Search found 60 matches

Wed Jan 13, 2021 10:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Dilute Solution
Replies: 4
Views: 15

Re: Dilute Solution

For our purposes, I believe any dilution problem the dilutant is just water.
Wed Jan 13, 2021 10:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pH and pKa
Replies: 6
Views: 26

Re: pH and pKa

It just depends on what the question is asking. If it asks for equilibrium or a constant, use pKa. If it asks for a concentration or anything related to concentration use pH.
Wed Jan 13, 2021 9:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kb and Ka
Replies: 2
Views: 15

Kb and Ka

Do we have to know the Kb and Ka of certain weak bases and acids or will we have a sheet with a list of them?
Wed Jan 13, 2021 8:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework problem 6B.9
Replies: 3
Views: 19

Homework problem 6B.9

For the pH of row (i) in the problem, how did they get 0.176? In general, how do you find the pH of concentrations over 1?
Mon Jan 11, 2021 1:39 pm
Forum: Administrative Questions and Class Announcements
Topic: Acids and Bases Section for Chem 14B
Replies: 2
Views: 35

Acids and Bases Section for Chem 14B

Is there a place to post questions for acids and bases for chem 14b? I'm not sure if I just missed the section, but I can't seem to find it under chemical equilibrium.
Thu Jan 07, 2021 7:31 pm
Forum: Ideal Gases
Topic: Kc vs Kp
Replies: 106
Views: 881

Re: Kc vs Kp

If the problem gives partial pressures of reactants or products or it asks for the partial pressures, use Kp. Otherwise use Kc. Also in lecture, Lavelle talks about the way to get the conc of a gas from knowing its partial pressure. So if need be you could do that.
Thu Jan 07, 2021 7:27 pm
Forum: Administrative Questions and Class Announcements
Topic: Sapling Assignments
Replies: 26
Views: 108

Re: Sapling Assignments

Sapling is your graded homework assignment and mandatory. If you check the sapling website, it will say what week it is due. It's always due on sunday.
Thu Jan 07, 2021 7:23 pm
Forum: Administrative Questions and Class Announcements
Topic: Lecture Format
Replies: 22
Views: 103

Re: Lecture Format

The lectures are recorded and get released under the media tab in CCLE at the time of your class. There are also discussions which he calls lectures that are basically office hours for homework questions. Those are live on zoom.
Thu Jan 07, 2021 7:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Gas Constant (R)
Replies: 12
Views: 44

Re: Gas Constant (R)

R is 8.314 J*K^-1*mol^-1. I think the only time you would need to convert it is if the units are kJ which then R would be 8.314 kJ*K^-1*mol^-1
Thu Jan 07, 2021 7:17 pm
Forum: Student Social/Study Group
Topic: Advice for someone who didn't take 14A with professor Lavelle
Replies: 59
Views: 199

Re: Advice for someone who didn't take 14A with professor Lavelle

I'd say to do well on exams just do a lot of practice problems. As people mentioned above, UA worksheets are really helpful. And additionally, the homework problems on the outlines are good practice. The problems on sapling are relatively easy and only scratch the surface of the difficulty of proble...
Wed Dec 09, 2020 11:11 am
Forum: Student Social/Study Group
Topic: Study Group
Replies: 2
Views: 39

Re: Study Group

lavelle@chem.ucla.edu: this is his email. You can find it if you google his name. it's on his webpage in the chemistry department
Wed Dec 09, 2020 11:06 am
Forum: Calculating the pH of Salt Solutions
Topic: Telling if a Solution is Basic or Acidic?
Replies: 5
Views: 56

Re: Telling if a Solution is Basic or Acidic?

If you remember from lecture 28, Lavelle said that while elements like Na and Cl have a charge, they have very little impact on the acidic or basic qualities. So starting with the first equation, the product of the titration is NaCl. Both Na and Cl have no impact on the pH level of the solution so ...
Wed Dec 09, 2020 10:59 am
Forum: Calculating the pH of Salt Solutions
Topic: Telling if a Solution is Basic or Acidic?
Replies: 5
Views: 56

Re: Telling if a Solution is Basic or Acidic?

If you remember from lecture 28, Lavelle said that while elements like Na and Cl have a charge, they have very little impact on the acidic or basic qualities. So starting with the first equation, the product of the titration is NaCl. Both Na and Cl have no impact on the pH level of the solution so i...
Wed Dec 09, 2020 10:52 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation
Replies: 2
Views: 24

Re: Rydberg Equation

I think for the lecture we will only have the frequency equation for Rydberg's equation. So if we need to find the energy level of n, or the change in energy level, we can just use the equation that relates energy to frequency: E=hv.
Wed Dec 09, 2020 10:49 am
Forum: Student Social/Study Group
Topic: lecture bruincast #29 problem
Replies: 10
Views: 73

Re: lecture bruincast #29 problem

For the first 20 minutes, the lecture was playing just fine, but now it also says video file cannot be played... I'm not sure if it's my wifi or me...
Wed Dec 02, 2020 6:32 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9C.3 a
Replies: 2
Views: 13

Re: 9C.3 a

potassium hexacyanidochromate(III): if we break down the name, we know that the molecules/atoms in the compound are potassium (K), cyanide (CN-), and chromate (Cr). Since potassium is not in the same word as chromate, it is outside of the coordination sphere so we have that outside the brackets - K....
Wed Dec 02, 2020 6:28 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9C.3 d
Replies: 1
Views: 15

Re: 9C.3 d

Even though there is no di, tri, etc in front of oxalato, we still have to use bis because oxalato is polydentate. If you look at the diagram for oxalato in the book, you can see where the multiple bonding sites are.
Wed Dec 02, 2020 10:55 am
Forum: Student Social/Study Group
Topic: How are you?
Replies: 111
Views: 697

Re: How are you?

Feeling slightly overwhelmed after realizing that all my finals are bunched up on the weekend of week 10 and first few days of finals week. But I'm working through my stress and I know that I can manage this!
Wed Dec 02, 2020 10:54 am
Forum: Bronsted Acids & Bases
Topic: HCl vs. HBr
Replies: 6
Views: 45

Re: HCl vs. HBr

Due to it's longer bond length, HBr can completely ionize more easily than HCl, meaning HBr can produce more H+ ions than HCl. Since acid strength is based on the number of protons produce, HBr is stronger than HCl.
Wed Dec 02, 2020 10:51 am
Forum: Bronsted Acids & Bases
Topic: Bronsted Acids/Bases vs Lewis
Replies: 2
Views: 23

Re: Bronsted Acids/Bases vs Lewis

It is possible for a substance to be a lewis acid and not a bronsted acid. Some acidic reactions don't involve protons, which is what the bronsted acid definition is based on, but all reactions involve electrons, which is what the lewis acid definition is based on.
Tue Nov 24, 2020 6:33 pm
Forum: Administrative Questions and Class Announcements
Replies: 4
Views: 41

Does an A+ versus an A make a difference on our GPA?
Tue Nov 24, 2020 6:33 pm
Forum: Hybridization
Topic: Finding Hybridization
Replies: 6
Views: 26

Re: Finding Hybridization

I think in the most recent lecture, Lavelle said that the number of bonding areas is the number of covalent bonds and these determine the hybridization. I am not sure if he mentioned any exceptions.
Tue Nov 24, 2020 6:15 pm
Forum: Administrative Questions and Class Announcements
Topic: Lectures Thanksgiving week
Replies: 8
Views: 72

Re: Lectures Thanksgiving week

In the email he just sent, he said that the last class this week is Wednesday and there is nothing Thursday or Friday. However, there will be UA and step-up sessions Saturday and sunday.
Tue Nov 24, 2020 6:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: carbon hydrogen bonds
Replies: 6
Views: 36

Re: carbon hydrogen bonds

No, they would not have an effect on the bond angles because the electron densities of the lone pairs on the outer four atoms don't interfere with any electron densities on the carbon.
Tue Nov 24, 2020 6:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 8 Participation Points
Replies: 6
Views: 58

Week 8 Participation Points

Since this week is shorter, do we still have to do 5 posts for participation or is the number changed?
Tue Nov 17, 2020 10:25 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Outer electrons for Elements with s and d shells
Replies: 1
Views: 23

Outer electrons for Elements with s and d shells

When counting the outer electrons for elements with s and d shells, do we count the electrons in the d shell as well? For example with Cobalt, would the number of valence electrons be 10 because we count both 4s2 and 3d8 or is it just 2 valence electrons?
Tue Nov 17, 2020 3:19 pm
Forum: Ionic & Covalent Bonds
Topic: Textbook 2D.3
Replies: 2
Views: 19

Re: Textbook 2D.3

The ionic or covalent characteristics of a bond are defined by the electronegativity difference between the atoms. The greater the difference the more ionic characteristics the bonds will have. Since Br is kept the same for each of these molecules, we just need to look at the electronegativity diffe...
Tue Nov 17, 2020 3:08 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2A.19 Exercise
Replies: 2
Views: 19

Re: 2A.19 Exercise

Even though the 3d shell has a higher energy level than the 4s shell, when removing electrons we still remove the 4s electrons first because they are in the outermost shell. Therefore with Ni who's configuration is usually [Ar]4s23d8, we remove the 4s2 to get Ni +2 ([Ar]3d8). The same goes for Sn 4+.
Tue Nov 17, 2020 3:01 pm
Forum: Lewis Structures
Topic: 2c #11
Replies: 2
Views: 13

Re: 2c #11

For exercise 11, to draw the lewis structures, you would just take the same steps as you do for any other inorganic lewis structure. The problem already states that Xe should be in the center of the molecule, so you know that the surrounding molecules will connect to Xe. Total up the number of valen...
Tue Nov 17, 2020 2:54 pm
Forum: Student Social/Study Group
Topic: Midterm Studying
Replies: 3
Views: 50

Re: Midterm Studying

Yup. Anything that we've covered after MT1 is material that could be on the midterm. I would make sure to know how to do everything stated in outline 3 and everything past the point "Understand the relationship between Schrodinger's equation, wave functions, and orbitals" in outline 2.
Tue Nov 17, 2020 2:50 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem 14B Lectures
Replies: 15
Views: 138

Re: Chem 14B Lectures

I assume that they'd be asynchronous just like they are now because Lavelle will be teaching about 900 students again.
Tue Nov 10, 2020 8:14 pm
Forum: Electronegativity
Topic: Electronegativity values
Replies: 4
Views: 17

Re: Electronegativity values

Massimo_Capozza_1H wrote:Should we remeber these values, or will we be given what they correspond to?

I think we should know the general trends, like the largest EN differences will result in ionic and the smaller EN differences will result in nonpolar covalent bonds.
Tue Nov 10, 2020 8:06 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm 2 Questions
Replies: 16
Views: 121

Re: Midterm 2 Questions

Massimo_Capozza_1H wrote:Will we be provided any more helpful sheets like the equation sheet and periodic table?

I think the equation sheet and periodic table are the same as the one from midterm 1.
Tue Nov 10, 2020 8:05 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm 2 Questions
Replies: 16
Views: 121

Re: Midterm 2 Questions

In Lavelle's email, he wrote that midterm 2 would be shorter because there has been less material covered. Midterm 2 will only cover any new material learned not covered in midterm 1.
Tue Nov 10, 2020 8:01 pm
Forum: Student Social/Study Group
Topic: Test Anxiety
Replies: 62
Views: 307

Re: Test Anxiety

I am not sure if anyone struggles with test anxiety... if you do, what are some techniques you guys use to deal with and control test anxiety? Thank you. I know our first midterm is done, but I think a good thing to do if you feel like you are breathing weirdly is to drink water during the test. Dr...
Tue Nov 10, 2020 8:00 pm
Forum: Student Social/Study Group
Topic: Exercising Our Minds and Bodies
Replies: 92
Views: 456

Re: Exercising Our Minds and Bodies

Hannah_Kim_1I wrote:Lavelle has mentioned the importance of exercising our mind and body so I was interested to see what types of exercises everyone was up to! I usually just go for walks/runs with my dog.

Aww that's so cute! I usually go on walks in target and get my steps in my circling all the isles.
Wed Nov 04, 2020 5:41 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic Bonding Question
Replies: 6
Views: 58

Re: Ionic Bonding Question

Yeah, that's right. The nonmetals on the rightmost side of the periodic table are more likely to lose electrons while the metals on the left side are more likely to gain electrons. Thus, when the nonmetals and metals make a compound, they will have a complete electron transfer to make an ionic bond.
Wed Nov 04, 2020 5:36 pm
Forum: Ionic & Covalent Bonds
Topic: Coordinate Covalent Bond
Replies: 3
Views: 18

Re: Coordinate Covalent Bond

A coordinate covalent bond is a type of covalent bond where both electrons in the bond come from one of the electrons. In the example, Lavelle gave with bromine, when bromine forms a coordinate covalent bond, the atom it forms the bond with is the one to donate both electrons.
Wed Nov 04, 2020 4:59 pm
Forum: Student Social/Study Group
Topic: Favorite TV shows
Replies: 176
Views: 818

Re: Favorite TV shows

Sara_Lim_3K wrote: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)

omg danny phantom though!! Lowkey, highkey my childhood crush.
Wed Nov 04, 2020 4:43 pm
Forum: Ionic & Covalent Bonds
Topic: Textbook Problem 2A.1
Replies: 4
Views: 25

Re: Textbook Problem 2A.1

For Mn, even though the d-orbitals have lower energy than the s and p orbitals, they are still counted when counting valence electrons.
Wed Nov 04, 2020 4:39 pm
Forum: Lewis Structures
Topic: Valence Electrons
Replies: 10
Views: 67

Re: Valence Electrons

You can find the number of valence electrons of an atom by looking at the periodic table. The column or groups of atoms determine the number of valence electrons they have. For example, group 1 (H, Li, etc.) has 1 valence electron while group 17 (F, Cl, etc.) has 7 valence electrons.
Tue Oct 27, 2020 7:43 pm
Forum: Administrative Questions and Class Announcements
Replies: 7
Views: 74

Does anyone know if there are answers to the UA worksheets?
Tue Oct 27, 2020 7:03 pm
Forum: Photoelectric Effect
Topic: vacuum
Replies: 3
Views: 44

Re: vacuum

It has to be done in a vacuum because, at normal atmospheric pressure, electrons bounce and collide with each other which would ruin the experiment. Without a vacuum the electrons could also crash into other molecules in the air like water vapor.
Mon Oct 26, 2020 2:10 pm
Forum: Administrative Questions and Class Announcements
Topic: Equation Sheet for Midterm
Replies: 1
Views: 28

Equation Sheet for Midterm

Does anyone know when the Equation and Constants sheet for the midterm will be posted and where we can find it?
Fri Oct 23, 2020 9:31 pm
Forum: General Science Questions
Topic: Practice problems for midterm
Replies: 3
Views: 40

Practice problems for midterm

Does anyone know where to find or get extra practice problems to study for the midterm? Will Lavelle provide us with any?
Fri Oct 23, 2020 9:28 pm
Forum: Properties of Electrons
Topic: Sapling Homework Week 2 question 8
Replies: 3
Views: 49

Re: Sapling Homework Week 2 question 8

The question wants you to use the Rydberg equation to solve for the two values of n (a principal quantum number for the electron), so you should start by looking at that equation.
Tue Oct 20, 2020 10:29 pm
Forum: Properties of Light
Topic: Speed of light
Replies: 25
Views: 158

Re: Speed of light

For tests, Lavelle said that for constants, he will give you the exact value he wants you to use so there will be no discrepancies between students.
Tue Oct 20, 2020 10:27 pm
Forum: DeBroglie Equation
Topic: At What Point does wavelength become undetectable?
Replies: 8
Views: 75

Re: At What Point does wavelength become undetectable?

Anything shorter than 10^-15 m is undetectable. I think in the lecture, Lavelle said that if you are asked a problem like this and the object you are given is significantly bigger than a molecule (like a baseball, book, or car), you can safely assume that that object follows classical mechanics and ...
Tue Oct 20, 2020 10:24 pm
Forum: Properties of Light
Topic: Sapling #10
Replies: 8
Views: 159

Re: Sapling #10

The mass of a single fluorine molecule is what is listed on the periodic table of elements. Since it is diatomic, you should double the amu. To get the correct wavelength, you have to convert the g/molecule into kg/molecule. Then using, wavelenth=h/(mv), the kg in the m will cancel with the kg in pl...
Sun Oct 18, 2020 8:01 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 1D Problem #11
Replies: 1
Views: 34

1D Problem #11

Problem: How many orbitals are in subshells with l equal to (a) 0; (b) 2; (c) 1; (d) 3? So, for (b), I got 9 because I added all the orbitals for l=0, l=1, and l=2, but the answer is 5. Why would you not add all the orbitals for each previous number of l because they could also be associated with th...
Fri Oct 16, 2020 10:15 am
Forum: Administrative Questions and Class Announcements
Topic: Quantum world syllabus problems
Replies: 4
Views: 42

Re: Quantum world syllabus problems

I think that the extra problems also cover week 2 and 3 since each section sort of corresponds to each new lecture.
Thu Oct 15, 2020 3:32 pm
Topic: Sapling Wk 2+3 #7
Replies: 3
Views: 70

Sapling Wk 2+3 #7

For question 7, it asks about temperature and wavelength. Does this mean we have to use wein's equation which is mentioned in the textbook or is there some other way to do the problem?
Thu Oct 15, 2020 3:30 pm
Forum: Photoelectric Effect
Topic: 1B #7
Replies: 4
Views: 41

Re: 1B #7

For part b, I first started by converting the 5.00 mg of Na to photons of Na. I converted 5.00 mg Na to moles of Na then to photons (there are 6.022 x 10^23 photons in a mol). Then I used the energy per photon I got in (a) multiplied by the number of photons I got to get the total energy emitted by ...
Thu Oct 15, 2020 3:30 pm
Forum: Photoelectric Effect
Topic: 1B #7
Replies: 4
Views: 41

Re: 1B #7

For part b, you have to first start by converting the 5.00 mg of Na to photons of Na. I converted 5.00 mg Na to moles of Na then to photons (there are 6.022 x 10^23 photons in a mol). Then I used the energy per photon I got in (a) multiplied by the number of photons I got to get the total energy emi...
Tue Oct 13, 2020 9:23 pm
Forum: Administrative Questions and Class Announcements
Topic: wavelengths for light
Replies: 9
Views: 93

Re: wavelengths for light

Just like the answer above, I think we would need to know, at the least, the range of visible light and the order in which all the types of electromagnetic light fall in terms of energy and wavelength. For example, from greatest to smallest in terms of energy would be Gamma, X-ray UV... etc. And fro...
Fri Oct 09, 2020 12:01 am
Forum: Balancing Chemical Reactions
Topic: Naming compounds
Replies: 21
Views: 190

Re: Naming compounds

I think for now the compounds will be given to us, but it's always good to start memorizing the ones that come up most often.
Thu Oct 08, 2020 12:12 pm
Forum: Balancing Chemical Reactions
Topic: States of Matter in Chemical Equations
Replies: 13
Views: 88

States of Matter in Chemical Equations

Should we be writing the states of matter of products and reactants when we are balancing chemical equations? For example, if we were writing the equation for the chemical reaction of aluminium and iron oxide, would we write Al(s) +Fe2O3(s) -> Al2O3 (s) + Fe(l) or do we write Al +Fe2O3 -> Al2O3 + Fe?
Wed Oct 07, 2020 10:45 am
Forum: Significant Figures
Topic: How man Sig Figs to use in the Textbook Problems
Replies: 7
Views: 80

How man Sig Figs to use in the Textbook Problems

I'm sorry if someone asked this already, but I was wondering how many sig figs to use when doing the textbook problems. I noticed the textbook donesn't specify for each problem, but the answers always vary in the number of sig figs they use.
Tue Oct 06, 2020 12:13 pm
Forum: Student Social/Study Group
Topic: Textbook Readings on Fundamental Topics
Replies: 5
Views: 56

Re: Textbook Readings on Fundamental Topics

My TA said that Lavelle draws a lot of his test questions from homework problems, so I assume that we won't be tested on the information we don't learn or isn't covered by the homework
Fri Oct 02, 2020 9:25 am
Forum: General Science Questions
Topic: Lecture Over Zoom
Replies: 12
Views: 352

Re: Lecture Over Zoom

For our first lecture at least, it's pre-recorded. You can find it underneath the media tab on CCLE.