Search found 60 matches

by KatrinaPho_2I
Sat Mar 16, 2019 12:21 pm
Forum: Student Social/Study Group
Topic: Studying for the Final
Replies: 25
Views: 542

Re: Studying for the Final

My TA Joyce posts amazingly detailed review worksheets for each week. Bless her soul. Here's a link for Week 10: viewtopic.php?f=150&t=44734&p=154737&hilit=joyce&sid=67f6ec9f28f13271bf8509808c47037e#p154737
by KatrinaPho_2I
Sat Mar 16, 2019 12:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Phases Cell Diagram
Replies: 2
Views: 41

Re: Phases Cell Diagram

If you have multiple, solids, separate them by a line, not a comma. This is because the solids cannot mix.
by KatrinaPho_2I
Sun Mar 10, 2019 4:13 pm
Forum: General Rate Laws
Topic: Rate Determining Step
Replies: 5
Views: 53

Re: Rate Determining Step

Yup! the slowest step, or the step with the highest activation rate, is the slowest rate. The slowest rate is always the rate that determines the rate of the reaction.
by KatrinaPho_2I
Sun Mar 10, 2019 4:08 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: reaction intermediates
Replies: 2
Views: 36

Re: reaction intermediates

Reaction intermediates are the reactants and products that end up canceling out when you write out all of the steps that it takes to get to the final product.
by KatrinaPho_2I
Sun Mar 10, 2019 3:59 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 2 averages
Replies: 4
Views: 95

Re: Test 2 averages

While my discussion section's average was around 38/50, I believe the class as a total had a slightly lower average. This test was a killer one :(
by KatrinaPho_2I
Mon Mar 04, 2019 1:03 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Study Advice
Replies: 30
Views: 364

Re: Study Advice

If you look up the worksheets that the TA Joyce posts on chem community, they are really helpful. Lyndon's review sessions are also very helpful.
by KatrinaPho_2I
Mon Mar 04, 2019 12:57 am
Forum: Student Social/Study Group
Topic: Final
Replies: 24
Views: 568

Re: Final

Lyndon's review sessions are usually a few days before the final.
by KatrinaPho_2I
Mon Mar 04, 2019 12:55 am
Forum: Administrative Questions and Class Announcements
Topic: Homework
Replies: 7
Views: 119

Re: Homework

Usually it is expected to do hw from the current chapter in the textbook. I think it is okay if you include a few problems from one chapter earlier if it is being covered in a test.
by KatrinaPho_2I
Fri Feb 22, 2019 11:42 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: units
Replies: 7
Views: 177

Re: units

If you ever get pressure given int he units of "bar", you can just assume that its a 1:1 ratio with "atm". The conversion factor is very close to one, so Lavelle said we can treat bar as equal to atm.
by KatrinaPho_2I
Fri Feb 22, 2019 11:37 am
Forum: Student Social/Study Group
Topic: Midterm Results
Replies: 4
Views: 103

Re: Midterm Results

When you get your midterm back, you can review your score and your answers using this link: https://lavelle.chem.ucla.edu/wp-conten ... am_ans.pdf

IF you want to dispute your score, make sure to double check the answer key first.
by KatrinaPho_2I
Fri Feb 22, 2019 11:35 am
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Recharging Batteries [ENDORSED]
Replies: 8
Views: 179

Re: Recharging Batteries [ENDORSED]

For batteries to be recharged, the reaction has to be reversed and electrical energy has to be supplied. Because we have to supply and input energy, this is not favorable.
by KatrinaPho_2I
Wed Feb 20, 2019 4:39 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 5/2R vs 3/2R
Replies: 4
Views: 181

Re: 5/2R vs 3/2R

These values only work if you are dealing with monoatomic ideal gases.
by KatrinaPho_2I
Wed Feb 20, 2019 4:35 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: What is pKa and Ka exactly?
Replies: 11
Views: 496

Re: What is pKa and Ka exactly?

Ka is [product]/[reactant] in an acidic reaction. pKa is simply the neg log of Ka.
by KatrinaPho_2I
Wed Feb 20, 2019 4:32 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 5
Views: 70

Re: Salt Bridge

Another note is salt bridges have the same purpose as porous discs. The only difference is salt bridges connect the solutions between two different containers while porous discs connect the solutions separated in the same container.
by KatrinaPho_2I
Sun Feb 10, 2019 9:28 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Midterm
Replies: 2
Views: 62

Re: Midterm

14B-1, 11am class:
Last name A-L in DODD 147.
Last name M-Z in LAKRETZ 110.

14B-2, 1pm class:
Last name A-L in HAINES 39.
Last name M-Z in FRANZ 1178.

14B-4, 3pm class: Last name A-Z in MOORE 100.
by KatrinaPho_2I
Sun Feb 10, 2019 1:59 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: midterm
Replies: 3
Views: 93

Re: midterm

https://lavelle.chem.ucla.edu/wp-conten ... ns_14B.pdf <--- this link lists all of the available hours in these few days.
by KatrinaPho_2I
Sun Feb 10, 2019 1:50 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Converting Celsius to Kelvin
Replies: 7
Views: 100

Re: Converting Celsius to Kelvin

So far, simply adding 273 has worked well for me.
by KatrinaPho_2I
Mon Feb 04, 2019 3:19 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed and Isolated
Replies: 10
Views: 125

Re: Closed and Isolated

The plant as a whole interacts with the environment in terms of mass (O2, CO2, water) and energy (sunlight and thermal).
by KatrinaPho_2I
Mon Feb 04, 2019 3:14 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Midterm [ENDORSED]
Replies: 48
Views: 931

Re: Midterm [ENDORSED]

LYNDON BUI WILL BE YOUR BEST FRIEND. Make sure you go to all of the review sessions that you can make. They will cover the most important topics and give you example questions that will prepare you well for the major tests.
by KatrinaPho_2I
Mon Feb 04, 2019 3:10 pm
Forum: Administrative Questions and Class Announcements
Topic: Final from 14A
Replies: 2
Views: 137

Re: Final from 14A

Right when you walk into the front of Young Hall, the office people should have your test. You just have to ask for the Chem 14 A Final and they'll take your bruincard and they'll give you your final right away.
by KatrinaPho_2I
Sun Jan 27, 2019 2:25 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes
Replies: 7
Views: 96

Re: Phase Changes

To turn ice to water (melting), heat must be added to the system (endothermic). In ice, the molecules have very little movement, adding heat energy to this increases the kinetic energy of the molecules, pushing it through a phase change and melting into water. The same is true for vaporization where...
by KatrinaPho_2I
Sun Jan 27, 2019 2:23 pm
Forum: Phase Changes & Related Calculations
Topic: Phase changes
Replies: 14
Views: 134

Re: Phase changes

Yes, to turn ice to water (melting), heat must be added to the system (endothermic) and the molecules move around quicker and melt. To turn water into ice (freezing), the water loses heat energy (exothermic) and the molecules slow down in movement and freeze into a solid.
by KatrinaPho_2I
Sun Jan 27, 2019 2:20 pm
Forum: Phase Changes & Related Calculations
Topic: State Property
Replies: 3
Views: 51

Re: State Property

I understand state properties as values that are added and subtracted to find simple relationships of position. For example, the positions of two people can be compared. Person #1 is at the 5 meter mark while Person #2 is at the 8 meter mark. It doesn't matter how quickly someone traveled, what path...
by KatrinaPho_2I
Thu Jan 17, 2019 11:31 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Tables [ENDORSED]
Replies: 11
Views: 148

Re: ICE Tables [ENDORSED]

ICE tables are typically used when finding the equilibrium concentrations of weak acids and bases. This is because with weak acids and bases, they don't fully dissociate and we have to calculate the specific concentrations of each reactant and product.
by KatrinaPho_2I
Thu Jan 17, 2019 11:26 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Approximation of x
Replies: 3
Views: 117

Re: Approximation of x

Just keep in mind that only the x in the (reactant-x) is negligible. The other changes in concentration for the products still have to be considered.
by KatrinaPho_2I
Thu Jan 17, 2019 11:17 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE tables
Replies: 3
Views: 44

Re: ICE tables

The stoichiometric coefficients will be the same coefficients that you put in the "change" part of the table. If the coefficient is 1, the change will be =/- x. If the coefficient is 3, the change will be =/- 3x.
by KatrinaPho_2I
Wed Jan 09, 2019 3:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Stability
Replies: 3
Views: 36

Re: Stability

Reactions will try to reach the most stable state as it reaches equilibrium. If products are more stable, more products will be produced and its concentration will be higher than the reactant concentration. This leads to a Higher K value. If reactants are more stable, the reactants will not react as...
by KatrinaPho_2I
Wed Jan 09, 2019 3:24 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: example in class
Replies: 3
Views: 56

Re: example in class

He simply set up an ICE table with the provided information and the assumption that the initial concentrations of AD and Pi were 0 initially. With the initial and equilibrium concentrations of ADP provided in the problem, he calculated the change in concentration for ADP. Because the molar ratios of...
by KatrinaPho_2I
Wed Jan 09, 2019 3:17 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE Tables
Replies: 3
Views: 78

Re: ICE Tables

This video should help you understand the basics of the ICE Tables by giving you a few examples: https://www.youtube.com/watch?v=aJ0KNQ5-KaI

The ICE tables help you calculate concentrations when dealing with reactions in equilibrium.
by KatrinaPho_2I
Fri Dec 07, 2018 12:02 pm
Forum: Conjugate Acids & Bases
Topic: Inductive Effect
Replies: 5
Views: 115

Re: Inductive Effect

I consider the inductive effect as a fancy name for the same concept we already know about electronegativity and it’s effect on electron distribution. The more electronegative the atom, the more even the electron distribution is, and the more stable the molecule is. The more stable the molecule, the...
by KatrinaPho_2I
Fri Dec 07, 2018 12:00 pm
Forum: Air Pollution & Acid Rain
Topic: acid rain
Replies: 4
Views: 135

Re: acid rain

The importance of this is recognizing that nonmetal oxides react with water and produce acidic products.
by KatrinaPho_2I
Fri Dec 07, 2018 11:58 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate
Replies: 3
Views: 39

Re: Polydentate

Polydentates should have more than one element with lone pairs.
by KatrinaPho_2I
Sun Dec 02, 2018 10:33 pm
Forum: Hybridization
Topic: Sigma bonds
Replies: 9
Views: 126

Re: Sigma bonds

All first bonds are sigma bonds. Any of the bonds on top of the first are considered pi bonds.
by KatrinaPho_2I
Sun Dec 02, 2018 10:30 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: LDF
Replies: 7
Views: 145

Re: LDF

While LDF is found between all molecules, it would only be important to point this out when dealing with two non-polar molecules.
by KatrinaPho_2I
Sun Dec 02, 2018 10:29 pm
Forum: Hybridization
Topic: Double and Triple Bonds
Replies: 17
Views: 203

Re: Double and Triple Bonds

Ignore the bonds and simply pay attention to ares of electron density to determine hybridization.
by KatrinaPho_2I
Sun Dec 02, 2018 10:23 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: How to draw dipoles
Replies: 3
Views: 81

Re: How to draw dipoles

I believe that within a molecule, you draw dipoles for each bond. When looking at the bond, you compare the two elements' electronegativity. Parallel to the bond, draw an arrow that points towards the element that is more electronegative. .
by KatrinaPho_2I
Sun Dec 02, 2018 10:17 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Sigma and Pi Bonds
Replies: 6
Views: 203

Re: Sigma and Pi Bonds

Yep! Every first bond is a sigma bond. Any other bond added on top of the first ones are considered pi bonds.
by KatrinaPho_2I
Sun Dec 02, 2018 10:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Square Planar
Replies: 12
Views: 193

Re: Square Planar

All the angles in a square planar molecule are 90 degrees. You can easily remember this by recalling that a 2-d square is made up of 90 degree angles.
by KatrinaPho_2I
Sun Nov 18, 2018 9:54 pm
Forum: Properties of Light
Topic: Test 3
Replies: 24
Views: 494

Re: Test 3

My TA Anton listed these topics for Test 3: Bonding (trends), Shape (lewis structure), Molecular Shape, Polarity, and Hybridization.
by KatrinaPho_2I
Sun Nov 18, 2018 9:40 pm
Forum: Sigma & Pi Bonds
Topic: Visualizing sigma and pi bonds
Replies: 7
Views: 129

Re: Visualizing sigma and pi bonds

https://www.youtube.com/watch?v=D0-oOwzc8P0

This video should help you visualize the difference between sigma and pi bonding in organic molecules.
by KatrinaPho_2I
Sun Nov 18, 2018 9:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar molecules
Replies: 5
Views: 72

Re: Polar molecules

Yes, your explanation is perfect for why this molecule is polar :)
by KatrinaPho_2I
Sun Nov 11, 2018 9:39 pm
Forum: Trends in The Periodic Table
Topic: Atomic vs ionic radius
Replies: 4
Views: 158

Re: Atomic vs ionic radius

When the atom is neutral, the atomic and ionic radius are the same. This isn't true for anions and cations, though. If the atom loses an electron and becomes a cation,the atom becomes positively charged and the ionic radius is smaller than the atomic radius because the atom loses an electron energy ...
by KatrinaPho_2I
Sun Nov 11, 2018 9:26 pm
Forum: Student Social/Study Group
Topic: Study Group Chat?
Replies: 4
Views: 99

Re: Study Group Chat?

Here's a link to a messenger group chat for Chem 14A with Lavelle --> https://m.me/join/AbZf3pS8xum6RSWb
by KatrinaPho_2I
Sun Nov 11, 2018 9:22 pm
Forum: Bond Lengths & Energies
Topic: bond energy
Replies: 4
Views: 79

Re: bond energy

We will never be required to calculate bond energy on our own and it will usually be provided to us in the question. It is just good to understand that bond energy is higher for triple and double bonds compared to single bonds. This is because in triple and double bonds, there are more electrons bei...
by KatrinaPho_2I
Sun Nov 04, 2018 9:41 pm
Forum: Octet Exceptions
Topic: Radicals
Replies: 16
Views: 396

Re: Radicals

A radical is an atom, molecule, or ion that has an unpaired valence electron. These unpaired electrons make radicals highly chemically reactive. Most organic radicals have short lifetimes because of this.
by KatrinaPho_2I
Sun Nov 04, 2018 9:30 pm
Forum: Resonance Structures
Topic: Resonance with formal charge
Replies: 6
Views: 195

Re: Resonance with formal charge

Molecules may still have resonance even when the specific molecule is not in its most stable form. Resonance has nothing to do with the stability of the molecule.
by KatrinaPho_2I
Sun Nov 04, 2018 9:27 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenburg equation units
Replies: 2
Views: 124

Re: Heisenburg equation units

Uncertainty of momentum is is kg*m/s, and uncertainty of position is m. Uncertainty of velocity is m/s.
by KatrinaPho_2I
Sun Oct 28, 2018 3:07 pm
Forum: Lewis Structures
Topic: Lewis Structure Drawing
Replies: 6
Views: 78

Re: Lewis Structure Drawing

In my high school chem courses, lone pair electrons were always drawn as two separate dots while shared electrons were drawn as a line. While it may take a bit longer to draw, making this distinction helps you visualize and differentiate the electrons.
by KatrinaPho_2I
Sun Oct 28, 2018 3:04 pm
Forum: Properties of Electrons
Topic: Effective Nuclear Charge
Replies: 2
Views: 124

Re: Effective Nuclear Charge

Effective nuclear charge, as stated before, is the net positive attraction between protons in the nucleus and the valence electrons. Many different factors affect the effective nuclear charge. For example, shielding leads to decreased effective nuclear charge, increasing atom size leads to decreased...
by KatrinaPho_2I
Sun Oct 28, 2018 2:56 pm
Forum: Trends in The Periodic Table
Topic: Removing 2nd e- [ENDORSED]
Replies: 4
Views: 73

Re: Removing 2nd e- [ENDORSED]

By removing an electron, there is now a larger ratio of protons to electrons meaning that the electrons that are left are more attracted to the positive nucleus. This attraction is harder to overcome, therefore it takes more energy to remove the next electrons.
by KatrinaPho_2I
Sun Oct 21, 2018 5:29 pm
Forum: Trends in The Periodic Table
Topic: Periodic Table
Replies: 2
Views: 47

Re: Periodic Table

S-block elements are more reactive because they want to lose their extra outer valence electrons and reactions between elements typically occur to fill a shell. The valence electrons from S-block elements are easily removed and added to an element that needs electrons to be stable.
by KatrinaPho_2I
Sun Oct 21, 2018 4:41 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: What is the equation used for?
Replies: 9
Views: 173

Re: What is the equation used for?

I believe that my TA told us that for this equation, we mostly just need to understand the concept behind it and understand that the uncertainty exists because of the limits of our technology today. I would worry less about using the equation to actually solve any mathematical problems.
by KatrinaPho_2I
Sun Oct 21, 2018 4:37 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Shielding
Replies: 5
Views: 70

Re: Shielding

An analogy that helps you better understand shielding was given by Dr. Lavelle during Friday's lecture. Imagine you're camping and standing next to the campfire. The heat that you feel from the fire can be compared to the force of attraction between an electron and the nucleus. If someone stands bet...
by KatrinaPho_2I
Sat Oct 13, 2018 2:53 pm
Forum: Properties of Electrons
Topic: energy transitions
Replies: 6
Views: 94

Re: energy transitions

When electrons transition from one energy level to another, energy is released as photons of light. But the type of light is dependent on which energy level the electrons drops to. For example, when electrons drop to the first energy level, it releases UV light.
by KatrinaPho_2I
Sat Oct 13, 2018 2:40 pm
Forum: Photoelectric Effect
Topic: Work function
Replies: 3
Views: 60

Re: Work function

I looked through the index of the Chemical Principles 6th Edition textbook and the term workforce is never mentioned so I highly doubt it is a term we have to know or use. :)
by KatrinaPho_2I
Sat Oct 13, 2018 2:28 pm
Forum: Limiting Reactant Calculations
Topic: Test 1
Replies: 5
Views: 295

Re: Test 1

Both homework and tests should be returned the week after in your discussions :)
by KatrinaPho_2I
Wed Oct 03, 2018 10:07 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Calculating the number of atoms
Replies: 5
Views: 79

Re: Calculating the number of atoms

To go from grams to atoms, you have to do grams -> moles -> atoms. For grams -> moles, simply divide the mass (g) of the sample by its molar mass (g/mol). For moles -> atoms, multiply the # of moles * 6.022x10^23 (Avogadro's number). The final answer will be the # of atoms in the given sample.
by KatrinaPho_2I
Wed Oct 03, 2018 9:55 am
Forum: Balancing Chemical Reactions
Topic: Mole Ratios & Stoichiometric Relations
Replies: 2
Views: 97

Re: Mole Ratios & Stoichiometric Relations

Stoichiometric coefficients are the numbers written before each compound in a balanced chemical equation that represent the moles of each reactant and product. For example, 2 Na(s) + 2 H20(l) -> 2 NaOH(aq) + [1] H2(g) is the same thing as saying 2 moles Na(s) + 2 moles H20(l) -> 2 moles NaOH(aq) + 1...
by KatrinaPho_2I
Wed Oct 03, 2018 9:28 am
Forum: Photoelectric Effect
Topic: equation generated through the photoelectric experiment
Replies: 1
Views: 65

Re: equation generated through the photoelectric experiment

I believe that "C", the option you have already highlighted, is the correct answer. This is Einstein's photoelectric equation. Einstein assumed that light is made of photons and photons collide with electrons in an atom, giving all of its energy to the electron. However, some of the energy...

Go to advanced search