NH3, F^-, and -OH. I know the two dots represent a lone pair, but why is the notation not NH3^-2 (like how Fluorine is F^-)? Also why does -OH have the negative in front of it instead of as a superscript? I mainly just wasn...
by Sara_Lim_2C
Sat Nov 07, 2020 8:18 pm
Forum: Trends in The Periodic Table
Topic: Easy Way to Remember Trends
Replies: 5
Views: 115

Re: Easy Way to Remember Trends

This is kinda off topic but I've never heard that acronym for wavelengths before. I heard Rabbits Mate In Very Unusually eXpensive Gardens lol. But like someone above said I remember that ionization energy increases toward the top right corner, and atomic radius increases to the bottom left corner. ...
by Sara_Lim_2C
Thu Nov 05, 2020 5:56 pm
Forum: Lewis Structures
Topic: Formal Charge
Replies: 5
Views: 28

Re: Formal Charge

I believe structures are most stable when the formal charge adds up to 0 (at least that's what I wrote in my lecture notes). If I'm wrong someone please correct me!
by Sara_Lim_2C
Sun Nov 01, 2020 8:59 pm
Forum: Trends in The Periodic Table
Topic: Sapling Question (Radius)
Replies: 10
Views: 68

Re: Sapling Question (Radius)

largest= Cs-, next is Cs, smallest is Cs+ The negative ion of Cs has the greatest radius because it has an extra electron which repels the existing electron, so the radius increases. The opposite occurs for Cs+. since it loses an electron, the entire 6th electron shell is empty, so the radius is sma...
by Sara_Lim_2C
Sun Nov 01, 2020 8:21 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum Number Memorizing tips
Replies: 2
Views: 12

Re: Quantum Number Memorizing tips

From my knowledge for remembering n and l (someone correct me if I'm wrong), the number (for example, the 3 in 3s^2) will be the value of n. Another example, 2p^4, n will be 2. As for l, l will depend on if it's in an s, p, d, or f orbital. So for s, l=0; for p, l=1; for d, l=2, etc. To use 2p^4 as ...
by Sara_Lim_2C
Sat Oct 31, 2020 11:08 pm
Forum: Student Social/Study Group
Topic: Favorite TV shows
Replies: 197
Views: 1249

Re: Favorite TV shows

At the moment, I love Julie and the Phantoms on Netflix! It's a literal kids show but I'm obsessed :D As for nostalgic shows, I love watching Danny Phantom on Hulu! (I guess I just have a thing for kids shows about ghosts lol)
by Sara_Lim_2C
Sat Oct 31, 2020 11:03 pm
Forum: Student Social/Study Group
Topic: Halloween!!!
Replies: 54
Views: 351

Re: Halloween!!!

I went to a park with my cousins (from a safe social distance) and took some cool photos with our Legend of Korra themed costumes (I was Asami)! I also played some Animal Crossing because the Halloween event is so cute!
by Sara_Lim_2C
Tue Oct 27, 2020 2:51 pm
Forum: Properties of Light
Topic: How to remember what v is in equations
Replies: 46
Views: 277

How to remember what v is in equations

Is there a good way to remember in which equations v=frequency versus when v=velocity? I keep getting them mixed up.
by Sara_Lim_2C
Sun Oct 25, 2020 9:49 pm
Forum: Administrative Questions and Class Announcements
Topic: what can we have during the midterm?
Replies: 5
Views: 29

Re: what can we have during the midterm?

There's a periodic table and a constants/equations sheet to print out. They're linked on Dr. Lavelle's website, but I'll link them below too! Constants/Equations: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/constants_equations.pdf Periodic Table: https://lavelle.chem.ucla.edu/w...
by Sara_Lim_2C
Sun Oct 25, 2020 9:48 pm
Forum: Administrative Questions and Class Announcements
Topic: what can we have during the midterm?
Replies: 5
Views: 29

Re: what can we have during the midterm?

There's a periodic table and a constants/equations sheet to print out. They're linked on Dr. Lavelle's website, but I'll link them below too! Constants/Equations: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/constants_equations.pdf Periodic Table: https://lavelle.chem.ucla.edu/w...
by Sara_Lim_2C
Sun Oct 25, 2020 7:15 pm
Forum: *Shrodinger Equation
Topic: Wave Function
Replies: 5
Views: 63

Re: Wave Function

I was wondering the same thing, commenting so I can find this post later
by Sara_Lim_2C
Sun Oct 25, 2020 7:14 pm
Forum: Administrative Questions and Class Announcements
Topic: midterm 1
Replies: 3
Views: 47

Re: midterm 1

I don't remember how many questions it is, but in answer to the post above this we have 50 minutes to take the midterm :)
by Sara_Lim_2C
Wed Oct 21, 2020 2:46 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Electron Example from Lecture 9
Replies: 4
Views: 51

Electron Example from Lecture 9

In the example Dr. Lavelle gave of the Heisenberg Indeterminacy Equation, it was determined that an electron couldn't possibly be contained to the nucleus because the uncertainty of the electron's velocity was higher than the speed of light. I understood the calculations and logic, but is it just co...
by Sara_Lim_2C
Mon Oct 19, 2020 11:49 pm
Forum: DeBroglie Equation
Topic: Deriving De Broglie Equation
Replies: 2
Views: 38

Re: Deriving De Broglie Equation

I think since we know E=pv, and we can substitute the v, velocity, for c, speed of light, because we're talking about photons (at least in the case of De Broglie's equation. And the speed of a photon is the speed of light, c. I'm not super sure about that but that was at least how I understood it :)
by Sara_Lim_2C
Wed Oct 14, 2020 2:09 pm
Forum: Einstein Equation
Topic: Wave Model Question
Replies: 5
Views: 86

Re: Wave Model Question

Disclaimer I'm still figuring this out too, but I think the reason we know it's not the wave model is because in theory, if light did follow the wave model, increasing the amplitude of the wave should increase the energy of the photons. However, when the intensity of the light was increased (increas...
by Sara_Lim_2C
Wed Oct 14, 2020 1:55 pm
Forum: Properties of Light
Topic: Lecture Music [ENDORSED]
Replies: 6
Views: 135

Re: Lecture Music [ENDORSED]

Definitely loved the music too! It's such a nice way to start class :D
by Sara_Lim_2C
Fri Oct 09, 2020 10:02 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Standard Number of Digits for Avogadro's Number?
Replies: 5
Views: 64

Standard Number of Digits for Avogadro's Number?

For Avogadro's number I usually use 6.02x10^23. However when I was doing some textbook problems all my answers were somewhat far off because the textbook solutions use 6.022x10^23. Is there a way to know how specific we need to get for this constant? For example should it match the amount of signifi...
by Sara_Lim_2C
Fri Oct 09, 2020 12:25 pm
Forum: Molarity, Solutions, Dilutions
Topic: What does mmol stand for?
Replies: 33
Views: 378

Re: What does mmol stand for?

As for micromole vs millimole (the post 3 above mine), yes I believe micromole is µmol, and millimole is mmol :)
by Sara_Lim_2C
Fri Oct 09, 2020 12:09 pm
Forum: SI Units, Unit Conversions
Topic: Rounding
Replies: 20
Views: 166

Re: Rounding

A friend of mine heard this rounding rule in her chemistry class (not at UCLA): "If the digit removed is 5, the preceding number increases by 1 if it is odd and remains the same if it is even: 17.75----->17.8; 17.65----->17.6" Neither of us had ever heard of it before, has anyone else? Is ...
by Sara_Lim_2C
Fri Oct 09, 2020 12:04 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8838
Views: 1497112

Re: Post All Chemistry Jokes Here

What do you do with a sick chemist? If you can't curium, and you can't helium, you might as well barium.

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