Search found 76 matches

by Ariel Guan 1H
Tue Jan 26, 2021 2:35 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Increase in Pressure
Replies: 31
Views: 78

Re: Increase in Pressure

you should only consider gases for pressure changes.
by Ariel Guan 1H
Tue Jan 26, 2021 2:31 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Memorize bond enthalpies / standard enthalpies of formation?
Replies: 12
Views: 31

Re: Memorize bond enthalpies / standard enthalpies of formation?

TBH I don't think he would make us memorize these; they probably will be given to us on the exam.
by Ariel Guan 1H
Tue Jan 26, 2021 2:28 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes
Replies: 12
Views: 35

Re: Phase Changes

when you go from liquid to gas, the system is heated, because in order for this to occur, bonds need to be broken.
by Ariel Guan 1H
Tue Jan 26, 2021 2:25 pm
Forum: Phase Changes & Related Calculations
Topic: Sublimation
Replies: 13
Views: 23

Re: Sublimation

For sublimation to occur, bonds would have to be broken, as a solid is changing to a gas. Since bonds are broken, this requires energy, so it's endothermic.
by Ariel Guan 1H
Tue Jan 26, 2021 2:18 pm
Forum: Phase Changes & Related Calculations
Topic: Condensation
Replies: 11
Views: 21

Re: Condensation

Condensation is when you turn water vapor into liquid, which is a reaction that loses heat, as condensation is a cooling process. so it's exothermic.
by Ariel Guan 1H
Sat Jan 23, 2021 12:35 am
Forum: Phase Changes & Related Calculations
Topic: Exothermic example
Replies: 9
Views: 28

Re: Exothermic example

when a car uses gasoline, a combustion rxn occurs, so heat is given off, and it is exothermic.
by Ariel Guan 1H
Sat Jan 23, 2021 12:27 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy units
Replies: 7
Views: 24

Re: Enthalpy units

ΔH⊖f is in kJ/mol
ΔHrxn is kJ
by Ariel Guan 1H
Thu Jan 21, 2021 12:12 am
Forum: Phase Changes & Related Calculations
Topic: Endothermic v. Exothermic
Replies: 61
Views: 163

Re: Endothermic v. Exothermic

yea, endothermic rxns will always have a positive delta H, and exothermic rxns will always have a negative delta H
by Ariel Guan 1H
Thu Jan 21, 2021 12:10 am
Forum: Phase Changes & Related Calculations
Topic: Vapor vs gas
Replies: 31
Views: 75

Re: Vapor vs gas

i think they are the same thing
by Ariel Guan 1H
Mon Jan 11, 2021 6:42 pm
Forum: Ideal Gases
Topic: PV=nRT
Replies: 74
Views: 451

Re: PV=nRT

P = pressure (atm)
V= Volume (L)
n = number of mols
R = gas constant (which is given)
T = temp (Kelvin)
by Ariel Guan 1H
Mon Jan 11, 2021 6:40 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: H2O
Replies: 44
Views: 289

Re: H2O

If H2O is a liquid or solid, you wouldn't include it. Only include H2O if it is in its gaseous form
by Ariel Guan 1H
Mon Jan 11, 2021 6:37 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Kelvin or Celsius?
Replies: 70
Views: 1378

Re: Kelvin or Celsius?

Kelvin because SI units
by Ariel Guan 1H
Mon Jan 11, 2021 6:35 pm
Forum: Ideal Gases
Topic: Units for Pressure
Replies: 41
Views: 825

Re: Units for Pressure

i think pressure should be in atm
by Ariel Guan 1H
Mon Jan 11, 2021 6:34 pm
Forum: Ideal Gases
Topic: Temperature in Ideal Gas Law
Replies: 14
Views: 62

Re: Temperature in Ideal Gas Law

Nope, you use Kelvin :))
by Ariel Guan 1H
Sat Jan 09, 2021 12:16 am
Forum: Ideal Gases
Topic: Gas constant R
Replies: 26
Views: 105

Re: Gas constant R

The gas constant R is given on equation sheets!
by Ariel Guan 1H
Wed Jan 06, 2021 11:21 am
Forum: Ideal Gases
Topic: Units of Temperature
Replies: 82
Views: 288

Re: Units of Temperature

use Kelvin because it's the SI unit.
by Ariel Guan 1H
Mon Jan 04, 2021 12:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K vs. Kc/Kp
Replies: 15
Views: 80

Re: K vs. Kc/Kp

Kc and Kp are just specifying whether we are focusing on concentration or partial pressure, but K, Kc, and Kp are all still equilibrium constants
by Ariel Guan 1H
Mon Jan 04, 2021 12:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constants
Replies: 15
Views: 163

Re: Equilibrium Constants

yea, make sure it's balanced first
by Ariel Guan 1H
Mon Jan 04, 2021 12:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reaction Direction
Replies: 19
Views: 319

Re: Reaction Direction

If Q > K then it favors left and if Q < K then it favors right
by Ariel Guan 1H
Thu Dec 10, 2020 7:57 pm
Forum: Calculating the pH of Salt Solutions
Topic: pH formula?
Replies: 46
Views: 934

Re: pH formula?

pH = -log[H+]
[H+] = 10^(-pH)
pOH = -log[OH-]
[OH-] = 10^(-pOH)
14 = pH + pOH
by Ariel Guan 1H
Thu Dec 10, 2020 7:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: wedge and dash
Replies: 14
Views: 97

Re: wedge and dash

wedge is towards you and dash is away from you; it's used to represent a structure in 3D space
by Ariel Guan 1H
Thu Dec 10, 2020 7:46 pm
Forum: Naming
Topic: Naming quizlet
Replies: 41
Views: 269

Re: Naming quizlet

yay thanks !!
by Ariel Guan 1H
Thu Dec 10, 2020 7:42 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH to pOH
Replies: 8
Views: 60

Re: pH to pOH

yea, just know that 14 = pH + pOH. Also, to find [H+] from pH, the equation is [H+] = 10^-pH, and for [OH-], [OH-] = 10^-pOH
by Ariel Guan 1H
Thu Dec 10, 2020 7:37 pm
Forum: Bronsted Acids & Bases
Topic: Identifying Strong Acids and Bases
Replies: 7
Views: 61

Re: Identifying Strong Acids and Bases

Personally this method is pretty helpful, and memorizing them is probably the easiest way.
by Ariel Guan 1H
Fri Dec 04, 2020 10:14 pm
Forum: Naming
Topic: Chelating Ligands
Replies: 3
Views: 33

Re: Chelating Ligands

yes, you are correct
by Ariel Guan 1H
Fri Dec 04, 2020 10:11 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: ligands
Replies: 11
Views: 85

Re: ligands

it's because NH3 is a neutral molecule.
by Ariel Guan 1H
Fri Dec 04, 2020 10:01 pm
Forum: Biological Examples
Topic: Enzyme Function
Replies: 8
Views: 83

Re: Enzyme Function

transition metals are located in the active sites of enzymes, and they help substrates/molecules bind to the enzyme.
by Ariel Guan 1H
Fri Dec 04, 2020 9:52 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Vinegar on a cut
Replies: 4
Views: 52

Re: Vinegar on a cut

I don't think vinegar from the chips would do a lot of damage, but if you do feel some stinging, you should probably wash your hands anyway
by Ariel Guan 1H
Thu Nov 26, 2020 3:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape Names
Replies: 50
Views: 299

Re: Shape Names

yes, it is called bent or angular.
by Ariel Guan 1H
Thu Nov 26, 2020 3:25 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: H2O VSEPR
Replies: 27
Views: 147

Re: H2O VSEPR

none of the above. it would be bent because there are 2 lone pairs
by Ariel Guan 1H
Thu Nov 26, 2020 3:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR T-Shaped Molecular Geometry
Replies: 7
Views: 69

Re: VSEPR T-Shaped Molecular Geometry

I think it's just better to know it just in case. Even if there are no q's about it, it's probably good info to know anyway.
by Ariel Guan 1H
Thu Nov 26, 2020 3:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: What does delocalized π bond mean?
Replies: 18
Views: 147

Re: What does delocalized π bond mean?

delocalized pi bonds come from molecules that have resonance structures
by Ariel Guan 1H
Thu Nov 26, 2020 3:20 pm
Forum: Electronegativity
Topic: Periodic Table Trend
Replies: 37
Views: 387

Re: Periodic Table Trend

Both follow the same trend of increasing across a period and decreasing down a group
by Ariel Guan 1H
Thu Nov 19, 2020 5:15 pm
Forum: Bond Lengths & Energies
Topic: Higher Melting Point
Replies: 27
Views: 220

Re: Higher Melting Point

CHI3 is larger than CHF3 (I is bigger than F), so the forces in CHI3 are stronger, which means that you need more energy for it to melt.
by Ariel Guan 1H
Thu Nov 19, 2020 5:04 pm
Forum: Bond Lengths & Energies
Topic: Boiling/Melting Point
Replies: 20
Views: 149

Re: Boiling/Melting Point

You look at intermolecular forces
by Ariel Guan 1H
Thu Nov 19, 2020 5:02 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: Solubility
Replies: 4
Views: 76

Re: Solubility

^^ what she said. I like to think of it as more ionic character (less covalent character) = more soluble. To figure that out, you look at the electronegativity difference; if the difference is higher, then it has a higher ionic character and is therefore more soluble. I think that molecules that can...
by Ariel Guan 1H
Wed Nov 11, 2020 8:18 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Ionic Structures
Replies: 6
Views: 35

Re: Ionic Structures

when drawing lewis structures, you want to try to get formal charges with 0 because it's most stable.
by Ariel Guan 1H
Wed Nov 11, 2020 7:58 pm
Forum: Trends in The Periodic Table
Topic: Electron affinity and Ionization energy
Replies: 7
Views: 60

Re: Electron affinity and Ionization energy

Ionization energy is the energy needed to remove electrons from an atom, while electron affinity is the amount of energy released when electrons are added to an atom.
by Ariel Guan 1H
Wed Nov 11, 2020 7:55 pm
Forum: Electronegativity
Topic: periodic table
Replies: 16
Views: 128

Re: periodic table

keely_bales_2a wrote:I found this image that has a summarization of periodic table trends. I have attached the image below. Hope you find it helpful!


this actually helps a lot- tysm!
by Ariel Guan 1H
Wed Nov 11, 2020 7:45 pm
Forum: Ionic & Covalent Bonds
Topic: Ions
Replies: 6
Views: 34

Re: Ions

I don't think it's required, but since these are very commonly used, it would be helpful to have them memorized
by Ariel Guan 1H
Wed Nov 11, 2020 7:44 pm
Forum: Sigma & Pi Bonds
Topic: Sigma vs. Pi
Replies: 20
Views: 468

Re: Sigma vs. Pi

Sigma bonds are stronger because they overlap!
by Ariel Guan 1H
Thu Nov 05, 2020 12:45 pm
Forum: Resonance Structures
Topic: Resonance Lecture Question
Replies: 10
Views: 75

Re: Resonance Lecture Question

L stands for the number of lone pair electrons! So if you were to count the lone pair e- for one atom, one dot would = one lone pair e-.
by Ariel Guan 1H
Thu Nov 05, 2020 12:43 pm
Forum: Lewis Structures
Topic: Chemical Formulas
Replies: 8
Views: 55

Re: Chemical Formulas

I feel like we will be expected to memorize the common polyatomic ions, or at least those would be good to know. So nitrate, nitrite, phosphate, phosphite, hydroxide, etc. would probably be good to know.
by Ariel Guan 1H
Thu Nov 05, 2020 12:38 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge Equation
Replies: 16
Views: 72

Re: Formal Charge Equation

L refers to the lone pair electrons. To find its value, count the amount of electrons that aren't shared, or count the amount of dots around a specific atom
by Ariel Guan 1H
Thu Nov 05, 2020 12:28 pm
Forum: Lewis Structures
Topic: Valence Electrons
Replies: 10
Views: 67

Re: Valence Electrons

Count the columns on the periodic table, but remember to exclude the transition metals. So group 13 would have 3 valence e-, group 14 would have 4, etc.
by Ariel Guan 1H
Thu Nov 05, 2020 12:25 pm
Forum: Sigma & Pi Bonds
Topic: sigma and pi bonds
Replies: 27
Views: 598

Re: sigma and pi bonds

yea, and a triple bond has one sigma bond and two pi bonds
by Ariel Guan 1H
Thu Nov 05, 2020 12:23 pm
Forum: Lewis Structures
Topic: Formal Charge and Lewis Strucutre
Replies: 3
Views: 27

Re: Formal Charge and Lewis Strucutre

I'm pretty sure the way we learned in class is the only way to calculate formal charge! but as people said earlier, with practice you should eventually get more used to calculating formal charge, and it will be a lot quicker.
by Ariel Guan 1H
Thu Oct 29, 2020 10:20 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg's
Replies: 7
Views: 56

Re: Rydberg's

yea, it only works for hydrogen atoms
by Ariel Guan 1H
Thu Oct 29, 2020 10:18 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Wave Function Quantum Numbers
Replies: 11
Views: 113

Re: Wave Function Quantum Numbers

Malakai Espinosa 3D wrote:n is the shell
l is the angular momentum(shape) of the shell
ml is the orientation of the shell, based on the axis of the nodes
ms is the spin of the electron represented as +/- 1/2


Thanks Malakai this was very helpful!! :)
by Ariel Guan 1H
Thu Oct 29, 2020 10:15 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: position units
Replies: 19
Views: 127

Re: position units

You would convert to meters! Remember that SI Units for length is in m, so you should always use meters to stay consistent
by Ariel Guan 1H
Wed Oct 28, 2020 12:07 pm
Forum: Photoelectric Effect
Topic: Work function or incoming light
Replies: 6
Views: 51

Re: Work function or incoming light

energy required to remove an electron is the work function, and the energy that caused photoejection is the energy of the incoming light
by Ariel Guan 1H
Wed Oct 28, 2020 12:02 pm
Forum: DeBroglie Equation
Topic: p
Replies: 19
Views: 171

Re: p

p is momentum which is (mass)(velocity). Some main equations you should know are p=mv, λ=h/p, and therefore λ=h/mv.
by Ariel Guan 1H
Fri Oct 23, 2020 10:28 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Finding the wavelength between two levels
Replies: 3
Views: 46

Re: Finding the wavelength between two levels

For this question, you know that the uv spectrum will end at level n=1, so you know that nfinal = 1. The equation you will be using is v = R ((1/n2^2)-(1/n1^2)). The next variable that we need to find is v (frequency), and we can do that by converting the given wavelength into meters and plugging it...
by Ariel Guan 1H
Thu Oct 22, 2020 10:56 pm
Forum: Photoelectric Effect
Topic: Intensity vs. Frequency
Replies: 22
Views: 140

Re: Intensity vs. Frequency

Intensity corresponds with the amount of photons in a particle, meaning high intensity= more photons and lower intensity = less photons. Intensity also is the amplitude of the wave in a wave model. In terms of the photoelectric effect, intensity wouldn't change the energy of the photons, which was t...
by Ariel Guan 1H
Wed Oct 21, 2020 10:44 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Electromagnetic radiation and associated energy levels
Replies: 4
Views: 44

Re: Electromagnetic radiation and associated energy levels

n=1 - Lyman Series, UV region
n=2 - Balmer Series, visible region
n=3 - Paschen Series, infrared region

I think we only need to know lyman and balmer, though.
by Ariel Guan 1H
Mon Oct 19, 2020 1:04 pm
Forum: Photoelectric Effect
Topic: What is equation is this ?
Replies: 11
Views: 76

Re: What is equation is this ?

c is the speed of light. It is used in the c=λv equation (v is frequency), however, the equation is often rearranged in terms of frequency and substituted into E=hv. The equation would then be E= (hc)/λ .
by Ariel Guan 1H
Mon Oct 19, 2020 10:52 am
Forum: DeBroglie Equation
Topic: E=pc and E=pv
Replies: 10
Views: 81

Re: E=pc and E=pv

they are the same.
by Ariel Guan 1H
Mon Oct 19, 2020 10:31 am
Forum: DeBroglie Equation
Topic: Units [ENDORSED]
Replies: 3
Views: 48

Re: Units [ENDORSED]

kg! since 1 Joule = 1kg m^2/s^2, you need to use kg so that the kg in Planck's constant can cancel out
by Ariel Guan 1H
Sat Oct 17, 2020 10:03 pm
Forum: Einstein Equation
Topic: What are the units for E
Replies: 16
Views: 124

Re: What are the units for E

The units for everything should be in Joules, since they are all Energy. Also remember that 1 Joule = 1 kg m^2 / s^2
by Ariel Guan 1H
Wed Oct 14, 2020 10:01 pm
Forum: Photoelectric Effect
Topic: Electron not emitted even for high intensity light
Replies: 9
Views: 92

Re: Electron not emitted even for high intensity light

In the lecture, he said that light wasn't acting like a wave, which means that intensity would not increase energy. He said to instead look at light as little packets of energy, and remember that one photon must have enough energy to eject one electron. However, increasing the intensity would only i...
by Ariel Guan 1H
Tue Oct 13, 2020 8:16 pm
Forum: Empirical & Molecular Formulas
Topic: Compounds can Have the Same Molecular Formulas
Replies: 4
Views: 47

Re: Compounds can Have the Same Molecular Formulas

I'm pretty sure those are called isomers. With isomers, even though the molecular formulas are the same, the structures differ (different arrangement of atoms), which is how they are different compounds
by Ariel Guan 1H
Mon Oct 12, 2020 6:37 pm
Forum: Properties of Light
Topic: Quanta and Photons
Replies: 19
Views: 172

Re: Quanta and Photons

I think it's the smallest unit/amount of something (water) that can be transferred to another object
by Ariel Guan 1H
Mon Oct 12, 2020 2:18 pm
Forum: Properties of Light
Topic: Changing Intensity vs Changing Wavelength
Replies: 7
Views: 47

Re: Changing Intensity vs Changing Wavelength

yeah, changing intensity= changing number of photons, and changing wavelength= changing energy of each one of the photons
by Ariel Guan 1H
Mon Oct 12, 2020 2:12 pm
Forum: Properties of Light
Topic: Light Intensity and Frequency
Replies: 7
Views: 82

Re: Light Intensity and Frequency

Hi, you're correct by saying that light intensity doesn't increase the energy of light. However, an increase in frequency would increase the energy of light.
by Ariel Guan 1H
Thu Oct 08, 2020 2:20 pm
Forum: Molarity, Solutions, Dilutions
Topic: Dilution Question
Replies: 5
Views: 59

Re: Dilution Question

You would use the M1V1 = M2V2 equation for this problem. You're trying to achieve a 1/5 dilution, so that means that you would need to find 1/5 of the initial molarity (given), which is 0.20M; this gives you 0.04M, which is going to be the final molarity. When you plug the three numbers into the equ...
by Ariel Guan 1H
Mon Oct 05, 2020 1:13 pm
Forum: Empirical & Molecular Formulas
Topic: Emprical Formulas Ever Larger than Molecular? [ENDORSED]
Replies: 26
Views: 458

Re: Emprical Formulas Ever Larger than Molecular? [ENDORSED]

On my screen it only says "Post Reply" in red and I don't see "New Post." This is so weird. Okay so that is because you are under the post and not the forum. Next to Board Index, click on where it says "Review of Chemical and Physical Principles". From there, you shoul...
by Ariel Guan 1H
Mon Oct 05, 2020 12:53 pm
Forum: Empirical & Molecular Formulas
Topic: Emprical Formulas Ever Larger than Molecular? [ENDORSED]
Replies: 26
Views: 458

Re: Emprical Formulas Ever Larger than Molecular? [ENDORSED]

Thank you Ariel, and I will attend his office hours for the other questions. Where does it say "New Topic" though in the top left? I only see Quick Links, Board Index, social media links in the top left area. I'm sorry if this sounds silly I just genuinely don't understand. So if you look...
by Ariel Guan 1H
Mon Oct 05, 2020 12:35 pm
Forum: Empirical & Molecular Formulas
Topic: Emprical Formulas Ever Larger than Molecular? [ENDORSED]
Replies: 26
Views: 458

Re: HELP [ENDORSED]

Guys, I have no idea how to post on this forum or contact anyone in the class but I hope Dr. Lavelle will explain it soon. I have a few questions though that maybe someone can answer: Is the code for the $72 ebook for the class from the UCLA website going to be emailed or physically mailed to my ho...
by Ariel Guan 1H
Mon Oct 05, 2020 11:05 am
Forum: Molarity, Solutions, Dilutions
Topic: Balancing Chemical Equations
Replies: 12
Views: 151

Re: Balancing Chemical Equations

When balancing an equation, if the coefficients are divisible by a common number, then you definitely should simplify. I think a good thing to keep in mind is that if you can simplify, then simplify because it usually makes calculations easier.
by Ariel Guan 1H
Mon Oct 05, 2020 10:54 am
Forum: Molarity, Solutions, Dilutions
Topic: VInitial and VFinal
Replies: 13
Views: 146

Re: VInitial and VFinal

Yea, it's used for most dilution problems I think.
by Ariel Guan 1H
Mon Oct 05, 2020 10:40 am
Forum: Molarity, Solutions, Dilutions
Topic: Molarity Example from Lecture 10/5 [ENDORSED]
Replies: 7
Views: 115

Re: Molarity Example from Lecture 10/5 [ENDORSED]

To solve the problem, use the M1V1 = M2V2 equation; plug in the values appropriately, and you should be able to find the value of V1, which is the answer. For the second question, the moles of KMnO4 doesn't change because rather than changing the amount of solute, you are changing the volume (seeing...
by Ariel Guan 1H
Mon Oct 05, 2020 10:32 am
Forum: Molarity, Solutions, Dilutions
Topic: Dilutions
Replies: 10
Views: 111

Re: Dilutions

Usually for dilutions, the changing value is the volume of solution probably due to more water being added. However, the amount of solute aka the moles stays the same. Since the volume is increasing, molarity would decrease.

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