Search found 63 matches

by serenabirkhoff_1K
Sat Dec 07, 2019 11:44 am
Forum: Photoelectric Effect
Topic: Module Question
Replies: 1
Views: 115

Module Question

Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. Given this info the part b asks How much energy is required to remove an electron from one sodium atom? If it helps the previous question asked What is the ...
by serenabirkhoff_1K
Fri Dec 06, 2019 3:32 pm
Forum: Hybridization
Topic: hybridization of lone pairs
Replies: 4
Views: 50

Re: hybridization of lone pairs

Ok so for lone pairs, do we just look at the regions of electron density and determine they hybridization for just that atom? For example, if I was given a N with 3 regions of electron density (one region being composed of a lone pair), would I write N= 2sp 2 ? Yes, to find the hybridization just c...
by serenabirkhoff_1K
Fri Dec 06, 2019 3:27 pm
Forum: Dipole Moments
Topic: Melting and Boiling Points
Replies: 9
Views: 176

Re: Melting and Boiling Points

Camille 4I wrote:What makes for a higher boiling point, ion-dipole interactions or hydrogen bonding?


Ion-dipole interactions are the strongest intermolecular force and therefore stronger than hydrogen bonding and therefore ion-dipole interactions have a higher boiling point.
by serenabirkhoff_1K
Fri Dec 06, 2019 3:23 pm
Forum: Sigma & Pi Bonds
Topic: Sigma vs. Pi
Replies: 15
Views: 320

Re: Sigma vs. Pi

Sigma bonds are stronger and this makes sense because if the molecule rotates pi bonds will be broken.
by serenabirkhoff_1K
Fri Dec 06, 2019 3:20 pm
Forum: Conjugate Acids & Bases
Topic: Oxoacids
Replies: 4
Views: 106

Re: Oxoacids

In addition to the problem above when the molecule is an oxoacid when drawing the lewis structure the hydrogen will be attached to the oxygen, even when the oxygen is not the central atom.
by serenabirkhoff_1K
Fri Dec 06, 2019 3:16 pm
Forum: Naming
Topic: H20 vs 0H-
Replies: 2
Views: 44

Re: H20 vs 0H-

AnnikaMittelhauser4E wrote:I think you might be misreading the answers. Aqua always refers to water, which can be written as either H2O or OH2 (which I think you're mistaking for OH-). The textbook writes water as OH2 to emphasize the oxygen is doing the bonding I believe.

Thank you this makes a lot more sense now!!
by serenabirkhoff_1K
Fri Dec 06, 2019 3:15 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4802

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

For number 4 how does the hybridization become sp2 if there are 4 p electrons and 2 s electrons? If you draw the lewis structures you will see there are 3 regions of electron density around S, one lone pair and 2 bonds with 0. (remember a double bond still counts as one region of electron density)....
by serenabirkhoff_1K
Sun Dec 01, 2019 8:03 pm
Forum: Naming
Topic: H20 vs 0H-
Replies: 2
Views: 44

H20 vs 0H-

When given the name and expected to write the formula for coordination compounds how do you know when given aqua to use H2O or OH-
For Example in 9c.3 part 3 has aqua and in the answer it says to use H2O but in part d aqua is in the name but they use OH- when writing the formula.
by serenabirkhoff_1K
Sun Dec 01, 2019 3:00 pm
Forum: Naming
Topic: Ligands
Replies: 6
Views: 72

Re: Ligands

You would do well to memorize the table. If you forget you can try drawing the Lewis structure to figure it out, but this is difficult for more complicated ligands https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/NamingCoordinationCompounds.pdf is this the table you are referring t...
by serenabirkhoff_1K
Sun Dec 01, 2019 2:57 pm
Forum: Naming
Topic: Final Exam?
Replies: 20
Views: 197

Re: Final Exam?

It is cumulative and I would make sure to know everything on each of the outlines as well as be able to do the problems on them. All the outline and the problems are on his website.
by serenabirkhoff_1K
Sun Dec 01, 2019 2:55 pm
Forum: Naming
Topic: Roman Numeral
Replies: 13
Views: 96

Re: Roman Numeral

If we use the roman numeral for positive cations what do we use if the transition metal has a negative anion charge? will this happen?
by serenabirkhoff_1K
Sat Nov 30, 2019 6:33 pm
Forum: Hybridization
Topic: Hybridization and the Octet Rule
Replies: 3
Views: 54

Re: Hybridization and the Octet Rule

For part b i meant to put that it is BH3 so that would change the reasoning would it still be the case with this?
by serenabirkhoff_1K
Sat Nov 30, 2019 6:21 pm
Forum: Hybridization
Topic: Hybridization and the Octet Rule
Replies: 3
Views: 54

Hybridization and the Octet Rule

When doing a hybridization problem like 2F5 part b (it says to identify the hybrid orbital for BrF3) is it possible for the lewis structure to not satisfy the octet rule? and to solve this problem do you just count the numbers of electron density?
by serenabirkhoff_1K
Fri Nov 29, 2019 8:45 pm
Forum: Lewis Acids & Bases
Topic: Bronsted and Lewis Acids
Replies: 4
Views: 52

Re: Bronsted and Lewis Acids

Thank you so much. I was a bit confused on the difference, but this helped a lot.
by serenabirkhoff_1K
Fri Nov 29, 2019 8:41 pm
Forum: Naming
Topic: Any Givens During the Final?
Replies: 4
Views: 143

Re: Any Givens During the Final?

I think that we will be given the same information on the final as the tests and midterms. For learning how to name the coordination compounds, Dr. Lavelle posted a sheet for this on his page, which I think we must memorize/learn for the final. Here is the sheet. https://lavelle.chem.ucla.edu/wp-con...
by serenabirkhoff_1K
Fri Nov 22, 2019 3:44 pm
Forum: Naming
Topic: Naming
Replies: 6
Views: 86

Re: Naming

In addition to the link given above with the pdf of how to name compounds and what names we should know shared by Dr. Lavelle, I would also suggest doing the practice problems on outline 5 to understand better what compounds we will be expected to name and also have practice naming them, and then ho...
by serenabirkhoff_1K
Fri Nov 22, 2019 3:39 pm
Forum: Dipole Moments
Topic: Polar or Nonpolar
Replies: 5
Views: 105

Re: Polar or Nonpolar

Additionally, there is a table on page 113 in the textbook that helped me a lot with understanding polar and nonpolar. It also helped visualize polar and nonpolar with the shape of the molecule and VSEPR formula, withe examples. The figure is 2E.7 on page 113.
by serenabirkhoff_1K
Fri Nov 22, 2019 3:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bent v. angular
Replies: 20
Views: 337

Re: bent v. angular

Bent and angular are interchangeable terms for the same type of shape. Both work when naming AX2E and AX2E2 molecules. Additionally, AX2E and AX2E2 are both bent/angular shape but have different angles depending on how many electron pairs they have. AX2E has one electron pair and the bond angles are...
by serenabirkhoff_1K
Fri Nov 22, 2019 2:33 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 9 Homework
Replies: 2
Views: 39

Week 9 Homework

For week 9 I am assuming we still have to do 5 problems. When do we turn in our homework if we do not have section? Do we just turn it in to our TA during lecture or the following week do we turn in week 9 and 10.
by serenabirkhoff_1K
Fri Nov 22, 2019 2:29 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Homework
Replies: 1
Views: 22

Re: Homework

For next week (week 9) I think we can do outline 5 and the start of outline 6.
by serenabirkhoff_1K
Tue Nov 19, 2019 10:40 pm
Forum: General Science Questions
Topic: Test 2
Replies: 7
Views: 126

Re: Test 2

We are definitely supposed to memorize all the shapes we learned in class. As well as what we learned after like bond angles and how they can change based on lone pairs.
by serenabirkhoff_1K
Thu Nov 14, 2019 11:27 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Will we need to know these VSEPR shapes as well?
Replies: 10
Views: 115

Re: Will we need to know these VSEPR shapes as well?

I would just worry about what we learned for right now, but he said he will be going over more in Fridays lecture so he might go over those then, and then they will probably be on the test.
by serenabirkhoff_1K
Thu Nov 14, 2019 11:25 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Arrangement vs Shape
Replies: 3
Views: 25

Re: Arrangement vs Shape

I am not sure exactly what you mean, but when drawing the lewis structure you have to arrange the atoms equally distant from the central atom and then once you do this you can determine the name of the shape based on the arrangement of the atoms. For example, the a linear or trigonal planar shape ba...
by serenabirkhoff_1K
Thu Nov 14, 2019 11:20 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Memorization
Replies: 15
Views: 175

Re: Memorization

Yes definitely memorize the names he said when asked questions on this topic we will have to name the shape.
by serenabirkhoff_1K
Thu Nov 14, 2019 11:19 am
Forum: Administrative Questions and Class Announcements
Topic: Test 2
Replies: 7
Views: 74

Re: Test 2

Thank you! So glad it is only on the topics covered after the midterm.
by serenabirkhoff_1K
Thu Nov 14, 2019 11:17 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: dipole moment clarification
Replies: 6
Views: 43

Re: dipole moment clarification

I found this definition for a dipole moment and it helped me a lot hope it helps. When atoms in a molecule share electrons unequally, they create what is called a dipole moment. This occurs when one atom is more electronegative than another, resulting in that atom pulling more tightly on the shared ...
by serenabirkhoff_1K
Thu Nov 14, 2019 11:11 am
Forum: Administrative Questions and Class Announcements
Topic: Test #2
Replies: 22
Views: 2124

Re: Test #2

Julieta Serobyan4D wrote:My TA told me it's going to include VSEPR, IMF, polarity and bonding.


Have we covered IMF in class yet? what section in textbook is it?
by serenabirkhoff_1K
Thu Nov 14, 2019 11:06 am
Forum: Administrative Questions and Class Announcements
Topic: TEST 2
Replies: 8
Views: 85

Re: TEST 2

What section is intermolecular forces?
by serenabirkhoff_1K
Mon Nov 04, 2019 5:36 pm
Forum: Ionic & Covalent Bonds
Topic: Names and chemical formulas
Replies: 5
Views: 50

Names and chemical formulas

Do we need to know formulas for certain chemical compounds like Ammonium? One of the homework problems asked to draw a lewis structure with ammonium and another element but did not give you (NH4+). Will we need to know this for the midterm and if so which others should I memorize? I know he said to ...
by serenabirkhoff_1K
Mon Nov 04, 2019 5:31 pm
Forum: Lewis Structures
Topic: How do I know when to use a double bond?
Replies: 7
Views: 95

Re: How do I know when to use a double bond?

If you have an odd number of electrons like when oxygen makes one bond and then has 5 extra electrons there is one extra electron to create 3 lone pairs of electron so you can create a double bond to have 4 electrons which is an even number for the lone pairs
by serenabirkhoff_1K
Mon Nov 04, 2019 5:10 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Easier way to calculate/remember?
Replies: 7
Views: 185

Re: Easier way to calculate/remember?

for me the easiest way to remember how to calculate formal charge is the formula. At first I was having trouble remembering but once you do enough practice problems with the formula you should remember it.
by serenabirkhoff_1K
Mon Nov 04, 2019 5:09 pm
Forum: Bond Lengths & Energies
Topic: 2D.19
Replies: 2
Views: 41

Re: 2D.19

For D.19 use the table 2d11 with the given the radii for each element and add the two radii together to get your answer. For example for part A you get from the graph 77pm for C and 58pm for F and then just add them together to get the answer 135pm
by serenabirkhoff_1K
Mon Nov 04, 2019 3:33 pm
Forum: Lewis Structures
Topic: formal charge
Replies: 4
Views: 67

Re: formal charge

FC = [# of valence electrons on atom] – [(# of lone pair electrons) + (# of shared electrons)/2] Formal charge helps you predict which structure is the lowest energy structure. The closer the formal charges are to 0 on the atoms the lower the energy of the structure. It is important to calculate for...
by serenabirkhoff_1K
Thu Oct 31, 2019 12:31 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 2
Views: 45

Re: Midterm

Yes the midterm covers all material up to the end of Focus 2D in Outline 3: Chemical Bonds.
by serenabirkhoff_1K
Thu Oct 31, 2019 12:30 pm
Forum: Lewis Structures
Topic: Creating Lewis Structures
Replies: 7
Views: 89

Re: Creating Lewis Structures

The atom with the lowest ionization energy goes in the middle. Remember that ionization energy increases as you move up and right on the periodic table. Ionization energy is the minimum amount of energy required to remove the most loosely bound electron.
by serenabirkhoff_1K
Thu Oct 31, 2019 12:28 pm
Forum: Lewis Structures
Topic: Drawing lewis structures
Replies: 8
Views: 74

Re: Drawing lewis structures

He said in lecture that we have not learned angles yet and we will learn it later so right now drawing angles is not needed.
by serenabirkhoff_1K
Thu Oct 31, 2019 12:26 pm
Forum: Ionic & Covalent Bonds
Topic: Homework for Week 5
Replies: 8
Views: 79

Re: Homework for Week 5

i think you are supposed to do it on the most recent topic but I am sure if you do a few quantum and a few chemical bonding that is okay too.
by serenabirkhoff_1K
Thu Oct 31, 2019 12:24 pm
Forum: Electronegativity
Topic: Electronegativity vs. Electron Affinity
Replies: 7
Views: 80

Re: Electronegativity vs. Electron Affinity

To add to this: Electronegativity is how well an atom can attract an electron to itself. This increases as you move right on the periodic table. Electron affinity of an atom or molecule is defined as the amount of energy released or spent when an electron is added to a neutral atom. Electron affinit...
by serenabirkhoff_1K
Tue Oct 22, 2019 11:00 pm
Forum: Administrative Questions and Class Announcements
Topic: Online Modules
Replies: 7
Views: 92

Re: Online Modules

I don't think there will be any more. I think based on the survey's and how much people liked them he may work on adding more in the future.
by serenabirkhoff_1K
Tue Oct 22, 2019 10:59 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Atomic radius vs. Ionic radius
Replies: 5
Views: 51

Re: Atomic radius vs. Ionic radius

The atomic radius refers to the radius of atoms in ground state (i.e. lowest energy state of an atom, which we can consider electrically neutral). The ionic radius refers to the radius of ions -- atoms with charge -- which are different in size from atoms in neutral state. The ionic radius of an io...
by serenabirkhoff_1K
Tue Oct 22, 2019 10:58 pm
Forum: Properties of Electrons
Topic: Electron Transitions
Replies: 1
Views: 79

Re: Electron Transitions

Someone on another post said this and it helped me hope it does the same! "Atomic spectra are the transitions of electrons between electronic energy levels in isolated atoms. They are affected by interactions of the transitioning electrons with the nuclei spins and with the other electrons in t...
by serenabirkhoff_1K
Tue Oct 22, 2019 10:46 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: s, p, d, f orbitals
Replies: 15
Views: 167

Re: s, p, d, f orbitals

The 4s orbitals have a lower energy than the 3d, and so the 4s orbitals are filled first. When writing electron configurations the order in the orbitals are filled in increasing order of energy levels so 4s would come before 3d.
by serenabirkhoff_1K
Tue Oct 22, 2019 10:36 pm
Forum: *Particle in a Box
Topic: cations and anions
Replies: 5
Views: 169

Re: cations and anions

An atom is considered to be a cation when it's lost an electron(s) from its neutral state and is thus positive (a common method used to remember this is that "cats" are paws-itive). On the other hand, if an atom gains an electron(s), it becomes more negative and is considered to be an ani...
by serenabirkhoff_1K
Tue Oct 22, 2019 10:30 pm
Forum: Properties of Electrons
Topic: 1A.11
Replies: 2
Views: 64

1A.11

Can someone explain the answer to question 1A.11 I am not sure on the concept here
by serenabirkhoff_1K
Sat Oct 19, 2019 12:17 pm
Forum: Balancing Chemical Reactions
Topic: HW Question L35
Replies: 2
Views: 126

Re: HW Question L35

This problem has an error in the solution manual.
Here is the link Dr. Lavelle shared
https://lavelle.chem.ucla.edu/wp-conten ... rs_7Ed.pdf
by serenabirkhoff_1K
Sat Oct 19, 2019 12:16 pm
Forum: SI Units, Unit Conversions
Topic: How to express answers
Replies: 13
Views: 265

Re: How to express answers

I don't believe that sig figs are too important in this class. My TA told us that sig figs are not too big of a deal, as long as you do not round to whole numbers or to only 1 decimal place when the answer should clearly have 2 or 3 decimal places. As for scientific notation, I believe that it is m...
by serenabirkhoff_1K
Sat Oct 19, 2019 12:10 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: HW 1D.19
Replies: 2
Views: 29

Re: HW 1D.19

a) 3 b) 5 c) 1 d) 7
by serenabirkhoff_1K
Sat Oct 19, 2019 12:05 pm
Forum: Properties of Light
Topic: Quantum equations
Replies: 5
Views: 57

Re: Quantum equations

The unit of the de Broglie wavelength is meters (m) so when using his formula I think it should be in m but after solving you can convert to nm for the answer if it asks.
by serenabirkhoff_1K
Sat Oct 19, 2019 12:00 pm
Forum: Administrative Questions and Class Announcements
Topic: chemistry community comments
Replies: 4
Views: 115

Re: chemistry community comments

Rich Zodda 4B wrote:What kind of posts count? Like do questions about grading such as this one count?


I think all comments and questions count from what I heard.
by serenabirkhoff_1K
Sat Oct 19, 2019 11:57 am
Forum: Properties of Light
Topic: Midterm Exam
Replies: 21
Views: 255

Re: Midterm Exam

Sanjana Munagala_3k wrote:From what I heard from my TA. It won't really cover fundamentals but will cover the quantum world and chemical bonding!

Hope that helps!



If it covers chemical bonding do you know when we will start learning this since the midterm is coming up?
by serenabirkhoff_1K
Sat Oct 19, 2019 11:52 am
Forum: SI Units, Unit Conversions
Topic: Unit conversion
Replies: 15
Views: 488

Re: Unit conversion

Thank you all so much this helped a lot!!
by serenabirkhoff_1K
Sun Oct 13, 2019 12:56 pm
Forum: Significant Figures
Topic: How many significant figures are in 7.00 x 10^2?
Replies: 12
Views: 315

Re: How many significant figures are in 7.00 x 10^2?

Thank you so much all these responses helped a lot to know the difference in sig figs when using scientific notation like 7.00 x 10^2 versus 7 x 10^2.
by serenabirkhoff_1K
Sun Oct 13, 2019 12:52 pm
Forum: Empirical & Molecular Formulas
Topic: Polyatomic Ions/Naming Compounds
Replies: 6
Views: 256

Re: Polyatomic Ions/Naming Compounds

Will we ever have to know the polyatomic ions or always just the simple ones like water and carbon dioxide?
by serenabirkhoff_1K
Sun Oct 13, 2019 12:50 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Reactions
Replies: 20
Views: 483

Re: Balancing Chemical Reactions

I always start with what looks most complicated and leave elements that stand alone for last because when adding a coefficient to that element it will not change the amount for others and therefore is easier to change last because then you do not have to go back and add more coefficients to other el...
by serenabirkhoff_1K
Sun Oct 13, 2019 12:44 pm
Forum: SI Units, Unit Conversions
Topic: Unit conversion
Replies: 15
Views: 488

Unit conversion

How do you convert to angstroms to other units and from other units to angstroms?
by serenabirkhoff_1K
Sat Oct 12, 2019 9:51 pm
Forum: Significant Figures
Topic: Significant Figures
Replies: 6
Views: 211

Re: Significant Figures

I agree with everything Rebekah said! To add onto it, sig figs are important when calculating your final answer. For example, if you were multiplying two numbers - 2.0 (2 sig figs) and 554.0 (4 sig figs) - your answer would have as many sig figs as the value with the lowest number of sig figs. The ...
by serenabirkhoff_1K
Sat Oct 12, 2019 9:51 pm
Forum: Significant Figures
Topic: Significant Figures
Replies: 6
Views: 211

Re: Significant Figures

I agree with everything Rebekah said! To add onto it, sig figs are important when calculating your final answer. For example, if you were multiplying two numbers - 2.0 (2 sig figs) and 554.0 (4 sig figs) - your answer would have as many sig figs as the value with the lowest number of sig figs. The ...
by serenabirkhoff_1K
Thu Oct 03, 2019 4:52 pm
Forum: Limiting Reactant Calculations
Topic: Homework Week 1
Replies: 18
Views: 293

Re: Homework Week 1

I understand it is 5 problems each week but how is it graded? Is it completely by accuracy?
by serenabirkhoff_1K
Thu Oct 03, 2019 4:50 pm
Forum: Balancing Chemical Reactions
Topic: "Combustion" Term
Replies: 8
Views: 183

Re: "Combustion" Term

Each term burning, combustion, oxidation, or metabolism from my understanding are used depending on the molecules that are in that reaction.
by serenabirkhoff_1K
Thu Oct 03, 2019 4:46 pm
Forum: Administrative Questions and Class Announcements
Topic: chemistry community comments
Replies: 4
Views: 115

chemistry community comments

We are required to post 5 comments per week in order to receive full credit correct? How do the TAs check this? Do we show them our comments for the week during discussion?
by serenabirkhoff_1K
Thu Oct 03, 2019 4:41 pm
Forum: Student Social/Study Group
Topic: Study Group Fall 2019
Replies: 32
Views: 1693

Re: Study Group Fall 2019

305319402 wrote:when would we meet for study groups? also can someone maybe make a groupme for the study group?


I think a group me would be easiest if someone can make one! and we can meet in any of the study rooms around campus I know there are ones you can reserve in the study!
by serenabirkhoff_1K
Thu Oct 03, 2019 4:40 pm
Forum: Student Social/Study Group
Topic: Study Group Fall 2019
Replies: 32
Views: 1693

Re: Study Group Fall 2019

I am interested!! Does anyone know of one already started? If so can I be added? If not we should really start one!
by serenabirkhoff_1K
Thu Oct 03, 2019 4:34 pm
Forum: Balancing Chemical Reactions
Topic: Fractions in front of compounds
Replies: 12
Views: 152

Re: Fractions in front of compounds

Just like in an math equation what you do to one side you must do to another. The easiest way for me to think about it is if you have a fraction and need to make is a whole number, multiple every coefficient by the denominator of that fraction (including that fraction), in order to get a balanced eq...

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