Search found 56 matches

by Grecia Velasco 4D
Sat Dec 07, 2019 9:47 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 5332

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

Naren_Ramesh_4D wrote:On question 2b of the mini marshmallow, does the order of the ligand in the coordination complex matter?


I don't think so BUT its good to go in order just in case :)
by Grecia Velasco 4D
Sat Dec 07, 2019 8:49 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 5332

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

Are we supposed to know how to hybridize lone pairs? Because during class, Lavelle said no but its in marshmallows so im not sure.
by Grecia Velasco 4D
Sat Dec 07, 2019 3:44 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 5332

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

ZevMarx-Kahn3C wrote:
Hannah Romano 4D wrote:when are the answers for marshmallows being posted???


I'd also love to know!


Fellas, i gotta feeling it's either gonna be really late at night or tomorrow morning. Fluoride ion (F-) in the chemistry community thread.
by Grecia Velasco 4D
Mon Dec 02, 2019 10:25 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: Hydrogen Bond Sites
Replies: 5
Views: 80

Re: Hydrogen Bond Sites

Hydrogen bonding occurs when there is a hydrogen bonded to a N,O, or F atom and is attracted to another N,O, or F atom or vise versa. So, the number of hydrogen bonding sites consists of the number or lone pairs on the N,O or F molecules (because they must essentially share electrons with the H ato...
by Grecia Velasco 4D
Mon Dec 02, 2019 10:21 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelating complexes
Replies: 6
Views: 98

Re: Chelating complexes

If something is a chelate what does that tell us and how would we identify it? Is there more to know other than just the definition of it? I think a good way to see if something is a chelate is to ask yourself "does this central atom have multiple polydentate ligands attached to it?" If t...
by Grecia Velasco 4D
Mon Dec 02, 2019 10:17 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: increasing pH and decreasing pH
Replies: 4
Views: 50

Re: increasing pH and decreasing pH

705081525 wrote:More protons means lower pH which means a stronger acid? Correct?


Strong acid= more hydronium ion = low pH
Weak acid= less hydronium ion = high pH

So like, low pH is more acidic and high pH is more basic.
by Grecia Velasco 4D
Mon Dec 02, 2019 10:12 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 9
Views: 109

Re: Coordination Number

It's the number of points at which ligands are attached to the central atom. Remember some ligands can connect to the central atom twice (polydentate) so it's not exactly the number of ligands. Do the bi/tri/polydentate is how many times a single ligand can bind to a central transitional metal? Tha...
by Grecia Velasco 4D
Mon Dec 02, 2019 10:11 pm
Forum: Administrative Questions and Class Announcements
Topic: Grades
Replies: 15
Views: 285

Re: Grades

Chanel D_4E wrote:Yes, you need at 250 in order to pass with a C-.


Thanks! I totally forgot about this until now.
by Grecia Velasco 4D
Mon Dec 02, 2019 10:10 pm
Forum: Calculating the pH of Salt Solutions
Topic: pKa vs Ka
Replies: 6
Views: 78

Re: pKa vs Ka

PKa= -Log[Ka] (for weak acids, log of Ka)

Ka= [A-][H+]/[AH] (acid dissociation constant)

Smalled Ka = larger PKa = weaker acid
by Grecia Velasco 4D
Tue Nov 26, 2019 9:57 am
Forum: Administrative Questions and Class Announcements
Topic: Final Exam Content
Replies: 14
Views: 242

Re: Final Exam Content

Yazmin Bocanegra 3L wrote:Is the final exam going to be everything from throughout the quarter, or is it going to be everything from the midterm and beyond?


it's all the material from the quarter
by Grecia Velasco 4D
Tue Nov 26, 2019 9:56 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Use of Bronsted or Lewis Definitions
Replies: 7
Views: 91

Re: Use of Bronsted or Lewis Definitions

Trent Yamamoto 4I wrote:In regards to our class, should we use the Bronsted definition or Lewis definition?


Lavelle said any of the two will do :)
by Grecia Velasco 4D
Tue Nov 26, 2019 9:56 am
Forum: Hybridization
Topic: How to write
Replies: 3
Views: 49

Re: How to write

If you count the number of valence electrons, you can determine the atoms hybridization. For example if you have a Carbon atom, which has 2 electrons in the 2s and 2 electrons in the 2p orbitals, then these orbitals would combine to form a hybridization of sp3. This means that now the Carbon atom c...
by Grecia Velasco 4D
Tue Nov 26, 2019 9:53 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Online Textbook
Replies: 6
Views: 97

Re: Online Textbook

Haley Dveirin 4B wrote:Is there a way to access the chemistry textbook online?


If you got the bundle from the UCLA store, you should have received a launchpad code for the online chem book.
by Grecia Velasco 4D
Mon Nov 25, 2019 3:23 pm
Forum: Air Pollution & Acid Rain
Topic: Clean Coal vs Dirty Coal?
Replies: 16
Views: 211

Re: Clean Coal vs Dirty Coal?

BeylemZ-4A wrote:can someone explain the difference between clean coal and dirty coal? I remember it being explained in the lecture in terms of Carbon of Sulfur dominant, but I don't remember which was clean and which was dirty.


Clean coal has lower sulfur content but both clean and dirty produce CO2.
by Grecia Velasco 4D
Wed Nov 20, 2019 4:15 pm
Forum: General Science Questions
Topic: Final
Replies: 10
Views: 206

Re: Final

905174774 wrote:Would the final be cumulative or will we be tested on everything after the midterm?


It's probably cumulative because the midterm was.
by Grecia Velasco 4D
Wed Nov 20, 2019 4:14 pm
Forum: Electronegativity
Topic: electronegativity of hydrogen
Replies: 3
Views: 120

Re: electronegativity of hydrogen

what is the electronegativity of hydrogen? like if a question asks which has greater ionic character (ie, more EN difference) between HCl and HI or between CH4 and CF4? similarly, where can you imagine hydrogen on the periodic table in terms of where it fits in trends? Hydrogen has low electronegat...
by Grecia Velasco 4D
Wed Nov 20, 2019 4:00 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands
Replies: 4
Views: 64

Re: Ligands

Ligands surround the central atom. It's just a name for bonded elements/molecules to central atom.
by Grecia Velasco 4D
Tue Nov 19, 2019 9:25 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Cylindrical Symmetry
Replies: 1
Views: 47

Re: Cylindrical Symmetry

I kind of think of it like sigma bonds are gears that help rotate atoms. Kind of like a corndog, you can rotate the corn dog on the stick because the stick allows it to rotate. Weird way to put it, I know, but studying does that to you.
by Grecia Velasco 4D
Tue Nov 19, 2019 9:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Can linear molecular shapes have lone pair?
Replies: 4
Views: 59

Can linear molecular shapes have lone pair?

It the bond angle is 180*, won't adding a lone pair decrease the 180* and make it non linear? Kind of confused that it says "may have lone pairs" in 2E.1 of homework. Thanks!
by Grecia Velasco 4D
Sun Nov 17, 2019 11:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Double and triple bonds
Replies: 4
Views: 67

Re: Double and triple bonds

Multiple bonds are still considered one region of electron density.
by Grecia Velasco 4D
Sun Nov 17, 2019 11:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: dipole moments
Replies: 11
Views: 111

Re: dipole moments

They're kind of like vectors and cancel when they face the opposite direction.
by Grecia Velasco 4D
Sun Nov 17, 2019 11:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 7
Views: 109

Re: Bond Angles

Lone pairs increase bond angles because they repulse electrons more than bonded pairs.
by Grecia Velasco 4D
Sun Nov 17, 2019 11:06 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Naming the Molecular Shapes
Replies: 7
Views: 148

Re: Naming the Molecular Shapes

Majority of names are based on geometric shapes but in the case of the few that aren't, you should rely on flashcards with examples of each.
by Grecia Velasco 4D
Sun Nov 17, 2019 11:04 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone vs. Bonding Pair
Replies: 6
Views: 98

Re: Lone vs. Bonding Pair

Lone pairs take up more space than bonded pairs.
by Grecia Velasco 4D
Mon Nov 04, 2019 9:30 pm
Forum: Octet Exceptions
Topic: Octet Rule exceptions
Replies: 14
Views: 333

Re: Octet Rule exceptions

Juliet Stephenson 4E wrote:Hydrogen, Helium, Lithium, and Beryllium are exceptions because they only have s orbitals. Elements that are period 3+ can also potentially expand their octet.


So any element besides the first 10 elements can have expanded octets?
by Grecia Velasco 4D
Mon Nov 04, 2019 9:21 pm
Forum: *Shrodinger Equation
Topic: Shrodinger equation
Replies: 7
Views: 278

Re: Shrodinger equation

Guzman_1J wrote:Is this going to be on the test? I don’t think we went over this one In detail.


I don't think we need to know the Schrodinger equation. He went over it super briefly and my TA hasn't mentioned it.
by Grecia Velasco 4D
Mon Nov 04, 2019 9:19 pm
Forum: Properties of Light
Topic: When do you use light equations?
Replies: 3
Views: 104

When do you use light equations?

Hey guys,
I'm confused as to when use light equations (c=wavelengthxfrequency, and E=hc/wavelength) because some questions provide wavelengths already and it's technically not speed of light being used. Thank you!
by Grecia Velasco 4D
Mon Nov 04, 2019 9:17 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s or 3d first?
Replies: 14
Views: 388

Re: 4s or 3d first?

You fill the 4s shell before the 3d shell. But, I believe Lavelle wants us to write 3d first since you remove electrons from 4s first. So we write 3d first regardless if 4s is filled in first? Does this rule apply to any other orbitals? Because my TA said to follow the order: 1s 2s 2p 3s 3p 3d 4s 4...
by Grecia Velasco 4D
Mon Nov 04, 2019 9:15 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s or 3d first?
Replies: 14
Views: 388

Re: 4s or 3d first?

Anna Chen 4L wrote:The 4s orbitals have a lower energy than the 3d orbitals, so the 4s orbitals are filled first. However, Lavelle has said to write 3d first.


Do you know if Cr and Cu are the exceptions to this rule because their 3d orbitals are filled first? Thank you!
by Grecia Velasco 4D
Wed Oct 30, 2019 4:57 pm
Forum: Ionic & Covalent Bonds
Topic: Midterm
Replies: 28
Views: 442

Re: Midterm

TanveerDhaliwal3G wrote:What content will the midterm be covering? Someone told me that the midterm goes up to the lecture of Friday 10/25 but I just wanted to clarify.


It's posted online! But for recap, fundamentals to end of Focus 2D.
by Grecia Velasco 4D
Wed Oct 30, 2019 4:56 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic Bonds
Replies: 6
Views: 64

Re: Ionic Bonds

Natalie Benitez 1C wrote:Just for clarification, ionic bonds are formed between elements that are further from each other due to a substantial difference in their electronegativity?


If the electronegativity difference is greater than 2 then it is a ionic bond.
by Grecia Velasco 4D
Wed Oct 30, 2019 4:55 pm
Forum: Ionic & Covalent Bonds
Topic: Format of midterm?
Replies: 12
Views: 168

Re: Format of midterm?

EmilyJoo_1G wrote:Does anyone know if the questions on the midterm will only have free-response questions like Test 1?


Seeing that it's only 8 questions, I'm 90% sure it will be multiple step free response.
by Grecia Velasco 4D
Wed Oct 30, 2019 4:55 pm
Forum: Ionic & Covalent Bonds
Topic: Octet Rule
Replies: 8
Views: 117

Re: Octet Rule

Mariah wrote:How do we know which elements have expanded octets? Do these need to be memorized?


Lavelle said that elements in row three have expanded octets.
by Grecia Velasco 4D
Wed Oct 30, 2019 4:52 pm
Forum: Ionic & Covalent Bonds
Topic: ionic vs covalent bonds
Replies: 6
Views: 90

Re: ionic vs covalent bonds

Jacob Puchalski 1G wrote:So basically, whether a bond is ionic or covalent depends on the difference of the electronegativities of the atoms involved?


Pretty much. If electronegativity difference is greater than 1.7 then its ionic but if it's less than 1.7 then it's covalent.
by Grecia Velasco 4D
Tue Oct 22, 2019 10:09 am
Forum: Properties of Light
Topic: Chemistry Community Posts
Replies: 10
Views: 344

Re: Chemistry Community Posts

Post at least a new set of 5 every week just in case.
by Grecia Velasco 4D
Tue Oct 22, 2019 10:08 am
Forum: Properties of Light
Topic: Homework due Next Week
Replies: 9
Views: 151

Re: Homework due Next Week

Any different 5 questions from "Quantum World".
by Grecia Velasco 4D
Tue Oct 22, 2019 10:06 am
Forum: Ionic & Covalent Bonds
Topic: Difference Between Ionic and Covalent
Replies: 8
Views: 474

Re: Difference Between Ionic and Covalent

Ionic bonds: noncovalent bonds (do not share electrons but transfer electrons), electronegativity difference: (X<0.5 is nonpolar; 0.5-1.7 is polar)

Covalent bonds: share electrons between two atoms, electronegativity difference: (X>1.7 is ionic)
by Grecia Velasco 4D
Tue Oct 22, 2019 9:58 am
Forum: Ionic & Covalent Bonds
Topic: Back and Fourth Arrows
Replies: 6
Views: 429

Re: Back and Fourth Arrows

Danieljm1B wrote:When are doubled headed arrows used in chemical formulas, or in other words, arrows pointing in both directions? Is it when a reaction is reversible? In that case when is it acceptable to use these arrows against using arrows just pointing one way?


Two arrows means reaction is reversible.
by Grecia Velasco 4D
Tue Oct 22, 2019 9:56 am
Forum: Ionic & Covalent Bonds
Topic: Week 4 Homework
Replies: 9
Views: 156

Re: Week 4 Homework

Cindy Adiwidjaja 1E wrote:For this week, are we supposed to do the homework based on the Quantum World, or based on the Ionic and Covalent Bonds?

I did 5 homework problems from each unit just in case but based on what everyone else is saying, focus on Quantum World.
by Grecia Velasco 4D
Wed Oct 16, 2019 10:45 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: #20 Post Module
Replies: 3
Views: 58

Re: #20 Post Module

Multiply KE with Avogadro's number.
by Grecia Velasco 4D
Wed Oct 16, 2019 10:42 am
Forum: Properties of Light
Topic: Question 1A.5
Replies: 4
Views: 77

Re: Question 1A.5

905416023 wrote:For this question, it says to list the types of photons of electromagnetic radiation in the order of increasing energy. Does this mean smallest to biggest?


It's from least to greatest energy.
by Grecia Velasco 4D
Wed Oct 16, 2019 10:41 am
Forum: *Shrodinger Equation
Topic: More Modules coming?...
Replies: 3
Views: 71

Re: More Modules coming?...

Does anyone know if Dr. Lavelle will be uploading any further modules on the rest of the Quantum Unit? I find them extremely helpful and would love to have more. I don't think so. He records his lectures but I don't think he'll be posting them anytime soon for our quarter. You can try youtube resou...
by Grecia Velasco 4D
Wed Oct 16, 2019 10:40 am
Forum: Properties of Light
Topic: Next test
Replies: 23
Views: 404

Re: Next test

ShreyaKannan1B wrote:Do we get all of the equations given to us on the next test?


Yeah, we'll get the majority of the equations but you'll have to derive some of your own (but you can do that with the original equation). Also, test 1 to midterm to test 2 to final is crazy.
by Grecia Velasco 4D
Wed Oct 16, 2019 10:37 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg equation [ENDORSED]
Replies: 73
Views: 3969

Re: Rydberg equation [ENDORSED]

Ruth Glauber 3L wrote:Where does the name Rydberg come from?


It's named after the Swedish scientist Johannes Rydberg.
by Grecia Velasco 4D
Wed Oct 09, 2019 12:28 pm
Forum: Empirical & Molecular Formulas
Topic: Test 1 Outline Question
Replies: 4
Views: 111

Re: Test 1 Outline Question

Just means know how to apply the N=n*Na and m=n*M formulas depending on what is being asked.
by Grecia Velasco 4D
Wed Oct 09, 2019 12:25 pm
Forum: Empirical & Molecular Formulas
Topic: Writing Empirical Formulas
Replies: 8
Views: 164

Re: Writing Empirical Formulas

Write the elements in the same order that the mass % composition is in. For example: H 25%, O 25%, C 25%, Fe 25% = HOCFe when solving for empirical formula.
by Grecia Velasco 4D
Wed Oct 09, 2019 12:22 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Molar Mass
Replies: 7
Views: 141

Re: Molar Mass

Molar mass = Grams/avogadro's constant, so just divide the grams of element given by 6.022x10^23 to find the molar mass.

n=m/Na
by Grecia Velasco 4D
Wed Oct 09, 2019 12:18 pm
Forum: Empirical & Molecular Formulas
Topic: Molecular formula
Replies: 6
Views: 799

Re: Molecular formula

First solve for empirical formula. Once you have that, calculate the empirical formula's molar mass. Because you have the molecular formula's molar mass, use the formula: molecular formula molar mass/ empirical formula molar mass=#. Use this # and multiple it with the empirical formula to get the mo...
by Grecia Velasco 4D
Wed Oct 09, 2019 12:15 pm
Forum: Empirical & Molecular Formulas
Topic: Molecular to Empirical Formula
Replies: 10
Views: 376

Re: Molecular to Empirical Formula

Calculate the empirical formula's molar mass. You should be given the molecular formulas molar mass. To find the molecular formula = Molecular formula molar mass/ empirical formula molar mass= #. Use this # and multiply it with the empirical formula, this gives you the molecular formula.
by Grecia Velasco 4D
Wed Oct 09, 2019 12:13 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Test 1 [ENDORSED]
Replies: 107
Views: 5289

Re: Test 1 [ENDORSED]

I took the test today and no, you only need your calculator and a pen. The periodic table will be provided and your test is printed. Good luck!
by Grecia Velasco 4D
Mon Sep 30, 2019 8:08 pm
Forum: Significant Figures
Topic: Rounding significant figures when it comes to elements of the periodic table
Replies: 6
Views: 95

Re: Rounding significant figures when it comes to elements of the periodic table

I've noticed that Dr. Lavelle uses his own periodic table (typically rounded to the second significant figure), so maybe go based off of that. When in doubt, round to the second significant figure (or at least thats what I do).
by Grecia Velasco 4D
Mon Sep 30, 2019 8:06 pm
Forum: Empirical & Molecular Formulas
Topic: 5 Homework Problems Due
Replies: 21
Views: 354

Re: 5 Homework Problems Due

I'm 95% sure you can do any 5 problems regardless of section (E,F,G). If you want to practice different skills, you should do problems from each section. If you feel like you need to work on one specific topic, like calculating mass percentages or molecular formulas, then you can focus on one sectio...
by Grecia Velasco 4D
Mon Sep 30, 2019 8:03 pm
Forum: Significant Figures
Topic: How to Write Out Final Answers
Replies: 5
Views: 84

Re: How to Write Out Final Answers

Dr. Lavelle said you can keep it in scientific notation for exams/notes. Just make sure that you convert it in labs because asking for an amount of reactant in scientific notation doesn't seem effective in a lab scenario.
by Grecia Velasco 4D
Mon Sep 30, 2019 8:01 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Reactions
Replies: 25
Views: 659

Re: Balancing Reactions

Chemical reactions must be balanced because of the Law of Conservation of Mass. Total Mass Before = Total Mass After Like Professor Lavelle stated, it's kind of like saying "4x=5x" in a math equation. If you don't balance a chemical reaction, then t's a false equation. You need to balance ...
by Grecia Velasco 4D
Mon Sep 30, 2019 7:55 pm
Forum: Empirical & Molecular Formulas
Topic: Formulas
Replies: 10
Views: 1324

Re: Formulas

In order to find the molecular formula, you need to follow these steps: calculate the mass percentage composition, find the empirical data, and then calculate the molecular formula. I'm going to assume you know all of these steps until the molecular formula step. In order to find find the number to ...
by Grecia Velasco 4D
Sun Sep 29, 2019 8:37 am
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student - Part II [ENDORSED]
Replies: 189
Views: 14363

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

Thank you for sharing your experience and journey! I really appreciate your advice. I'm not really sure what I want to do with my major (microbio/mimg), but the medical route seems like a viable (and interesting) option. I actually found myself relieved that even someone as accomplished as yourself ...

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