Search found 38 matches

by Hasmik Dis 2F
Sun Nov 22, 2020 11:50 pm
Forum: Hybridization
Topic: Sapling Week 7 & 8 HW Question 11
Replies: 3
Views: 28

Re: Sapling Week 7 & 8 HW Question 11

I know this may seem like an abstract tip : but think of it as “things.” How many things are around phosphorus ( the lone pair counting as “one thing”)? There’s 4. So then we can look at the hybridization answers. We ask ourselves, which answer is equivalent to 4? That would be s1p3- if you were to ...
by Hasmik Dis 2F
Sun Nov 22, 2020 11:46 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Replacing F with Cl in BF3 or Creating BF2Cl
Replies: 2
Views: 19

Re: Replacing F with Cl in BF3 or Creating BF2Cl

Although there is some repulsion, the whole point of the VESPR model is to make sure that we get the least repulsion possible. The two fluorine atoms coming closer together is the option to make this possible.
by Hasmik Dis 2F
Sun Nov 22, 2020 11:38 pm
Forum: Sigma & Pi Bonds
Topic: Delocalized pi Bonds
Replies: 2
Views: 8

Re: Delocalized pi Bonds

If electrons in a pi bond are confined to one region, it not as delocalized. On the other hand, whenever two orbitals overlap, the electrons can be free to spread over all atoms: this is delocalization!
by Hasmik Dis 2F
Sun Nov 22, 2020 11:34 pm
Forum: *Liquid Structure (Viscosity, Surface Tension, Liquid Crystals, Ionic Liquids)
Topic: determining viscosity
Replies: 6
Views: 47

Re: determining viscosity

Another tip with viscosity is to compare water and syrup ( I feel that real examples help more). Water of course flows more easily, but syrup has a thicker consistency so it doesn’t flow as smoothly. Syrup is thus more viscous.
by Hasmik Dis 2F
Sun Nov 22, 2020 11:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Axial vs Equatorial atoms
Replies: 2
Views: 8

Re: Axial vs Equatorial atoms

Basically a good rule of thumb is to remember that axial atoms that are connected to the rings at a 90 degree angle, while equatorial involves angles smaller than that.
by Hasmik Dis 2F
Sun Nov 15, 2020 5:48 pm
Forum: Ionic & Covalent Bonds
Topic: Sapling Q: Hydrogen Bonds
Replies: 7
Views: 27

Sapling Q: Hydrogen Bonds

So on #12 for the Sapling homework, it asked about hydrogen bonding. I know the two requirements needed for a hydrogen bond to occur: one site must have a highly electronegative atom with a lone pair (that being N, O , or F) and the other being a hydrogen atom bonded to another highly electronegativ...
by Hasmik Dis 2F
Sun Nov 15, 2020 5:06 pm
Forum: Lewis Acids & Bases
Topic: Sapling HW #6
Replies: 4
Views: 34

Re: Sapling HW #6

Hi Janna! So I think the issue is that B(OH)3 is under lewis base. I believe it is a lewis acid because as you can tell from the lewis structure, B can still accept electrons because it doesn't have a full octet (which is one of the Boron exceptions). Feel free to correct me if I'm wrong! I just tho...
by Hasmik Dis 2F
Sun Nov 15, 2020 1:51 am
Forum: Lewis Structures
Topic: textbook problem 2B #9
Replies: 4
Views: 33

Re: textbook problem 2B #9

I had a question for this problem too: did we have to know how to write out the compounds? Will the midterm test us on this? Also, will we have access to the electronegativity chart on the midterm?
by Hasmik Dis 2F
Sat Nov 14, 2020 3:56 pm
Forum: Lewis Structures
Topic: Outline 3 Sheet Question
Replies: 3
Views: 27

Outline 3 Sheet Question

The outline sheet on Dr Lavelle's website for Outline 3 said that we should be able to draw lewis structures of inorganic, organic, and biological compounds. I was wondering: what's the difference between these three? Also, It said we should be able to "Draw line structures of organic compounds...
by Hasmik Dis 2F
Sat Nov 14, 2020 3:52 pm
Forum: Bond Lengths & Energies
Topic: boiling point and IMS
Replies: 5
Views: 18

Re: boiling point and IMS

Dr Lavelle had a great explanation for this in one of his lectures. It is important to also note that some compounds may have higher boiling points than others due to the extent of polarability. For example, CH4 has a higher boiling point than CCL4. This is because since CCl4 has more electrons, it ...
by Hasmik Dis 2F
Sun Nov 08, 2020 2:52 am
Forum: Ionic & Covalent Bonds
Topic: energy released with the bonding of two ions
Replies: 2
Views: 16

Re: energy released with the bonding of two ions

Yea that value is just a given in the problem. I believe we're going to learn about lattice energy/change in energy during thermochemistry. But, as of right now, it's pretty much a given value. How they obtained it is a topic we're going to learn about later in chemistry.
by Hasmik Dis 2F
Sat Nov 07, 2020 12:08 pm
Forum: Resonance Structures
Topic: Oxidation Number
Replies: 9
Views: 43

Re: Oxidation Number

An oxidation number is basically the electron amount that an atom gains/loses whenever forming a bond with other atoms. There's usually set guidelines for assigning oxidation numbers. For example, group one is always +1, group 2 is +2, oxygen is always -2 (except for in hydrogen peroxide). There's m...
by Hasmik Dis 2F
Sat Nov 07, 2020 2:36 am
Forum: Student Social/Study Group
Topic: Unexpected Result of using Chemistry Communtiy
Replies: 7
Views: 54

Re: Unexpected Result of using Chemistry Communtiy

*cries in autofill*
Haha I actually kind of have my UCLA ID memorized, but not entirely. Only the first 6 numbers XD
Will definitely work on that!
by Hasmik Dis 2F
Sat Nov 07, 2020 2:24 am
Forum: Electronegativity
Topic: Fluorine
Replies: 7
Views: 39

Re: Fluorine

^ Flourine's small size does have associations with its electronegativity. Since the atom is extremely close to fulfilling its octet, the nucleus is going to tightly hold onto the electrons. This is why it also has a relatively smaller radius than the other atoms in the same group (the nuclear charg...
by Hasmik Dis 2F
Sat Nov 07, 2020 2:10 am
Forum: Coordinate Covalent Bonds
Topic: H20 Example from Lecture today
Replies: 4
Views: 33

Re: H20 Example from Lecture today

A good way to think about coordinate covalent bonding would be the BF3 example in Dr. Lavelle's lecture. In BF3, the B has a lower octet (6 valence electrons). Thus, it had room to bond with a F- (which could provide BF3 with the last two electrons to fill the octet). The BF3 then covalently bonds w...
by Hasmik Dis 2F
Sat Nov 07, 2020 2:00 am
Forum: Ionic & Covalent Bonds
Topic: Coulomb's PE
Replies: 3
Views: 16

Re: Coulomb's PE

In the lecture, he only introduced us to the formula and what each aspect of it meant. So, I believe as long as you understand the formula conceptually you will be fine. Otherwise, if he really expected us to know how to solve a problem using that formula, then he probably would have done some pract...
by Hasmik Dis 2F
Mon Nov 02, 2020 3:25 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem 14B Enrollment
Replies: 27
Views: 229

Re: Chem 14B Enrollment

It depends on what classes you're taking. I know Chem 14BL fills up fast, so if you wanted to take that with Chem 14B then I'd sign up for both first pass b/c 14B is a co-requisite for 14BL. I need to take LS30B though and that fills up faster so I'm using my first pass on it, but I'm not sure if I...
by Hasmik Dis 2F
Sun Nov 01, 2020 9:26 pm
Forum: Trends in The Periodic Table
Topic: Atomic vs Ionic Radius
Replies: 3
Views: 24

Re: Atomic vs Ionic Radius

Also, I wanted to add to Eva's answer the fact that Na+ has a stronger positive nuclear charge than Na. Therefore, that stronger pull the nucleus has on the electrons can account for the smaller radius.
by Hasmik Dis 2F
Sun Nov 01, 2020 9:24 pm
Forum: General Science Questions
Topic: Enrolling in Chem 14B and BL simultaneously?
Replies: 10
Views: 82

Re: Enrolling in Chem 14B and BL simultaneously?

I am also in the same dilemma. However, when I remember that lab is going to be online, I kinda want to wait until when it is safe to do the course in person. I've always loved labs in chemistry, so I would love to be able to do physical ones again!
by Hasmik Dis 2F
Sun Nov 01, 2020 9:20 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Sapling Question Number 20
Replies: 4
Views: 33

Re: Sapling Question Number 20

For stable configuration, it's basically when valence electrons are full and thus the atom is stable. For electron repulsion: when comparing the radius of two atoms, the one with more electrons will have the largest radius because of electron-electron repulsion. Hope that answered your last question...
by Hasmik Dis 2F
Sat Oct 31, 2020 1:05 am
Forum: DeBroglie Equation
Topic: Finding the mass of a molecule
Replies: 6
Views: 68

Re: Finding the mass of a molecule

I think your confusion is in the "amu" which just means "atomic mass units." That number just means mass also, so whenever you see "2.014 amu" it is essentially 2.014 grams. There's no actual conversion from amu to grams.
by Hasmik Dis 2F
Sat Oct 31, 2020 12:56 am
Forum: Properties of Electrons
Topic: Constructive vs Destructive
Replies: 6
Views: 39

Re: Constructive vs Destructive

I struggle with this too. My question is what overarching topic is this concept relevant to?
by Hasmik Dis 2F
Sun Oct 25, 2020 11:01 pm
Forum: Properties of Electrons
Topic: Kinetic energy for electrons
Replies: 3
Views: 23

Re: Kinetic energy for electrons

A key thing to look out for is if the question asks for the "maximum amount of electrons ejected." This was a sapling problem. If it asks to find the maximum then you know that Kinetic energy is zero because there's no excess energy.
by Hasmik Dis 2F
Sun Oct 25, 2020 3:26 pm
Forum: DeBroglie Equation
Topic: 1B.21 Conversion Question
Replies: 3
Views: 38

1B.21 Conversion Question

A baseball must weigh between 5.00 and 5.25 ounces (1 ounce= 28.3g). What is the wavelength of a 5.15-ounce baseball thrown at 92mph?

How would we have known the conversion from miles to meters if we were to have this question on a test?
by Hasmik Dis 2F
Sun Oct 25, 2020 1:52 pm
Forum: DeBroglie Equation
Topic: Textbook Question 1B.15
Replies: 6
Views: 59

Re: Textbook Question 1B.15

I've been having trouble with this problem too, but with part (A). I know we have to use DeBroglie's equation for wavelength, but I got 2.02x10^-7m, while the textbook's answer is 2.02x10^-10m. Did anyone else have the same problem? I can't seem to pinpoint where I went wrong.
by Hasmik Dis 2F
Sun Oct 25, 2020 2:42 am
Forum: DeBroglie Equation
Topic: Textbook Q 1B.19
Replies: 2
Views: 32

Textbook Q 1B.19

Question 1B.19 : Protons and neutrons have nearly the same mass. How different are their wavelengths? Calculate the wavelength of each particle when traveling at 2.75×10^5m•s^−1 in a particle accelerator and report the difference as a percentage of the wavelength of the neutron. I get that the wavel...
by Hasmik Dis 2F
Fri Oct 23, 2020 6:23 pm
Forum: Administrative Questions and Class Announcements
Topic: Step Up Sessions
Replies: 71
Views: 4352

Re: Step Up Sessions

MIDTERM REVIEW SESSIONS - I saw on the class website that there is a tab for midterm review sessions. I was wondering if they are apart of step up sessions or if they are hosted by Dr. Lavelle at a different time/location. And, when will the review session be? So Dr Lavelle and the TAs aren’t neces...
by Hasmik Dis 2F
Wed Oct 21, 2020 5:27 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation
Replies: 11
Views: 90

Re: Rydberg Equation

I know this was explained many times but for some reason, it's just not clicking. Can anyone explain again why the equation En=-hR/n^2 is negative?
by Hasmik Dis 2F
Sun Oct 18, 2020 4:30 pm
Forum: Properties of Light
Topic: Conversion Factor - m to nm
Replies: 6
Views: 37

Conversion Factor - m to nm

How do we convert meters to nanometers?
by Hasmik Dis 2F
Fri Oct 16, 2020 12:22 am
Forum: General Science Questions
Topic: Polyatomic Ions
Replies: 6
Views: 43

Polyatomic Ions

Does anyone know if we have to memorize all the polyatomic ions? I've done a few homework problems where it asked for carbonate, for example, but it didn't give the formula.
by Hasmik Dis 2F
Wed Oct 14, 2020 10:08 pm
Forum: Photoelectric Effect
Topic: Exercise 1B.3
Replies: 2
Views: 38

Re: Exercise 1B.3

One way you could've tackled the question is by eliminating the answers that were obviously wrong. Black-body radiation is not even a chemistry-relevant topic. Electron diffraction refers to the wave-like properties- which was the conception people had of electromagnetic radiation before the emergen...
by Hasmik Dis 2F
Wed Oct 14, 2020 2:53 pm
Forum: Properties of Light
Topic: Memorization of Increasing Energy
Replies: 4
Views: 54

Re: Memorization of Increasing Energy

I was in the same step-up session that spoke about this. The UA said that we should at least have an idea of the order! She gave a good mnemonic for memorization: Rabbits - radio waves Mate - microwaves In - infrared Very - visible light (400-700nm) Unusually - UV Expensive - x-rays Gardens - gamma ...
by Hasmik Dis 2F
Tue Oct 13, 2020 3:08 pm
Forum: Properties of Light
Topic: Memorizing Wavelengths
Replies: 10
Views: 59

Re: Memorizing Wavelengths

I'm currently in a step-up session and she said we should be familiar with the order of the different electromagnetic waves for exams. A good mnemonic she mentioned was: Rabbits Mate In Very Expensive Gardens (in order of increasing frequency).
by Hasmik Dis 2F
Sat Oct 10, 2020 3:39 pm
Forum: Administrative Questions and Class Announcements
Topic: Respondus
Replies: 8
Views: 97

Re: Respondus

Is Respondus going to be used for quizzes or..? Are we going to have a quiz next week/every week? Anyone have any idea? Still trying to adjust to the format of this class.
Thanks!
by Hasmik Dis 2F
Fri Oct 09, 2020 3:38 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem 14A Website Problem
Replies: 1
Views: 22

Chem 14A Website Problem

So lately I've been having trouble logging into Dr. Lavelle's website out of a sudden. For some reason whatever password I put is incorrect, which is strange because it's the same password I've been using. Has anyone else had this problem? Does anyone know what I can do? I really need access to that...
by Hasmik Dis 2F
Fri Oct 09, 2020 12:05 am
Forum: Balancing Chemical Reactions
Topic: How moles should be balanced on each side
Replies: 11
Views: 61

Re: How moles should be balanced on each side

One tip I remember from my AP chemsitry class is to always leave the oxygen until the last step. Anytime you'll have a combustion reaction where you're dealing with 02 and H2O, the best thing to do is to leave those alone and focus on balancing the other elements first. Once you get the other elemen...
by Hasmik Dis 2F
Wed Oct 07, 2020 9:41 pm
Forum: Administrative Questions and Class Announcements
Topic: Step Up Sessions
Replies: 71
Views: 4352

Re: Step Up Sessions

Did anyone attend the 6-8pm workshop today? Can someone give an overview of what was discussed during that session. I was planning on attending but something came up.
by Hasmik Dis 2F
Wed Oct 07, 2020 7:22 pm
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student - Part II [ENDORSED]
Replies: 188
Views: 13852

Re: Advice from a Medical Student - Part II [ENDORSED]

Hello! Thank you for sharing your story with the rest of us! I am currently a freshman and a MCDB major and I am also interested in pursuing a career in the medical field. I wanted to ask: do you have any study tips for this class? I do know one importnat thing to do is practice problems, however, w...

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