Search found 79 matches

by Rachel Kho Disc 2G
Sun Feb 14, 2021 10:36 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Sapling Week 5/6 Q#8
Replies: 5
Views: 60

Re: Sapling Week 5/6 Q#8

So when you're solving using the different steps, you use the equations deltaS = Cpmln(Tf/Ti), where when Cpm is for liquid water and this is an increase in temperature, Tf should be 100 degrees Celsius and Ti should be whatever is given to you in the problem. Then, you use the same equation where C...
by Rachel Kho Disc 2G
Sun Feb 14, 2021 10:26 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Sapling #6
Replies: 6
Views: 32

Re: Sapling #6

Solving this problem takes three steps

Step 1: find the change in entropy due to volume by using the equation nRln(V2/V1). R=8.3145 J/mol*K.
Step 2: find the change in entropy due to temperature by using the equation nCvmln(T2/T1).
Step 3: Add up the answers to steps 1 and 2.

Hope this helps!
by Rachel Kho Disc 2G
Sun Feb 14, 2021 9:04 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Sapling #8 Week 5-6
Replies: 4
Views: 19

Sapling #8 Week 5-6

I know there are three steps to solving this problem, and that you need to calculate Step 1: deltaS = Cpm (liquid water) ln (Tf/Ti) Step 2: deltaS vapor, which is given in the problem Step 3: deltaS = Cpm(water vapor) ln (Tf/Ti) And then you add all these values up. But for some reason I can't get t...
by Rachel Kho Disc 2G
Sun Feb 14, 2021 8:48 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sapling W5-6 Q15
Replies: 6
Views: 41

Re: Sapling W5-6 Q15

All your steps seem to be correct, but make sure that when you are finding the values for deltaH and deltaS total, you are manipulating the second equation so that:

A + B --> 2C
1) A + B --> 2D
2) 2D --> 2C

Also, they ask for your answer in kJ so don't forget to convert!
by Rachel Kho Disc 2G
Sun Feb 14, 2021 7:57 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: sapling #5
Replies: 10
Views: 62

Re: sapling #5

Hmmm yeah I had trouble with this initially as well, and I figured out that I forgot to take the natural log. Your methods seem to be correct, first solving for n using PV/RT, R being 8.3145 J/mol*K and T being 298 K. Then after converting your given temperatures from Celsius to Kelvin, input your n...
by Rachel Kho Disc 2G
Sun Feb 07, 2021 10:28 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Atoms, Linear, Non- Linear Molecules?
Replies: 9
Views: 50

Re: Atoms, Linear, Non- Linear Molecules?

Yup we have to go back to Chem 14A and Lewis dot structures and VSEPR theory. Carbon dioxide is considered a linear molecule, so if you're referring to #20 on the sapling week 3&4 homework, you should be using the 5/2R Cvm.
by Rachel Kho Disc 2G
Sun Feb 07, 2021 10:11 pm
Forum: Calculating Work of Expansion
Topic: Sapling #18
Replies: 3
Views: 30

Re: Sapling #18

I actually think that according to whatever type of molecule you're given, we all have different given ways of calculating Cp and Cv. So for your problem, since your Cp = 4R, that would be 4(8.3145 J/mol*K). Cv = (your number for Cp)-8.3145, and then input that into the equation delta U = n(Cv)(delt...
by Rachel Kho Disc 2G
Sun Feb 07, 2021 9:39 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Sapling HW Week 3/4 #20
Replies: 5
Views: 36

Re: Sapling HW Week 3/4 #20

Can someone also clarify how to tell whether something is an atom, linear, or nonlinear molecule? Is it just the Lewis dot structures?
by Rachel Kho Disc 2G
Sun Feb 07, 2021 7:58 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Sapling Week 3/4 #13
Replies: 8
Views: 43

Re: Sapling Week 3/4 #13

This is work done on a system, so you need to make sure that there are more moles of gas on the products than reactants side (i.e. w=-delta n * R * T). In the problem you're specifically talking about, there are only solids on the reactants side (no gas) and one mole of gas on the product side, so t...
by Rachel Kho Disc 2G
Sun Jan 31, 2021 10:18 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Stable Form in Enthalpies of Formation
Replies: 11
Views: 43

Re: Stable Form in Enthalpies of Formation

Just memorizing that diatomic gases are in their most stable forms, and that solid carbon (graphite) is in its most stable form, will be enough. If the problem comes up during an exam and the element is not one of these ones that we've stated, the question will tell us whether or not it is in its mo...
by Rachel Kho Disc 2G
Sun Jan 31, 2021 10:11 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: percent protonation/deprotonation
Replies: 14
Views: 112

Re: percent protonation/deprotonation

What helped me when I was also confused about this concept was remembering from Chem 14A that a Bronsted acid is one that donates a proton, and a Bronsted base is one that receives the proton. So the only difference between deprotonization and protonization is whether or not the substance in questio...
by Rachel Kho Disc 2G
Sun Jan 31, 2021 9:50 pm
Forum: Phase Changes & Related Calculations
Topic: Endothermic v. Exothermic
Replies: 107
Views: 393

Re: Endothermic v. Exothermic

I'm pretty sure that there will be no exceptions to the fact that delta H is positive and negative for endothermic and exothermic reactions, respectively. Other things to keep in mind when differentiation between the two include: Endothermic - energy absorbed - bonds broken - strong reactant bonds E...
by Rachel Kho Disc 2G
Sun Jan 31, 2021 9:47 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Sapling Week 3/4 #6
Replies: 14
Views: 90

Re: Sapling Week 3/4 #6

You could solve this problem thinking about the [bonds broken]-[bonds formed], but there is a much easier and faster way to figure this out. Just remember that a combustion reaction usually consists of x compound + O2(g) --> CO2(g) + H2O(l)!
by Rachel Kho Disc 2G
Sun Jan 31, 2021 5:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K vs. Kc
Replies: 36
Views: 130

Re: K vs. Kc

I was also confused when doing the homework for this since they give you a table and there are different values for each, but Kc is used for concentration and Kp for partial pressure. On the midterm I think there will only be one value given and you won't have to differentiate or anything.
by Rachel Kho Disc 2G
Sun Jan 24, 2021 11:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Week 2 Sapling #3
Replies: 4
Views: 68

Re: Week 2 Sapling #3

So you've already been able to solve for x using the quadratic equation. You could say that [H+] is x, so to get pH you calculate [H+]=-log(your x value). To get the pOH, you just subtract this value from 14. Then to get the percent ionization, you divide your x value by the given M solution * 100%.
by Rachel Kho Disc 2G
Sun Jan 24, 2021 10:38 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: sapling week 2 #5
Replies: 15
Views: 118

Re: sapling week 2 #5

You're given the pH, and you subtract this value from 14 to get the pOH. You've already found that 10^-pOH gives you your [OH-] which you can set as x. Kb (given) = x^2/[B]initial-x [B]initial = (x^2/8.333*10^-5) + x Percentage protonated = (x/[B]initial)*100% Hope this helps you visualize the next ...
by Rachel Kho Disc 2G
Sun Jan 24, 2021 10:31 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Qudratic Formula
Replies: 19
Views: 163

Re: Qudratic Formula

My most common mistakes whenever I get back that the calculator has received an error have been that I inputted a number wrong, I forgot to add plus and minus signs when necessary, or I forgot to square b. So definitely check to make sure that these aren't your problems!
by Rachel Kho Disc 2G
Sun Jan 24, 2021 9:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #2 Week 2
Replies: 5
Views: 26

Sapling #2 Week 2

Sapling Week 2 #2 The Ka of a monoprotic weak acid is 0.00439. What is the percent ionization of a 0.102 M solution of this acid? When solving this problem, I set up 1.2*10^-4 = x^2/0.75-x. I tried to make the assumption that x was insignificant and could be crossed out, but the feedback said that t...
by Rachel Kho Disc 2G
Sun Jan 24, 2021 11:48 am
Forum: Administrative Questions and Class Announcements
Topic: Lyndon's Worksheets?
Replies: 1
Views: 57

Lyndon's Worksheets?

Hey does anyone know if Lyndon Bui posted a midterm review packet like he did the Marshmallow and Dino Nugget packets for 14A? I could really use some more practice resources!
by Rachel Kho Disc 2G
Sun Jan 17, 2021 9:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #10, WK 1
Replies: 8
Views: 92

Re: Sapling #10, WK 1

I'm also confused about the last part of this question, and I'm especially having a lot of trouble solving for x using the quadratic equation. My numbers are a bit different, so at equilibrium [N2O4] = 0.32 + x, and [NO2] = 2.89 - 2x. My K value is 11.16. So what I have so far: K = [2.89-2x]^2/0.32...
by Rachel Kho Disc 2G
Sun Jan 17, 2021 9:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sampling Week 1 #2
Replies: 12
Views: 152

Re: Sampling Week 1 #2

I would first start with making an ICE chart and solving for the initial molarity of 2SO3 by dividing the given moles by the given volume. Then you can start filling out your ice chart. The question gives you the final moles and by dividing that by the 3 L, you get the change in molarity/x. With th...
by Rachel Kho Disc 2G
Sun Jan 17, 2021 8:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #10, WK 1
Replies: 8
Views: 92

Re: Sapling #10, WK 1

I'm also confused about the last part of this question, and I'm especially having a lot of trouble solving for x using the quadratic equation. My numbers are a bit different, so at equilibrium [N2O4] = 0.32 + x, and [NO2] = 2.89 - 2x. My K value is 11.16. So what I have so far: K = [2.89-2x]^2/0.32 ...
by Rachel Kho Disc 2G
Sun Jan 17, 2021 5:12 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Sapling Week 1 #6
Replies: 7
Views: 61

Re: Sapling Week 1 #6

Also, once you solve for Q through [P]/[R], the question asks what direction the reaction shifts in order to reach equilibrium. To do this, you have to remember that if Q < K (K should already be given), there will be a shift towards products. If Q > K, the reaction will shift towards reactants. If ...
by Rachel Kho Disc 2G
Sun Jan 17, 2021 4:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solving for x on Sapling (and in general!)
Replies: 3
Views: 29

Solving for x on Sapling (and in general!)

I always have trouble for solving for x after having done ice tables and setting up the equation and trying to do the quadratic formula. On sapling questions 3 and 4 especially, I definitely think I'm calculating something wrong. Can anyone help walk me through how to solve for x in an easier way? S...
by Rachel Kho Disc 2G
Sun Jan 10, 2021 11:29 pm
Forum: Ideal Gases
Topic: n/V = concentration
Replies: 19
Views: 167

Re: n/V = concentration

Concentration is simply moles/liters, which, if you remember from 14A is the same as moles of solute(n)/volume of solution(v), which is equal to molarity(M).
by Rachel Kho Disc 2G
Sun Jan 10, 2021 10:49 pm
Forum: Ideal Gases
Topic: Kc vs Kp
Replies: 109
Views: 1076

Re: Kc vs Kp

Also will we need to have the formula that converts Kc to Kp memorized? Or will that be given to us on an equations sheet?
by Rachel Kho Disc 2G
Sun Jan 10, 2021 10:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.1
Replies: 4
Views: 46

Re: 5G.1

Yes, if I'm not mistaken, the pressure of the reactant increases, and the equilibrium constant increases, so the answer is false. The equilibrium constant only depends on temperature, not pressure. However, I'm also unsure as to how to know if Q increases or decreases.
by Rachel Kho Disc 2G
Sun Jan 10, 2021 7:48 pm
Forum: General Science Questions
Topic: midterm/final
Replies: 12
Views: 96

Re: midterm/final

Yeah on the main course website, there's a note at the bottom of the site info page that says all students need to download Respondus which is available at [link given], so it's reasonable to assume that the format and exam proctoring will be the same. I'm not sure if we'll need to download a new ve...
by Rachel Kho Disc 2G
Sun Jan 10, 2021 5:46 pm
Forum: Student Social/Study Group
Topic: Chemistry Community
Replies: 29
Views: 161

Re: Chemistry Community

I know my TA from 14A said that the deadline was by Sunday each week. I hadn't heard of anyone being able to make up points as long as they had 50 by the end of the quarter, but I could be wrong! I think it would probably be best to get all your posts in by Sunday just to be safe.
by Rachel Kho Disc 2G
Sun Dec 13, 2020 1:07 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity and Bond Angle
Replies: 2
Views: 15

Polarity and Bond Angle

I have a lot of trouble measuring bond angles (it's either a hit or miss with them--I can usually figure it out intuitively from the molecular shape, but I get mixed up with which one is <109.5 and <120, etc.). Does anyone know how to memorize those or do I just use quizlet flashcards to quickly mem...
by Rachel Kho Disc 2G
Sat Dec 12, 2020 8:39 pm
Forum: Naming
Topic: Textbook 9C.1
Replies: 2
Views: 51

Textbook 9C.1

For example 9C.1a, why is it called iron ferrate if the overall complex is positive? Is it because iron itself is an exception like gold and silver and copper? Also, when do you know to add ‘ion’ at the end? I thought the rule was that if the overall compound was positive, then you would put ‘ion’ a...
by Rachel Kho Disc 2G
Sat Dec 12, 2020 8:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Textbook 2E.13
Replies: 1
Views: 26

Textbook 2E.13

Lewis Structure of N2O I know the answer because I checked the solutions manual, but can someone walk me through how to get the Lewis structure for N2O? Why wouldn’t there be a lone pair on the central N atom and then a single bond to the other N with two lone pairs? Is it because the outside N woul...
by Rachel Kho Disc 2G
Sat Dec 12, 2020 11:48 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Finding Bond Angle
Replies: 3
Views: 41

Re: Finding Bond Angle

When thinking about nitrogen as the central atom, it might also be helpful to look at it as a trigonal pyramidal shape, which you should have automatically memorized to know that it is <109.5, or 107 as it states here.
by Rachel Kho Disc 2G
Fri Dec 11, 2020 10:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Why is CH2Cl2 polar
Replies: 6
Views: 62

Re: Why is CH2Cl2 polar

Wait so does this also mean that tetrahedral molecules are usually polar? Are there any examples of nonpolar tetrahedral molecules?
by Rachel Kho Disc 2G
Sun Dec 06, 2020 11:59 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation Number
Replies: 5
Views: 10

Re: Oxidation Number

I believe the oxidation number should be 3+!
by Rachel Kho Disc 2G
Sun Dec 06, 2020 11:57 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Finding Coordination Numbers
Replies: 7
Views: 90

Re: Finding Coordination Numbers

Yeah I'm having trouble with this question on sapling #5, for [CO](NH3)5(H2O)]Cl3. Does anyone have any tips?
by Rachel Kho Disc 2G
Sun Dec 06, 2020 11:49 pm
Forum: Naming
Topic: Sapling Question #5
Replies: 3
Views: 18

Sapling Question #5

I'm having trouble with monodentate and bidentate ions, especially on question #5 on sapling when it asks for the coordination number for metal species. I'm having trouble with answering the question for [Co(en)2(CO)2Br].
by Rachel Kho Disc 2G
Sun Dec 06, 2020 11:36 pm
Forum: Naming
Topic: Naming Coordination Compound
Replies: 4
Views: 46

Re: Naming Coordination Compound

Some general rules are: 1) ligands metal 2) ligand --> replace -ite with -o or -ido (if neutral, same name as molecule except for specific things we have to memorize such as OH2 or EDTA) 3) number of ligands --> greek prefixes 4) order ligands alphabetically 5) for central atom, if overall charge is...
by Rachel Kho Disc 2G
Sun Dec 06, 2020 11:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Memorizing Molecular Geometry
Replies: 6
Views: 39

Re: Memorizing Molecular Geometry

I heard this as well! Also, does anyone have any tips for memorizing molecular geometry??? It just seems very intimidating to look at sometimes.
by Rachel Kho Disc 2G
Sun Nov 29, 2020 8:25 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: delocalized pi bond
Replies: 8
Views: 113

Re: delocalized pi bond

Delocalized pi bonds occur in molecules that have resonance structures in which the double or triple bonds can be drawn in different locations between atoms. The electrons are free to move over more than two nuclei.
by Rachel Kho Disc 2G
Sun Nov 29, 2020 8:17 pm
Forum: Sigma & Pi Bonds
Topic: Sapling Q #16
Replies: 14
Views: 169

Re: Sapling Q #16

You would need to first discern which molecules have double or triple bonds (which have one pi bond and two pi bonds, respectively). Of these molecules, you would then determine whether or not there are resonance structures in which the double or triple bonds can be moved around. If that is the case...
by Rachel Kho Disc 2G
Sun Nov 29, 2020 6:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: sapling #12
Replies: 13
Views: 144

Re: sapling #12

Carbon and oxygen should both be able to fill out the octet, meaning the carbon most likely has four bonds, three of which are hydrogen and one of which is oxygen. That means that the last hydrogen should be connected to the oxygen. So now you have two bonds on the oxygen, and you can't make any mor...
by Rachel Kho Disc 2G
Sun Nov 29, 2020 6:38 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration for Transition Metals
Replies: 3
Views: 51

Electron Configuration for Transition Metals

I’m a little lost in my understanding of electron configuration and orbital diagrams for transition metals and charged particles, especially in terms of Focus 2A. (ex. 2A.3a, 2A.5, 2A.19b, 2A.19d, 2A.21d). Could someone help explain how to figure out these types of problems?
by Rachel Kho Disc 2G
Sun Nov 29, 2020 6:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling Week 7/8 HW #12
Replies: 8
Views: 109

Re: Sapling Week 7/8 HW #12

This is a review of the first test! If you, like me, are more of a step-by-step visual learner, then it might help to note that the stoichiometric conversions for carbon, as an example, are (37.5 g C/1) * (1 mol/12.011 g C) = 3.122 mol C. Then you do the same steps for oxygen and hydrogen, divide al...
by Rachel Kho Disc 2G
Sat Nov 21, 2020 9:28 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ground State vs. Excited State
Replies: 6
Views: 106

Ground State vs. Excited State

I’m having some trouble understanding ground state electron configurations versus excited state electron configurations. When looking at the orbital diagram, how are you able to tell the difference between the two? What exactly goes into the orbital diagram of an excited state electron? This concept...
by Rachel Kho Disc 2G
Sat Nov 21, 2020 9:18 pm
Forum: Lewis Structures
Topic: Central Atom Question
Replies: 20
Views: 165

Re: Central Atom Question

H will never be the central atom because as others stated before it can only form one bond, and additionally it's useful to put whatever atom has the lowest ionization energy as the central atom (this tactic doesn't work all the time but it is usually a good starting point).
by Rachel Kho Disc 2G
Sat Nov 21, 2020 9:15 pm
Forum: Electronegativity
Topic: Electronegativity difference
Replies: 8
Views: 80

Re: Electronegativity difference

I think it's important to remember that H is a weird case. Hydrogen bonds are such exceptionally strong cases of dipole-dipole bonds because there is a great electronegativity difference between H and the other atom, and the H must bond to N, O, and F which all have very high electronegativities. In...
by Rachel Kho Disc 2G
Sat Nov 21, 2020 9:04 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: What are orbitals?
Replies: 10
Views: 153

Re: What are orbitals?

It might also be useful to note that in places where there are "blind spots", there is 0 electron density and an electron cannot be located in these areas. These places are called nodes, and there are two types: radial (spherical) and angular (angular). On a coordinate plane, these are whe...
by Rachel Kho Disc 2G
Sat Nov 21, 2020 8:38 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Exercise 2A.5
Replies: 3
Views: 37

Exercise 2A.5

There are some electron configurations with [Xe]4f145d106s2. Where exactly is the 4f14 coming from? I thought it might be the lanthanides and actinides, but I counted 15 columns and not 14 columns, so I'm a little confused.
by Rachel Kho Disc 2G
Sun Nov 15, 2020 8:48 pm
Forum: Resonance Structures
Topic: Sapling #9 part b
Replies: 2
Views: 12

Re: Sapling #9 part b

I got answer D in response to this question, because if the experimental value is 144 pm which is close to the 140 average expected value for the Cl-O double bond, then there should be 4 double bonds. However, answer C (which has 3 double bonds and 1 single bond) is also correct because the feedback...
by Rachel Kho Disc 2G
Sun Nov 15, 2020 7:46 pm
Forum: Bond Lengths & Energies
Topic: Sapling #4
Replies: 4
Views: 64

Sapling #4

I'm not exactly sure what is meant by bond character in one of the parts to sapling 4? I eventually got to the right answer because by comparing the experimental bond lengths to the ones given in the table and deducing that because experimental single bonds are less than the expected, the double bon...
by Rachel Kho Disc 2G
Sun Nov 15, 2020 7:18 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling #20
Replies: 12
Views: 102

Re: Sapling #20

A hydrogen bond is any bond wherein a hydrogen atom is bonded to another highly electronegative atom, namely N, O, or F. Even though a C-H bond has a hydrogen in it, a carbon-hydrogen bond is not considered a hydrogen bond because there isn't a huge difference in electronegativity between carbon and...
by Rachel Kho Disc 2G
Sun Nov 15, 2020 7:09 pm
Forum: Ionic & Covalent Bonds
Topic: midterm 2: knowing compounds
Replies: 14
Views: 107

Re: midterm 2: knowing compounds

I agree that we most likely wouldn't need to know nomenclature for the midterm, but I think it's still a good idea to at least be somewhat familiar with knowing polyatomic ions.
by Rachel Kho Disc 2G
Sun Nov 15, 2020 7:07 pm
Forum: Dipole Moments
Topic: Sapling #13
Replies: 9
Views: 98

Re: Sapling #13

Make sure you count the hydrogen bonds that are already in the urea molecule, because that's where I made a mistake. Initially, I only counted the hydrogen bonds that COULD form and so it took me a few tries to get to the right answer.
by Rachel Kho Disc 2G
Sun Nov 08, 2020 9:37 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Radial vs Angular Nodes
Replies: 2
Views: 34

Re: Radial vs Angular Nodes

You can visualize it on a coordinate plane by thinking that places where the wave crosses the axis is a node. There, you have a zero chance of finding an electron. Radial nodes are spherical and have zero electron density, whereas angular nodes are planar with zero electron density.
by Rachel Kho Disc 2G
Sun Nov 08, 2020 9:33 pm
Forum: Quantum Numbers and The H-Atom
Topic: Textbook 1D #21
Replies: 5
Views: 35

Re: Textbook 1D #21

A tip my TA gave me was super helpful in understanding the relationship between l and s,p,d,f orbitals. when l = 0 --> s when l = 1 --> p when l = 2 --> d when l = 3 --> f a) l = 2 corresponds to the d orbital. b) l = 0 corresponds to the s orbital. c) l = 2 corresponds to the d orbital. d) l = 3 co...
by Rachel Kho Disc 2G
Sun Nov 08, 2020 9:29 pm
Forum: Quantum Numbers and The H-Atom
Topic: Textbook 1D #13
Replies: 3
Views: 22

Re: Textbook 1D #13

A tip my TA gave me was super helpful! for l: l = 0 --> s l = 1 --> p l = 2 --> d l = 3 --> f for ml: l = 0 --> ml = 1 l = 1 --> ml = 3 l = 2 --> ml = 5 l = 3 --> ml = 7 a) given n = 7, values of l can be from 0 --> 6, which means that including 0 there are 7 possible values. b) given 6d, d correspo...
by Rachel Kho Disc 2G
Sun Nov 08, 2020 9:13 pm
Forum: Student Social/Study Group
Topic: midterm 1
Replies: 10
Views: 116

Re: midterm 1

It's also super helpful to just drill the homework problems! Make sure you are able to complete the homework correctly without looking at your notes. The solutions should be on Sapling under Atkins 7e SSM.
by Rachel Kho Disc 2G
Sun Nov 08, 2020 9:10 pm
Forum: Properties of Light
Topic: Is c always the speed of light?
Replies: 88
Views: 544

Re: Is c always the speed of light?

Yes, c is a constant equal to 3*10^8 m/s, and it is commonly used in equations c=(lambda)(nu)...in other words, wavelength*frequency. Another side note: the speed of light is lower case c. Please do not confuse it with C as in Celsius or C as in carbon!
by Rachel Kho Disc 2G
Sun Nov 01, 2020 10:54 pm
Forum: Quantum Numbers and The H-Atom
Topic: Sapling #21
Replies: 4
Views: 69

Sapling #21

The question is: how many electrons in an atom can have these sets of quantum numbers?

I was able to get the answers, but I'm having trouble with understanding why there are 14 electrons if n=5 and l=3. Would someone be able to help me out? Thanks!
by Rachel Kho Disc 2G
Sun Nov 01, 2020 10:51 pm
Forum: DeBroglie Equation
Topic: Sapling #25
Replies: 4
Views: 64

Re: Sapling #25

For energy of a photon, use E=hv and c=v(lambda). Then for the energy of an electron, use E=1/2mv^2. Don't forget to convert micrometers to meters because I absolutely made that mistake a couple of times! (1 micrometer=1*10^-6m).
by Rachel Kho Disc 2G
Sun Nov 01, 2020 10:49 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Sapling #8 week2-4
Replies: 5
Views: 73

Re: Sapling #8 week2-4

To isolate lambda, you multiply both sides by lambda so that eventually you'll get lambda = 1/(1.0974*10^7 m/s)((1/nf^2)-(1/ni^2). From there, you should be getting the answer in meters which you can then convert to nanometers.
by Rachel Kho Disc 2G
Sun Nov 01, 2020 10:28 pm
Forum: Trends in The Periodic Table
Topic: sapling #23
Replies: 6
Views: 25

Re: sapling #23

I'm also having trouble with this, because I got the first part of the answer correct but I don't know what I'm doing wrong for the second part. When I ask for hints, it says that I need to use conversions of eV to 1.602*10^-22 kJ, and then also Avogadro's number. Then once you have that answer, you...
by Rachel Kho Disc 2G
Sun Nov 01, 2020 9:40 pm
Forum: Photoelectric Effect
Topic: Sapling Homework #6
Replies: 3
Views: 46

Sapling Homework #6

The question reads: When a metal was exposed to photons at a frequency of 1.45×1015 s−1, electrons were emitted with a maximum kinetic energy of 3.70×10−19 J. Calculate the work function, Φ, of this metal. What is the maximum number of electrons that could be ejected from this metal by a burst of ph...
by Rachel Kho Disc 2G
Sun Oct 25, 2020 9:10 pm
Forum: Molarity, Solutions, Dilutions
Topic: mmol
Replies: 14
Views: 228

Re: mmol

mmol means millimole. If you want to convert it to moles, just multiply the amount of mmol by 10^-3. Also, think of it this way: don't let the fact that the base unit is a mol. Just remember the King Henry Died By Drinking Chocolate Milk acronym and use it to multiply or divide by 10^n when necessa...
by Rachel Kho Disc 2G
Sun Oct 25, 2020 8:53 pm
Forum: *Shrodinger Equation
Topic: Hamiltonian
Replies: 3
Views: 51

Hamiltonian

Can anyone explain why the Hamiltonian is a double derivative? I remember learning and understanding it during lecture but as I'm looking back over my lecture notes I'm forgetting what was meant by that.
by Rachel Kho Disc 2G
Sun Oct 25, 2020 8:45 pm
Forum: Properties of Light
Topic: Midterm Conceptual Questions
Replies: 5
Views: 72

Midterm Conceptual Questions

Does anyone know any examples of possible concept questions that they'll ask on the midterm? Or does anyone have access to a worksheet of concept questions for practice? Thanks!
by Rachel Kho Disc 2G
Sun Oct 25, 2020 8:36 pm
Forum: Administrative Questions and Class Announcements
Topic: Step Up Sessions
Replies: 71
Views: 4678

Re: Step Up Sessions

Also are all UA peer-learning and TA office hours happening as usual for this week or are they cancelled because it is a midterm week?
by Rachel Kho Disc 2G
Sun Oct 25, 2020 8:28 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Advice for studying
Replies: 92
Views: 2204

Re: Advice for studying

Get as much practice in as possible! You can find extra problems in the textbook, sapling, UA peer-learning sessions, etc. If there is a difficult concept, you can go to office hours or even watch a video on YouTube.
by Rachel Kho Disc 2G
Sun Oct 18, 2020 8:40 pm
Forum: Properties of Light
Topic: Units to know
Replies: 4
Views: 50

Re: Units to know

You probably don't really need to memorize units, but it would probably be helpful to at least be quick with the units that Professor Lavelle gave us in lecture so that you save time when you're taking a test. From my notes, he gave us giga (10^9), mega (10^6), kilo (10^3), deci (10^-1), centi (10^-...
by Rachel Kho Disc 2G
Sun Oct 18, 2020 8:34 pm
Forum: Student Social/Study Group
Topic: Midterm
Replies: 7
Views: 29

Re: Midterm

I also find attending UA peer review sessions really effective. The undergraduate assistants are also students who have taken this course in the past so they're able to explain difficult concepts pretty well. The workshop sessions have worksheets of extra problems to go over so you get the practice ...
by Rachel Kho Disc 2G
Sun Oct 18, 2020 7:22 pm
Forum: Significant Figures
Topic: Sig Figs and Zeroes
Replies: 5
Views: 71

Sig Figs and Zeroes

I always have trouble with determining significant figures when zeroes are involved, either before or after the decimal place. Does anyone have any concise or definite rules about how to deal with zeroes in sig figs?
by Rachel Kho Disc 2G
Sun Oct 18, 2020 7:15 pm
Forum: Administrative Questions and Class Announcements
Topic: Respondus
Replies: 3
Views: 49

Re: Respondus

My TA sent a whole list of instructions, but basically: 1. You download the respondus. Maybe there's a site where you can do that but my TA had a url on his TA site. 2. Launch the lockdown browser. 3. On the pop-up, press open lockdown browser 4. There should be another pop-up, so press close applic...
by Rachel Kho Disc 2G
Sun Oct 18, 2020 6:58 pm
Forum: General Science Questions
Topic: External Webcam/Exam procedure
Replies: 4
Views: 38

Re: External Webcam/Exam procedure

If you don't want to buy an external webcam, my TA also mentioned there's a possibility that you could use another computer device if one is available to you! Maybe if you have a desktop computer at home, you can use that to proctor the exam and then use your laptop's webcam to record your workspace.
by Rachel Kho Disc 2G
Sun Oct 11, 2020 3:42 pm
Forum: Balancing Chemical Reactions
Topic: Balancing equations.
Replies: 35
Views: 820

Re: Balancing equations.

I also am confused about balancing equations that have polyatomic ions? For example I know this is supposed to be balanced already: 3 Pb(NO3)2 + 2 Na3PO4 --> Pb3(PO4)2 + 6 NaNO3 But I'm not sure how that can be when there aren't any parentheses around the second molecule in the reactants and the sec...
by Rachel Kho Disc 2G
Sun Oct 11, 2020 2:56 pm
Forum: Limiting Reactant Calculations
Topic: Question 10 homework
Replies: 9
Views: 155

Re: Question 10 homework

Hi, trying to understand how the strucure creates the molecular mass, I'm thinking each vertex represents one carbon plus an additional hydrogen if not already bonded to another distinct molecule? So using this information, could add the mass of carbon and hydrogen for each vertex since the carbons...
by Rachel Kho Disc 2G
Sun Oct 11, 2020 2:37 pm
Forum: Empirical & Molecular Formulas
Topic: Molecular Compound
Replies: 3
Views: 54

Re: Molecular Compound

My TA told me that's not necessary because the class is more about applying concepts and formulas, but I think it would be good to know the common polyatomic ions!
by Rachel Kho Disc 2G
Sun Oct 11, 2020 2:34 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Calculating Molar Mass (Sapling Week 1 #10)
Replies: 6
Views: 79

Re: Calculating Molar Mass (Sapling Week 1 #10)

Another good visualization tactic is to draw out the molecule! There is a carbon at each "kink" in the molecule, so for 2-butanone there are 4 carbon atoms. Each carbon atom has to have 4 bonds, and you can fulfill this quota by attaching hydrogen atoms which only require 1 bond to each ca...
by Rachel Kho Disc 2G
Sat Oct 10, 2020 7:39 pm
Forum: Limiting Reactant Calculations
Topic: Question 10 homework
Replies: 9
Views: 155

Re: Question 10 homework

For this question, do we need to know the chemical formula 2-butanone and 3-methyl-3-hexanol in order to solve this question? And if we did, would we just search up what the chemical formula is if we didn't know beforehand? You would only need to know the formula so that you could figure out the mo...

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