Search found 114 matches

by Annie Chantasirivisal_4G
Thu Mar 12, 2020 8:07 pm
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 275
Views: 120211

Re: Saying Thank You to Dr. Lavelle

Dearest Dr. Lavelle, Thank you so much for a wonderful 2 quarters of chemistry! I have never met any professor who was this passionate about student success and having access to resources outside of class. Going into the 14 series I wasn't too excited because since I never took AP chem, I felt that ...
by Annie Chantasirivisal_4G
Thu Mar 12, 2020 7:54 pm
Forum: Student Social/Study Group
Topic: Class Grading
Replies: 44
Views: 1098

Re: Class Grading

Is it possible to get a lower letter grade after the curve? For example, if I have a 450/500 (90%), is it possible that I'll get a B+ because the class average is too high? He doesn't curve down, only up! Even if the class average was high, he'll just use a straight scale at that point and make 90%...
by Annie Chantasirivisal_4G
Thu Mar 12, 2020 7:48 pm
Forum: General Science Questions
Topic: Study guide 4th Q
Replies: 2
Views: 51

Re: Study guide 4th Q

Posting the question for reference: Screen Shot 2020-03-12 at 10.51.51 PM.png The cathode here is aluminum (E naught = -1.66V) and anode is magnesium (E naught = -2.36V). When subtracting, Ecell= E cathode - E anode, so -1.66V - (-2.36V) is +0.70V. The negatives cancel out. Perhaps you were confused...
by Annie Chantasirivisal_4G
Thu Mar 12, 2020 7:40 pm
Forum: Administrative Questions and Class Announcements
Topic: Equation Sheet on Final
Replies: 2
Views: 26

Re: Equation Sheet on Final

I'm not too sure either because finals and midterms usually have formula sheets separate from the front cover where we put our names, so I would print one out from Dr. Lavelle's website before the test just in case!
by Annie Chantasirivisal_4G
Thu Mar 12, 2020 7:37 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: What was your favorite chem topic?
Replies: 24
Views: 110

Re: What was your favorite chem topic?

Coordination compounds were such a pain to memorize at first, but after I memorized how to do them I felt like I could actually vibe with chem. Still slightly disappointed that they never appeared in our 14A final, haha.

Also, like many people have commented, chemical equilibrium <3!
by Annie Chantasirivisal_4G
Thu Mar 12, 2020 7:29 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: higher entropy cis or trans
Replies: 8
Views: 1017

Re: higher entropy cis or trans

Is this something that was covered in class or we should know for the midterm? Sorry for the late reply, but as you can tell it was not on the midterm. This is just a review of 14A with cis and trans placement, but I think we'll get into more detail of it during 14C and D with O-chem :> Edit: Sorry...
by Annie Chantasirivisal_4G
Tue Mar 10, 2020 10:50 pm
Forum: Administrative Questions and Class Announcements
Topic: Coronavirus Concern
Replies: 6
Views: 160

Re: Coronavirus Concern

I'm sure it's been a stressful night for all of us... since the Chancellor's email, I've just been constantly worried about the possibility of having an online final... I have really bad eyesight as it is and I'm really concerned about the strain of having to stare at a computer screen for three hou...
by Annie Chantasirivisal_4G
Mon Mar 09, 2020 10:24 pm
Forum: Administrative Questions and Class Announcements
Topic: ENDGAME Review Session
Replies: 71
Views: 2173

Re: ENDGAME Review Session

Thank you for all of your hard work these past three years, Lyndon!! King of chemistry congrats on graduating we'll all miss u dearly <3333
by Annie Chantasirivisal_4G
Mon Mar 09, 2020 10:17 pm
Forum: Ideal Gases
Topic: Liter to meter cubed?
Replies: 4
Views: 42

Re: Liter to meter cubed?

Subashni Rajiv 1K wrote:I like to use this acronym to help me remember the order of prefixes:
King Henry Died By Drinking Chocolate Milk
Kilo Hecto Deka Base Deci Centi Milli


That's genius, thank you!!
by Annie Chantasirivisal_4G
Sat Mar 07, 2020 8:35 pm
Forum: First Order Reactions
Topic: Negative sign in ln [A]t = -k t + ln [A]o
Replies: 2
Views: 43

Negative sign in ln [A]t = -k t + ln [A]o

For the formula ln [A]t = -k t + ln [A]o,

why is there a negative sign when t=-(1/k) ln[A]t/ln[A]o
but not when t=(1/k) ln[A]o/ln [A]t?
by Annie Chantasirivisal_4G
Sat Mar 07, 2020 5:28 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 7A.15
Replies: 3
Views: 51

7A.15

Screen Shot 2020-03-07 at 5.18.26 PM.png I'm a little confused about this question; I know that when trying to find the order of each reactant you look for experiments where only one thing has changed (in this case find one difference and two similarities since there are three reactants) but for th...
by Annie Chantasirivisal_4G
Sat Mar 07, 2020 2:32 pm
Forum: Administrative Questions and Class Announcements
Topic: Notes on 3/04/20 (wednesday)
Replies: 2
Views: 47

Re: Notes on 3/04/20 (wednesday)

Samuel G Rivera - Discussion 4I wrote:That section in the notes reads "Step 1 must be the rate determining (slowest) step, since overall rate is proportional to the concentration of [NO2]^2.
Slowest step determines rate of reaction: rate = k1[NO2]^2"


Thank you so much!! I really appreciate it :>!
by Annie Chantasirivisal_4G
Fri Mar 06, 2020 9:13 pm
Forum: Administrative Questions and Class Announcements
Topic: Notes on 3/04/20 (wednesday)
Replies: 2
Views: 47

Notes on 3/04/20 (wednesday)

Hi! I missed what was written on a slide towards the end of lecture on 3/04/20... The line before it reads, "Step 1 must be the rate determining (slowest) step, since overall rate is proportional to the concentration of NO2." Next line is what I missed, "Slowest step determines...&quo...
by Annie Chantasirivisal_4G
Sun Mar 01, 2020 4:35 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Deriving the Nernst Equation
Replies: 3
Views: 36

Deriving the Nernst Equation

Hello, I was practicing how to derive the Nernst Equation and got a little confused... I know you use ΔG°= -nFE° and ΔG= ΔG°+ RTlnQ in order to obtain the Nernst equation, E = E°- (RT/nF)lnQ, however I'm stuck on the difference between the E and E° in the equation. When obtaining E°(inside), I used ...
by Annie Chantasirivisal_4G
Sat Feb 29, 2020 4:24 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.7b
Replies: 2
Views: 53

Re: 6N.7b

When you write out the half reactions, you will find the anode as H2(g) -> 2H+(aq) +2e- and the cathode as 2H+(aq) + 2e- -> H2(g). When you put them together to find the balanced overall equation, you get 2H+(aq) -> 2H+(aq), where the H2 and e- cancel out from both sides. In this case, you would ne...
by Annie Chantasirivisal_4G
Thu Feb 27, 2020 8:58 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.7b
Replies: 2
Views: 53

6N.7b

Screen Shot 2020-02-27 at 8.56.36 PM.png


For part b, why is n=1? when balanced, shouldn't there be two e- from 2H+ + 2e- -> H2?
by Annie Chantasirivisal_4G
Wed Feb 26, 2020 9:47 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 7th edition 6N.1
Replies: 4
Views: 157

Re: 7th edition 6N.1

For part b, why does the solutions manual use n=2 instead of n=1 since there is only 1 mol of e- transfer? For K, I got 1x10^2 instead of 1x10^4. I got that (1x10^2) too! I thought the solutions manual had an error because there can only be 1 electron transfer in order to go from In3+ to In2+ and f...
by Annie Chantasirivisal_4G
Tue Feb 25, 2020 11:14 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.7, standard potential
Replies: 1
Views: 34

6M.7, standard potential

6M.7: Arrange the following metals in order of increasing strength as reducing agents for species in aqueous solution: (a) Cu, Zn, Cr, Fe; (b) Li, Na, K, Mg; (c) U, V, Ti, Al; (d) Ni, Sn, Au, Ag. How would we know which standard potential to use? For example, in (a) Cu has two values: Cu+ + e- --> C...
by Annie Chantasirivisal_4G
Tue Feb 25, 2020 9:34 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.5
Replies: 4
Views: 80

Re: 6M.5

Would we ever add anything other than solid platinum?
by Annie Chantasirivisal_4G
Fri Feb 21, 2020 10:58 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: How to find n in ΔG°= -nFE°
Replies: 2
Views: 53

How to find n in ΔG°= -nFE°

6L.1 Calculate the standard reaction Gibbs free energy for the following cell reactions: (a) 2 Ce4+(aq) + 3 I−(aq) →2 Ce3+(aq) + I3−(aq), E cell°=+1.08V (b) 6 Fe3+(aq) + 2 Cr3+(aq) + 7 H2O(l) → 6 Fe2+(aq) + Cr2O72−(aq) + 14 H+(aq), E cell°=−1.29V I'm still having trouble finding n when given a redox...
by Annie Chantasirivisal_4G
Wed Feb 19, 2020 8:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Midterm Q6B
Replies: 5
Views: 74

Midterm Q6B

For which process will ∆H^o and ∆G^o be expected to be most similar to 2H2(g) + 2Cl2(g) → 4 HCl(g), with ∆H^o = –92.3 kJ? (A) 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s) (B) 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) (C) 2NO2(g) → N2O4(g) (D) 2H2(g) + O2(g) → 2H2O(g) Why is the answer A? How do we approach this...
by Annie Chantasirivisal_4G
Wed Feb 19, 2020 8:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Midterm 3B
Replies: 2
Views: 72

Midterm 3B

Which combination of solutions of HCl and NaOH would produce the largest ∆T? (A) 50 mL of 1 M HCl with 50 mL of 1 M NaOH (B) 50 mL of 2 M HCl with 50 mL of 2 M NaOH (C) 100 mL of 1 M HCl with 50 mL of 2 M NaOH (D) 100 mL of 1 M HCl with 100 mL of 1 M NaOH I honestly did not understand how to approac...
by Annie Chantasirivisal_4G
Wed Feb 19, 2020 8:02 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Answer is different for 5G.15
Replies: 5
Views: 47

Re: Answer is different for 5G.15

I also got -2.7 kJ/mol. For -RTlnK I got -12349.86 J/mol, and for RTlnQ I got 9612.98 J/mol, so shouldn't their sum be -2736.87 J/mol or -2.7 kJ/mol?
by Annie Chantasirivisal_4G
Wed Feb 19, 2020 7:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: midterm 3C
Replies: 4
Views: 55

Re: midterm 3C

Just to add, although NH4+ is a weak acid, it can still affect the pH of the solution, just not as much as a strong acid.
by Annie Chantasirivisal_4G
Fri Feb 14, 2020 5:55 pm
Forum: Balancing Redox Reactions
Topic: Redox reaction
Replies: 5
Views: 48

Re: Redox reaction

The way I like to visualize it is by separating the molecules by element in order to determine their oxidation numbers. For reference: 8H+ + MnO4- + 5Fe2+ -> Mn2+ + 5Fe3+ + 4H2O Oxygen and Hydrogen remained the same because when you separate them in H2O on the right, you can see that there are two H...
by Annie Chantasirivisal_4G
Fri Feb 14, 2020 5:23 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: higher entropy cis or trans
Replies: 8
Views: 1017

Re: higher entropy cis or trans

IMG_0853 2.jpg I drew them out so that it's easier to visualize the 12 cis and the 3 trans in case anyone is also struggling like me; the above comment definitely helped me understand this problem a lot better, thank you so much! I circled the X so that it's easier to see how each molecule differs ...
by Annie Chantasirivisal_4G
Tue Feb 11, 2020 2:37 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: higher entropy cis or trans
Replies: 8
Views: 1017

Re: higher entropy cis or trans

IMG_0853 2.jpg I drew them out so that it's easier to visualize the 12 cis and the 3 trans in case anyone is also struggling like me; the above comment definitely helped me understand this problem a lot better, thank you so much! I circled the X so that it's easier to see how each molecule differs ...
by Annie Chantasirivisal_4G
Tue Feb 11, 2020 1:34 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 4F13
Replies: 3
Views: 50

Re: 4F13

Since both parts have to do with phase change, you can use dS = q/T = dH/T. Thus, the calculation is 1.00 mol(-6.01 kJ/mol)/273.15 K. And, the answer is -0.0220 kJ/K. For part b, you can use the same equation. First, calculate the moles of ethanol and multiply it by the molar enthalpy of vaporizati...
by Annie Chantasirivisal_4G
Tue Feb 11, 2020 1:20 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: HW 4F.1
Replies: 5
Views: 64

Re: HW 4F.1

Actually I figured it out, it's because the system is losing energy and the surroundings are gaining energy, (-deltaSsys = deltaSsurr). Hi, I was also confused about the same thing, but based on your explanation, the information provided in the problem allows us to find the entropy of the system (y...
by Annie Chantasirivisal_4G
Thu Feb 06, 2020 10:05 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: S = q/T
Replies: 1
Views: 27

Re: S = q/T

The magnitude of entropy takes both heat transfer and temperature into consideration, though. Based on the ratio of q/T alone, if there was an increase in temp, then the denominator will become bigger, but if the amount of heat transferred stayed the same you will end up with a smaller entropy. Simi...
by Annie Chantasirivisal_4G
Thu Feb 06, 2020 9:56 pm
Forum: Administrative Questions and Class Announcements
Topic: Step Up Sessions
Replies: 15
Views: 1139

Re: Step Up Sessions

for anyone that's been, have you found them helpful/how is the pace of the step-up sessions I've only been to Lyndon's and Melody's sessions, but I also agree that they are very useful and helpful! They both make worksheets for their sessions, but Lyndon's is a workshop, so he gives you time to wor...
by Annie Chantasirivisal_4G
Thu Feb 06, 2020 9:41 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 1 Distribution
Replies: 9
Views: 108

Re: Test 1 Distribution

Like everyone else has said, there is no curve, but if it helps my TA said the average of her sections was around 36/50 for test 1, so I'm thinking the overall average is somewhere around there. I don't recommend comparing yourself to others as it can get really discouraging and everyone learns at a...
by Annie Chantasirivisal_4G
Tue Feb 04, 2020 1:51 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4.15
Replies: 2
Views: 74

Re: 4.15

As a follow-up to this question, does anyone know why the heat capacity is presented as -4.184J.C^-1.g^-1 instead of it being positive when calculating change in temperature? My answer differs from the solution manual because of this.
by Annie Chantasirivisal_4G
Tue Feb 04, 2020 1:47 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4.15
Replies: 2
Views: 74

Re: 4.15

In H = -153.89 + 2(-167.16) -2(-167.16)-0, -153.89 + 2(-167.16) is ZnCl2; since the enthalpy of formation of ZnCl2 is not in the table, you combine Zn2+ (-153.89) and 2Cl- (2(-167.16)) to get ZnCl2. -2(-167.16) is HCl, which looks the same as Cl- because the enthalpy of formation of H+ is 0. That la...
by Annie Chantasirivisal_4G
Sat Feb 01, 2020 3:42 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Material
Replies: 13
Views: 102

Re: Midterm Material

One thing I'd like to point out is the very wonderful practice sheet/problem sets that UA Lyndon always makes before a midterm/final. His review sheet contained almost every type of problem you might encounter in the test, and it definitely helped me out very much last quarter; if you go to his revi...
by Annie Chantasirivisal_4G
Mon Jan 27, 2020 8:54 pm
Forum: Administrative Questions and Class Announcements
Topic: 14A Final Answer Key
Replies: 5
Views: 72

14A Final Answer Key

Hello! Does anyone know if there will be an answer key released for the 14A final exam? I lost a couple of points here and there and I'm just curious as to what my answer should have been or how far away I was from getting it right :">
by Annie Chantasirivisal_4G
Mon Jan 27, 2020 8:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Negative delta H
Replies: 2
Views: 31

Negative delta H

Hi, I am still a bit confused on ΔH(rxn); so I understand that when you are given a reaction and its ΔH and you need its reverse reaction for combining reactions you make ΔH negative, for ex. with N2(g) + O2(g) -> 2NO(g) and ΔH= 180.6 kJ, you'd use ΔH=-180.6 kJ for 2NO(g) -> N2(g) + O2(g). However, ...
by Annie Chantasirivisal_4G
Mon Jan 27, 2020 8:38 pm
Forum: Administrative Questions and Class Announcements
Topic: final exam
Replies: 6
Views: 92

Re: final exam

In case anyone has this thread bookmarked/subscribed, you can still pick up your exams during week 4! I just got mine today and there were still a bunch of unclaimed exams left. Go soon, though!
by Annie Chantasirivisal_4G
Mon Jan 27, 2020 8:36 pm
Forum: Administrative Questions and Class Announcements
Topic: Fall Quarter Final?
Replies: 12
Views: 146

Re: Fall Quarter Final?

Hey guys! I just went to pick up my exam today and there are still a bunch left in room 3034, and I still got to keep mine.
by Annie Chantasirivisal_4G
Sat Jan 25, 2020 2:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6B.9, Kw
Replies: 3
Views: 42

Re: 6B.9, Kw

I found this on a different thread:

“Any [H30+] over 1 will have a negative pH, because the -log(1)= 0, because 10^0=1.”

I must’ve missed the - sign when I solved it initially, then? If it’s negative then it’s a superacid.
by Annie Chantasirivisal_4G
Sat Jan 25, 2020 2:22 pm
Forum: Administrative Questions and Class Announcements
Topic: Grading of Tests
Replies: 18
Views: 142

Re: Grading of Tests

I agree, I’m pretty sure partial credit is given based on the steps you’ve taken; every step taken towards the answer is allotted a specific number of points until you reach the final answer, which would give you full points if correct, so the earlier you mess up the less points you’ll be given.
by Annie Chantasirivisal_4G
Sat Jan 25, 2020 2:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6B.9, Kw
Replies: 3
Views: 42

Re: 6B.9, Kw

I think the answer is wrong for i) pH. When you do pH = -log([H+]) = -log(1.50) = -0.176 but the answer in the solution manual is 0.176 I looked back at my old solutions to see what I got when I did the problem last week and I got the positive number, but now that I plugged in -log(1.5) into my cal...
by Annie Chantasirivisal_4G
Sat Jan 25, 2020 2:12 pm
Forum: Administrative Questions and Class Announcements
Topic: homework for week 4
Replies: 11
Views: 107

Re: homework for week 4

So far the things I’m reading from the thermochemistry unit, particularly 4A, I cannot recall learning or having been done in class... are topics like expansion work something we should have already learned or will Dr. Lavelle go over this later next week?
by Annie Chantasirivisal_4G
Wed Jan 22, 2020 9:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6B.9, Kw
Replies: 3
Views: 42

6B.9, Kw

Screen Shot 2020-01-22 at 9.11.20 PM.png When I was doing this problem, I wanted to try using Kw=[H3O+][OH-] for extra practice with that formula, however the concentration I got for [OH-] in i. when using the Kw formula was different from the concentration I got when using [OH-]=10^-pOH. Is this b...
by Annie Chantasirivisal_4G
Wed Jan 22, 2020 9:15 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 6B 9
Replies: 3
Views: 49

Re: 6B 9

Yes, they are called superacids and superbases! "Super" in this case meaning they exist beyond the standard pH scale of 1 to 14 that we are accustomed to. I don't think this class will deal with them much, aside from the fact that we know they exist.
by Annie Chantasirivisal_4G
Sun Jan 19, 2020 3:05 pm
Forum: Administrative Questions and Class Announcements
Topic: PLFs on MLK?
Replies: 1
Views: 44

PLFs on MLK?

Hello,

Since tomorrow is a holiday, I just wanted to make sure: are peer learning sessions in Covel canceled tomorrow night?
by Annie Chantasirivisal_4G
Thu Jan 16, 2020 8:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5l.29
Replies: 5
Views: 39

Re: 5l.29

I have a followup question: Why did you all decide to set x = to change in equilibrium for H2 or Cl2, and 2X = change in HCL instead of saying x = change in HCL and 0.5X = change in H2 and Cl2? I did it the second way and I got the wrong answer. I'm trying to understand conceptually why my way is w...
by Annie Chantasirivisal_4G
Wed Jan 15, 2020 8:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test 1
Replies: 1
Views: 32

Re: Test 1

I can't find these concepts in my notes either, but a UA said that Dr. Lavelle could use these concepts in terms of reactions at equilibrium. Like for ATP hydrolysis, the reaction could be written as ATP ⇌ ADP + phosphate group, etc.
by Annie Chantasirivisal_4G
Wed Jan 15, 2020 8:20 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5l.29
Replies: 5
Views: 39

Re: 5l.29

Hi! The way I did it is by setting up the ice table, which will end up with HCl having 0.22-2x, and H2 and Cl2 each having x at equilibrium. Then, you plug those values into where they would go in the equilibrium constant ((PH2)(PCl2))/((PHCl)^2) which gives you x^2/(0.22-2x)^2 is equal to K, 3.2 x ...
by Annie Chantasirivisal_4G
Mon Jan 13, 2020 10:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.39
Replies: 4
Views: 76

5.39

"In an experiment, 0.020 mol NO2 was introduced into a flask of volume 1.00 L and the reaction 2NO2(g)⇌N2O4(g) was allowed to come to equilibrium at 298 K. (a) Using information in Table 5G.2, calculate the equilibrium concentrations of the two gases. (b) The volume of the flask is reduced to h...
by Annie Chantasirivisal_4G
Mon Jan 13, 2020 9:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K vs Kc
Replies: 2
Views: 23

K vs Kc

So, I understand the distinction between Kp and Kc, one for partial pressure and the other for concentration, but for table 5G.2, what is their difference? How would we know whether to use K or Kc when being referred to it by a textbook problem (such as 5.39)?
IMG_0115.jpg
by Annie Chantasirivisal_4G
Mon Jan 13, 2020 9:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework 5.35
Replies: 3
Views: 40

Re: Homework 5.35

IMG_0113.jpg

(That's the graph in case anyone needs it, hopefully I attached it right ><)

I'm still a bit confused on how to write the balanced equation... how can you tell from the graph that there were 2 moles A, 1 mol B, and 2 moles C??
by Annie Chantasirivisal_4G
Sat Jan 11, 2020 6:01 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Adding inert gas [ENDORSED]
Replies: 9
Views: 66

Re: Adding inert gas [ENDORSED]

Will helium always be the inert gas we would add, or what other gases could also work?
by Annie Chantasirivisal_4G
Sat Jan 11, 2020 5:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Simplifying cubic equations
Replies: 3
Views: 26

Simplifying cubic equations

Will we always be given a small K in order to simplify cubic equations in this class?

If K was big, how do you go about solving a cubic equation?
by Annie Chantasirivisal_4G
Sat Jan 11, 2020 5:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Thermodynamically Stable
Replies: 3
Views: 43

Re: Thermodynamically Stable

Cl2 is more stable than F2 because there was less dissociation from Cl2 to Cl atoms. When comparing the two reactions, Cl2 ended up with an essentially unchanged concentration of 0.0010 mol.L^-1, while the concentration of Cl atoms at equilibrium was 1.1 x 10^-5 mol.L^-1; on the other hand, F2 had a...
by Annie Chantasirivisal_4G
Sat Jan 11, 2020 5:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Aqueous state [ENDORSED]
Replies: 1
Views: 29

Aqueous state [ENDORSED]

When calculating the equilibrium constant, we omit liquids and solids because their concentrations are either insignificant or there is no such thing as their concentration. However, how do we treat aqueous solutions? What is different about aqueous solutions from liquids that prevent it from gettin...
by Annie Chantasirivisal_4G
Mon Jan 06, 2020 7:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Post assessment part 2
Replies: 1
Views: 41

Post assessment part 2

The equilibrium constant, KP, for the reaction SO2 (g) + O2 (g) ⇌ SO3 (g) at 700 K is 3 x 10^4. A mixture of SO2, O2, and SO3, each at 65 bars was introduced into a container at 700 K. Is the reaction at equilibrium? If not, does SO3 tend to form or decompose? I'm having trouble understanding this q...
by Annie Chantasirivisal_4G
Sat Dec 07, 2019 9:22 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4484

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

MMckinney_4H wrote:For number 34, why are two moles of OH produced for every mole of CaO?


CaO separates into Ca^2+ and O^2-, and O^2- can be added with H2O to form 2OH-, thus 1 mole of CaO ends up producing 2 moles of OH-.
by Annie Chantasirivisal_4G
Sat Dec 07, 2019 5:49 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4484

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

For mini marshmallow 2c, why is the coordination number for K[Cu(en)2(CN)2] 6? It is six because en is a bidentate, so it will bind at two areas; since there are two en, that would mean 4 binding sites, in addition to the 2 cyanides, for a total of 6 bonds bound to copper, thus coordination number 6.
by Annie Chantasirivisal_4G
Sat Dec 07, 2019 3:51 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4484

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

Hey guys, he just posted marshmallow answers rn. posting in case anyone has it bookmarked/subscribed.
by Annie Chantasirivisal_4G
Sat Dec 07, 2019 3:33 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelating vs Polydentate Ligands
Replies: 3
Views: 73

Re: Chelating vs Polydentate Ligands

A chelating ligand is one that binds to a cation in more than one location, thus it is polydentate. Some of the common polydentate ligands are oxalate (bidentate) ethylenediamine (bidentate) diethylenetriamine (tridentate) ethylenediaminetriacetate (EDTA - hexadentate) porphyrin (tetradentate) I do...
by Annie Chantasirivisal_4G
Sat Dec 07, 2019 3:23 pm
Forum: Administrative Questions and Class Announcements
Topic: Main focus
Replies: 3
Views: 51

Re: Main focus

Based on Dr. Lavelle's review of past final exam questions, I think the topics are all spread pretty evenly amongst the 8 questions, so I don't think material post-midterm would have a higher emphasis on the final. Anything in our notes/his slides is fair game :')
by Annie Chantasirivisal_4G
Sat Dec 07, 2019 3:17 pm
Forum: Naming
Topic: Molecular formula for long ligands
Replies: 2
Views: 31

Molecular formula for long ligands

Sorry if this has been asked already but I can't find the answer :c Does anyone know if in the final we are allowed to use abbreviations of long ligands such as (en) instead of NH2CH2CH2NH2 when writing out the molecular formulas from being given the name of the coordination compounds? For example, ...
by Annie Chantasirivisal_4G
Sat Dec 07, 2019 3:07 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4484

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

For #17, what does it mean by the “hybridization of each lone pair”? Is it supposed to be the hybridization of each central atom? Can someone answer this please! I am wondering the same thing. Hybridization of lone pairs can be determined by looking at the atom that the lone pairs are attached to. ...
by Annie Chantasirivisal_4G
Sun Dec 01, 2019 8:27 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Sig Figs for pH
Replies: 1
Views: 23

Sig Figs for pH

The book states: "A Note on Good Practice: The number of digits following the decimal point in a pH value is equal to the number of significant figures in the corresponding molar concentration, because the digits preceding the decimal point simply report the power of 10 in the data (as in log 1...
by Annie Chantasirivisal_4G
Fri Nov 29, 2019 7:12 pm
Forum: Bronsted Acids & Bases
Topic: Trichloroacetic acid vs acetic acid
Replies: 2
Views: 39

Re: Trichloroacetic acid vs acetic acid

Trichloroacetic acid is just acetic acid with 3 Cl atoms instead of 3 H. Therefore, the Cl atoms have a stronger pull on the bonds of the carboxyl group, loosening the OH bond and making H+ions more likely to dissociate. When the bonds of the carboxyl group are pulled, are all of the bonds loosenin...
by Annie Chantasirivisal_4G
Fri Nov 29, 2019 6:46 pm
Forum: General Science Questions
Topic: hydrogen vs hydronium
Replies: 5
Views: 59

Re: hydrogen vs hydronium

The hydrogen ion is often used in place of hydronium to simplify things. However, you should know that the hydronium ion better represents what is actually seen. Right, thank you! In reference to what is "actually seen", are you referring to hydronium in an acid? Like when a hydrogen ion ...
by Annie Chantasirivisal_4G
Fri Nov 29, 2019 6:43 pm
Forum: General Science Questions
Topic: hydrogen vs hydronium
Replies: 5
Views: 59

Re: hydrogen vs hydronium

Nevermind, just saw in my notes that hydronium is H3O+, which is completely different from hydrogen, H. Sorry!
by Annie Chantasirivisal_4G
Fri Nov 29, 2019 6:39 pm
Forum: General Science Questions
Topic: hydrogen vs hydronium
Replies: 5
Views: 59

hydrogen vs hydronium

This is probably a silly question, but I often hear Dr.Lavelle mentioning hydronium ion during lecture in place of hydrogen so I just wanted to make sure, hydronium and hydrogen are interchangeable names, right? Or is there a difference in structure somehow that I'm not catching?

Thanks!
by Annie Chantasirivisal_4G
Fri Nov 29, 2019 6:33 pm
Forum: Bronsted Acids & Bases
Topic: Trichloroacetic acid vs acetic acid
Replies: 2
Views: 39

Trichloroacetic acid vs acetic acid

Hi,

I did not quite catch Dr.Lavelle's explanation for why trichloroacetic acid was a stronger acid than acetic acid... does anyone understand why?
by Annie Chantasirivisal_4G
Wed Nov 20, 2019 7:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2.63
Replies: 1
Views: 27

2.63

Estimate the bond angles of peroxyacetylnitrate. *I don't know how to attach an image sorry :c* Does anyone understand why angle b has to be 109.5 degrees? I can see that the other two angles are trigonal planar so it explains the 120 degrees, which I assumed also applied to angle b, but since oxyge...
by Annie Chantasirivisal_4G
Wed Nov 20, 2019 7:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Octahedral
Replies: 6
Views: 55

Octahedral

Hi, this might be a silly question, but does anyone know why an octahedral is an octahedral? Where does the 8 from "octa-" come from if there are only 6 atomic orbitals?
by Annie Chantasirivisal_4G
Wed Nov 20, 2019 7:09 pm
Forum: General Science Questions
Topic: Chem BL
Replies: 7
Views: 105

Re: Chem BL

Does anyone know if it also applies to 14CL? Like should we take CL after we take 14C as well?
by Annie Chantasirivisal_4G
Wed Nov 20, 2019 7:04 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: lewis structure of organic compunds
Replies: 5
Views: 58

Re: lewis structure of organic compunds

For instance, CH3CH2OH. How would I know how to draw this compound? So, that compound is composed of carbon, hydrogen and oxygen atoms. Of the three, their electronegativities, from lowest to highest, are H<C<O. Usually the most electropositive element goes to the middle, but since hydrogen can onl...
by Annie Chantasirivisal_4G
Wed Nov 20, 2019 6:39 pm
Forum: Biological Examples
Topic: Cisplatin
Replies: 2
Views: 49

Re: Cisplatin

Cisplatin has two chlorine atoms on one side that allow it to bind to one of the nitrogens in the nucleotide base guanine, specifically N7 of guanine, that has a lone pair. When those chlorine atoms form two bonds (each forming a bond), it's a lot more difficult for cell division to occur and thus t...
by Annie Chantasirivisal_4G
Sun Nov 17, 2019 6:39 pm
Forum: Hybridization
Topic: 2.57
Replies: 1
Views: 27

2.57

Hello! Just wanted to check my work since this problem's answer was not in the solutions manual. 2.57: Acetonitrile, CH3CN, is used as a solvent in the pharmaceutical industry. Describe the structure of the CH3CN molecule in terms of hybrid orbitals, bond angles, and σ- and π-bonds. The N atom is a ...
by Annie Chantasirivisal_4G
Sat Nov 16, 2019 4:13 pm
Forum: Dipole Moments
Topic: Cancelling dipole moments
Replies: 9
Views: 124

Cancelling dipole moments

I'm having trouble visualizing how dipole moments cancel each other out for molecules that have more than two dipoles. I can kind of see how the C-Cl bonds in trans-dichloroethene cancel out, since they're on opposite sides and their vectors are going in opposite directions, but how do I visualize t...
by Annie Chantasirivisal_4G
Sat Nov 16, 2019 4:04 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: lewis structure of organic compunds
Replies: 5
Views: 58

Re: lewis structure of organic compunds

Do you have an example of a difficult compound? I'm assuming most homework problems use easier compounds, but whenever they get challenging for me or if I get it wrong initially, I just start off again with evaluating the most electropositive element and putting it in the middle, then spread out the...
by Annie Chantasirivisal_4G
Sat Nov 16, 2019 3:24 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: biological examples?
Replies: 3
Views: 32

Re: biological examples?

There's two hydrogen bonds in the Adenine and Thymine base pair, and three hydrogen bonds in the Guanine and Cytosine base pair.

Hydrogen bonding also plays a role in maintaining the shape of proteins, DNA, RNA, cellulose, etc.
by Annie Chantasirivisal_4G
Thu Nov 14, 2019 7:41 pm
Forum: General Science Questions
Topic: Midterm
Replies: 2
Views: 36

Re: Midterm

You are not limited to your TA, you can go to other TAs as well. The solutions are also online on the class website, so if you feel like maybe you missed out on points you should compare answers with the solutions to see how yours differ.
by Annie Chantasirivisal_4G
Thu Nov 14, 2019 7:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Homework 2E.1
Replies: 4
Views: 43

Re: Homework 2E.1

Since 2E.1 already gives us the shape of the molecule, would we have to find what molecule fits that shape when you "draw it out" to see the lone pairs?
by Annie Chantasirivisal_4G
Fri Nov 08, 2019 5:59 pm
Forum: Lewis Structures
Topic: Hybridization
Replies: 2
Views: 43

Hybridization

Why do electrons undergo hybridization?
Just had discussion today and was totally confused by the end of it... In the BH3 example, my TA drew an electron from Boron in the 2s state going up into the 2p state... why does it do that?
by Annie Chantasirivisal_4G
Fri Nov 08, 2019 5:51 pm
Forum: Bond Lengths & Energies
Topic: negative Ep
Replies: 5
Views: 58

negative Ep

Does anyone understand why Ep is always negative for interaction potential energy?

I missed Dr. Lavelle's explanation... why does a negative Ep lead to attractive force?
by Annie Chantasirivisal_4G
Fri Nov 08, 2019 5:45 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: Dispersion
Replies: 3
Views: 28

Re: Dispersion

The way I understood it, because there were different amounts of carbon in each substance, that affected the number of electrons since the more carbons (or even just atoms in general) that you have, the more electrons there will be. In the interaction potential energy equation we went over in class ...
by Annie Chantasirivisal_4G
Fri Nov 08, 2019 5:36 pm
Forum: Student Social/Study Group
Topic: Midterm
Replies: 3
Views: 66

Re: Midterm

It's difficult to explain because I don't remember the question word for word, but I found it really similar to the first question on the practice exam Dino Nuggets that UA Lyndon made where you're given molecules and you try to find mass percentage composition from there. I think it'd be helpful to...
by Annie Chantasirivisal_4G
Tue Nov 05, 2019 8:42 pm
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic quantum number (m sub l)
Replies: 1
Views: 39

Magnetic quantum number (m sub l)

Hi guys, So I understand that the magnetic quantum number (m l ) can be found based on the angular momentum quantum number (l), where you just go from -l to +l, but I wanted to make sure... will m l =-1 always correspond to the x, such as if we were given n=2, l=1, and m l =-1 the referred state is ...
by Annie Chantasirivisal_4G
Sat Nov 02, 2019 3:24 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: What d to include when "counting valence electrons including d electrons"
Replies: 1
Views: 32

What d to include when "counting valence electrons including d electrons"

How do we know which d to include when counting valence electrons from electron configuration when they want us to include d electrons? For example, in 2A.1a Sb has an electron configuration of [Kr]4d10 5s2 5p3 but its valence electrons are only 5 electrons, while in 2A.1c Mn has an electron configu...
by Annie Chantasirivisal_4G
Tue Oct 29, 2019 11:30 pm
Forum: Lewis Structures
Topic: 2B.3d
Replies: 1
Views: 25

2B.3d

The question asks to draw lewis structures for BrF3. The answer drew Br with 10 valence electrons (three single bonds each connecting to F, and then two pairs of electrons at the non bonded side of Br at the top), but I do not understand why. I know it has something to do with being an exception to ...
by Annie Chantasirivisal_4G
Tue Oct 29, 2019 11:18 pm
Forum: Lewis Structures
Topic: Homework 2A 12
Replies: 3
Views: 43

Re: Homework 2A 12

The M in M2+ also refers to the metal with the charge 2+, so the book is asking for metals/elements with a charge of 2+ that work with the various electron configurations you listed.
by Annie Chantasirivisal_4G
Tue Oct 29, 2019 11:13 pm
Forum: Lewis Structures
Topic: 2B. 1C
Replies: 5
Views: 62

Re: 2B. 1C

Continuing from this, how would we know which atom would be the central atom? The book stated that "usually" the central atom would be listed first, but for ONF this clearly was not the case... how could we tell from the "usually" and exceptions?
by Annie Chantasirivisal_4G
Tue Oct 29, 2019 11:00 pm
Forum: Administrative Questions and Class Announcements
Topic: Sapling Learning
Replies: 3
Views: 46

Re: Sapling Learning

Hey! I got an email about it, but it made it seem like everyone needs to trade in the code sleeve at the UCLA store? Do you know if this only applies to the people that SaplingLearning doesn't work for? Or should we all be trading in the code sleeve because SaplingLearning will be inactive after Oc...
by Annie Chantasirivisal_4G
Sat Oct 26, 2019 2:25 pm
Forum: Ionic & Covalent Bonds
Topic: Atomic Radius
Replies: 4
Views: 58

Re: Atomic Radius

Atomic radii decrease from left to right because going across a period is essentially adding another electron in the same shell/energy level; the next element would also have an increase nucleus since protons and neutrons are also being added to cancel out charges. Thus, that increase in nuclear cha...
by Annie Chantasirivisal_4G
Sat Oct 26, 2019 2:14 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Noble Gas Configuration
Replies: 2
Views: 31

Re: Noble Gas Configuration

I'm pretty sure that since we've been doing noble gas configurations in class examples, they would be acceptable for the test.
by Annie Chantasirivisal_4G
Sat Oct 26, 2019 12:07 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E. 21
Replies: 1
Views: 33

Re: 1E. 21

Hi, The question you posted was for 1E.20, but I'll try to answer it; to find the number of valence electrons, it would be handy to have a periodic table with you where you can look at the placement of the element, and then determine the electron configuration from there. For example, (a)Ta has an e...
by Annie Chantasirivisal_4G
Mon Oct 21, 2019 7:14 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Hw 1B.27
Replies: 3
Views: 75

Hw 1B.27

"A bowling ball of mass 8.00 kg is rolled down a bowling alley lane at 5.00 ± 5.0 ms^-1. What is the minimum uncertainty in its position?" I didn't notice the additional "5.00 ±" in the question when I tried solving the problem at first, however I got the same answer as the book;...
by Annie Chantasirivisal_4G
Mon Oct 21, 2019 7:07 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Hw 1B.25 and ℏ symbol
Replies: 1
Views: 57

Hw 1B.25 and ℏ symbol

Does anyone understand 1B.25? “What is the minimum uncertainty in the speed of an electron confined within a lead atom of diameter 350. pm? Model the atom as a one-dimensional box with a length equal to the diameter of the actual atom.” I started off using Heisenberg’s uncertainty equation (delta p ...
by Annie Chantasirivisal_4G
Mon Oct 21, 2019 6:59 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electrostatic potential energy
Replies: 2
Views: 49

Electrostatic potential energy

I was reviewing my notes from last week, and I'm having trouble understanding this equation:

electrostatic potential energy ∝ (q1*q2)/r

what does each variable mean, and what type of problem would require us to use it?
by Annie Chantasirivisal_4G
Sat Oct 19, 2019 3:58 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Memorizing electron configuration
Replies: 3
Views: 56

Re: Memorizing electron configuration

https://www.chem.fsu.edu/chemlab/chm1045/e_config.html ^^^^ This website has a straightforward visual or how to remember the order of the electron configuration; what helped me remember the order is by writing the sublevels in order, with each number going down in column and the spdf across the row....
by Annie Chantasirivisal_4G
Sat Oct 19, 2019 3:47 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: S and D orbitals
Replies: 1
Views: 40

Re: S and D orbitals

Chromium and Copper are the only two exceptions where you would have to switch between the s and d orbitals. These two elements prefer to have a full or half full d sub-level because it is more stable than to have a d sub-level that's partially filled, so an electron from the 4s orbital would rise t...

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