Search found 60 matches

by KHuang1L
Sun Mar 17, 2019 4:29 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Bimolecular
Replies: 13
Views: 110

Re: Bimolecular

Bimolecular means there are two species involved in the elementary step.
by KHuang1L
Sun Mar 17, 2019 4:29 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Activation Energy
Replies: 7
Views: 56

Re: Activation Energy

Activation energy is the amount of energy required for reactant particles to collide. It is represented as the amount of energy between the transition state point and reactant or intermediate step.
by KHuang1L
Sun Mar 17, 2019 4:27 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Rate Determining Step
Replies: 9
Views: 73

Re: Rate Determining Step

The rate law is determined by the rate determining step. If there are intermediates involved, then modify the rate law so that they are not included.
by KHuang1L
Sun Mar 10, 2019 11:50 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: how is kinetics different?
Replies: 17
Views: 123

Re: how is kinetics different?

Kinetics helps us determine the rate of the reaction, while thermodynamics is used to determine whether the reaction is favorable.
by KHuang1L
Sun Mar 10, 2019 11:47 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Log version vs ln Version
Replies: 7
Views: 63

Re: Log version vs ln Version

It does not matter. But using log is more convenient when calculating for pH.
by KHuang1L
Sat Mar 02, 2019 6:46 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 7th edition 6M.5
Replies: 1
Views: 21

Re: 7th edition 6M.5

You would have to identify the half reactions and then use the standard E value of the half reactions to calculate the standard E cell value. If the E cell value is positive, then the reaction is spontaneous. If the E cell value is negative, then the reaction is not spontaneous.
by KHuang1L
Sat Mar 02, 2019 6:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 7th edition 6M.5
Replies: 1
Views: 19

Re: 7th edition 6M.5

It could just be a typo.
by KHuang1L
Sat Mar 02, 2019 6:42 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: H+ in cell diagrams
Replies: 5
Views: 56

Re: H+ in cell diagrams

Include H+ in the cell diagram when it participates in the half reactions.
by KHuang1L
Sun Feb 24, 2019 12:32 pm
Forum: Balancing Redox Reactions
Topic: Oxidating/Reducing AGENTS
Replies: 6
Views: 49

Re: Oxidating/Reducing AGENTS

An oxidizing agent is what causes something else to be oxidized, this agent is also reduced. The reducing agent is what causes something else to be reduced, this agent is also oxidized.
by KHuang1L
Sun Feb 24, 2019 12:31 pm
Forum: Balancing Redox Reactions
Topic: Test 2 Material
Replies: 11
Views: 123

Re: Test 2 Material

Material after the midterm up to week 7 material.
by KHuang1L
Sun Feb 24, 2019 12:29 pm
Forum: Balancing Redox Reactions
Topic: difference between oxidation and reduction
Replies: 8
Views: 66

Re: difference between oxidation and reduction

Oxidation is the removing of electrons and reduction is the addition of electrons.
by KHuang1L
Sat Feb 16, 2019 12:22 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Equation based on equilibrium
Replies: 5
Views: 47

Re: Equation based on equilibrium

Delta G = Delta G under standard conditions + RTlnQ is used when the reaction is not at equilibrium. When the reaction is at equilibrium, you use the equation delta G under standard conditions = -RTlnK because delta G is equal to zero and the equilibrium constant can be used.
by KHuang1L
Sat Feb 16, 2019 12:19 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs free energy
Replies: 7
Views: 60

Re: Gibbs free energy

The reaction is spontaneous when delta G is negative and not spontaneous when delta G is positive.
by KHuang1L
Sat Feb 16, 2019 12:18 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: gibbs free energy
Replies: 10
Views: 92

Re: gibbs free energy

If the change in Gibbs free energy is positive, then the reaction is not spontaneous. If the change in Gibbs free energy is negative, then the reaction is spontaneous.
by KHuang1L
Sun Feb 10, 2019 7:57 pm
Forum: Calculating Work of Expansion
Topic: Conversions to joules?
Replies: 4
Views: 66

Re: Conversions to joules?

The formula sheet has the unit conversion equation from L.atm to J. To convert cm^3 to L in your answer, the formula sheet also has the unit conversion equation from dm^3 to L.
by KHuang1L
Sun Feb 10, 2019 7:55 pm
Forum: Calculating Work of Expansion
Topic: Units
Replies: 7
Views: 68

Re: Units

The formula sheet has unit conversion equations to get to J.
by KHuang1L
Sun Feb 10, 2019 7:54 pm
Forum: Calculating Work of Expansion
Topic: Reversible vs Irreversible
Replies: 9
Views: 93

Re: Reversible vs Irreversible

The question will tell you whether it is a reversible or irreversible reaction. The work done will be different because they use different equations to calculate work. Reversible reaction: W=-PV. Irreversible reaction: W=-nrTln(V2/V1).
by KHuang1L
Fri Feb 01, 2019 9:32 pm
Forum: Phase Changes & Related Calculations
Topic: Week 4 Homework
Replies: 12
Views: 148

Re: Week 4 Homework

Anything from what we learned in week 3 and week 4.
by KHuang1L
Fri Feb 01, 2019 9:32 pm
Forum: Phase Changes & Related Calculations
Topic: What Does U and q stand for?
Replies: 9
Views: 104

Re: What Does U and q stand for?

U is internal energy and q is heat
by KHuang1L
Fri Feb 01, 2019 9:31 pm
Forum: Phase Changes & Related Calculations
Topic: Test #1
Replies: 11
Views: 136

Re: Test #1

Yes
by KHuang1L
Sat Jan 26, 2019 5:26 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy and States
Replies: 8
Views: 78

Re: Enthalpy and States

State does affect enthalpy. That is why you need to add the enthalpy of the phase change for reactions where there is a phase change.
by KHuang1L
Sat Jan 26, 2019 5:25 pm
Forum: Phase Changes & Related Calculations
Topic: Modules
Replies: 17
Views: 162

Re: Modules

No, but they are good practice.
by KHuang1L
Sat Jan 26, 2019 5:24 pm
Forum: Phase Changes & Related Calculations
Topic: Why steam causes severe burns
Replies: 9
Views: 99

Re: Why steam causes severe burns

He said that when steam (around 100 degrees C) comes into contact with skin (around 25 degrees Celsius), it releases around 40.7kJ (vaporization energy) and an additional 5kJ (to change from 100 degrees C to 25 degrees C).
by KHuang1L
Sat Jan 19, 2019 12:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When is X negligible.
Replies: 6
Views: 63

Re: When is X negligible.

X is negligible when K is less than 10^3. Also confirm that your approximation is valid if the X value is less than 5% of your initial concentration.
by KHuang1L
Sat Jan 19, 2019 12:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Gibbs Free Energy
Replies: 1
Views: 26

Re: Gibbs Free Energy

Gibbs free energy shows whether the reaction is endothermic or exothermic. A negative Gibbs free energy means that the reaction is exothermic, while a positive value means that the reaction is endothermic. I think it may be good to know.
by KHuang1L
Sat Jan 19, 2019 12:34 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endothermic
Replies: 6
Views: 93

Re: Endothermic

Heat is required in endothermic reactions, so adding heat will further the reaction.
by KHuang1L
Fri Jan 11, 2019 4:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q and K
Replies: 13
Views: 141

Re: Q and K

You calculate K by using the concentration of the reactants and products when the reaction is in equilibrium. You calculate Q by using the concentration of the reactants and products when the reaction is or is not in equilibrium. That is why Q is sometimes greater or smaller than K.
by KHuang1L
Fri Jan 11, 2019 4:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp
Replies: 9
Views: 83

Re: Kp

The question should specify whether to solve for Kp or Kc.
by KHuang1L
Thu Jan 10, 2019 8:36 pm
Forum: Ideal Gases
Topic: Q and K [ENDORSED]
Replies: 35
Views: 930

Re: Q and K [ENDORSED]

Same formulas but they calculate for different things
by KHuang1L
Sat Dec 08, 2018 11:15 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate
Replies: 11
Views: 180

Re: Polydentate

In the ligand worksheet that is on the class website, remember that ox, en, dien, and edta are all polydentate. So you would use bis and tris instead of bi and tri.
by KHuang1L
Sat Dec 08, 2018 11:13 am
Forum: Biological Examples
Topic: Ligands
Replies: 6
Views: 109

Re: Ligands

The central atom should be the transition metal.
by KHuang1L
Sat Dec 08, 2018 11:12 am
Forum: Naming
Topic: Final Exam
Replies: 9
Views: 142

Re: Final Exam

You should remember both and that it is a polydentate so you would use bis or tris to indicate the number of en molecules.
by KHuang1L
Sat Dec 01, 2018 4:14 pm
Forum: Hybridization
Topic: Hybridization Notation
Replies: 10
Views: 133

Re: Hybridization Notation

The examples in class had sp3d.
by KHuang1L
Sat Dec 01, 2018 4:13 pm
Forum: Hybridization
Topic: Pi bonds in triple bond
Replies: 17
Views: 318

Re: Pi bonds in triple bond

There is one sigma bond in a single bond, one sigma bond and one pi bond in a double bond, and one sigma bond and two pi bonds in a triple bond.
by KHuang1L
Sat Dec 01, 2018 4:11 pm
Forum: Hybridization
Topic: CH2O hybridization
Replies: 9
Views: 659

Re: CH2O hybridization

You evaluate how many regions of electron density there are (in this case there are three). So, you want a total of three hybrid orbitals, which is possible with sp2 hybridization.
by KHuang1L
Mon Nov 19, 2018 11:01 pm
Forum: Ionic & Covalent Bonds
Topic: delta positive delta negative
Replies: 15
Views: 274

Re: delta positive delta negative

The atoms with higher electronegativity are delta negative and the atoms with lower electronegativity are delta positive. If the electronegativity does not cancel out, then the molecule will be polar.
by KHuang1L
Mon Nov 19, 2018 10:59 pm
Forum: Lewis Structures
Topic: Boron Trifluoride
Replies: 8
Views: 116

Re: Boron Trifluoride

Boron is one of the element exceptions that do not follow the octet rule. It is between the element carbon (which is the first element by increasing atomic number that requires a full octet) and beryllium (an element that does not follow the octet rule). Therefore, it also doesn't require an octet.
by KHuang1L
Mon Nov 19, 2018 10:55 pm
Forum: Lewis Structures
Topic: Polar vs Nonpolar molecules
Replies: 7
Views: 107

Re: Polar vs Nonpolar molecules

Yes, check the relative electronegativity of each atom, and if the electronegativity of the atoms do not cancel out, then the molecule is polar.
by KHuang1L
Sat Nov 17, 2018 10:32 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Single Regions?
Replies: 8
Views: 132

Re: Single Regions?

You count the number of single regions of electron density to determine what molecular shape the molecule has. That means that single, double, and triple bonds are counted as just one region of electron density and count as one additional X.
by KHuang1L
Sat Nov 17, 2018 10:30 am
Forum: Determining Molecular Shape (VSEPR)
Topic: tetrahedral vs trigonal planar
Replies: 9
Views: 93

Re: tetrahedral vs trigonal planar

Tetrahedral means that there are four atoms bound around a central atom. Trigonal planar is when there are three atoms bound around a central atom. You can memorize the A, X, and E for each structure to better identify them in the future.
by KHuang1L
Sat Nov 17, 2018 10:28 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Distance from Central Atom
Replies: 8
Views: 81

Re: Distance from Central Atom

The completely shaded wedges represent atoms that are coming out of the page, while the hatched wedges represent atoms that are going into the page.
by KHuang1L
Tue Nov 06, 2018 4:34 pm
Forum: Octet Exceptions
Topic: Octet Exceptions
Replies: 3
Views: 54

Re: Octet Exceptions

H and He are exceptions because they would rather get two valence electrons to fill the 1st shell or 1s shell. B is also an exception because it is between Br, which prefers to lose two electrons to have two valence electrons, and C, which prefers to gain electrons to have a full octet.
by KHuang1L
Tue Nov 06, 2018 4:31 pm
Forum: Resonance Structures
Topic: Bond Lengths
Replies: 7
Views: 142

Re: Bond Lengths

The bond length for each N-O bond is an average of the bond lengths for all three resonance hybrids.
by KHuang1L
Tue Nov 06, 2018 4:30 pm
Forum: Resonance Structures
Topic: Most Stable Configuration
Replies: 11
Views: 156

Re: Most Stable Configuration

The most stable configuration is one where you get as many formal charges equal to zero as you can. In the case that you cannot get all formal charges equal to zero, try to change it so that the sum of all the formal charges is zero. Also, try to put the negative formal charge on the more electroneg...
by KHuang1L
Tue Oct 30, 2018 3:31 pm
Forum: Einstein Equation
Topic: Number of photons
Replies: 7
Views: 200

Re: Number of photons

E = hv gives you the energy per photon. If the question gives you the total amount of energy, then you can divide that by E to get the number of photons.
by KHuang1L
Tue Oct 30, 2018 3:30 pm
Forum: DeBroglie Equation
Topic: De Broglie
Replies: 12
Views: 287

Re: De Broglie

Use the De Broglie equation when you are trying to find the wavelength of a particle with momentum, such as an electron. You do not use the equation for light, since photons dp not have mass.
by KHuang1L
Tue Oct 30, 2018 3:28 pm
Forum: Lewis Structures
Topic: Dots in Lewis Stucture
Replies: 14
Views: 208

Re: Dots in Lewis Stucture

Professor Lavelle said that it does not matter what order you place the dots in class. However, you should make sure that there are at least 4 electrons before pairing them together.
by KHuang1L
Sat Oct 27, 2018 10:54 am
Forum: Einstein Equation
Topic: E=hv
Replies: 14
Views: 277

Re: E=hv

E is the energy of the photon. That equation is used to find the energy of a photon of light going at a certain speed. H is Planck's constant and v is the frequency of the electron. If E is equal to or greater than the threshold energy required to release an electron from an atom, then the electron ...
by KHuang1L
Sat Oct 27, 2018 10:50 am
Forum: Photoelectric Effect
Topic: Conditions that allow electron to be ejected from metal surface
Replies: 12
Views: 256

Re: Conditions that allow electron to be ejected from metal surface

Correct. If the energy of the photon is equal to the threshold energy (minimum energy required to release an electron) of the electron, then the electron is released with zero kinetic energy. If the energy of the photon is greater than the threshold energy, then the electron is released with positiv...
by KHuang1L
Sat Oct 27, 2018 10:47 am
Forum: Properties of Light
Topic: Is light in waves or photons?
Replies: 10
Views: 224

Re: Is light in waves or photons?

Light has both particle and wave-like properties. Light has particle-like properties in the photoelectric effect and wave-like properties like diffraction through the double slit experiment.
by KHuang1L
Fri Oct 19, 2018 5:01 pm
Forum: Photoelectric Effect
Topic: Threshold energy [ENDORSED]
Replies: 17
Views: 331

Re: Threshold energy [ENDORSED]

Threshold energy is basically the minimum energy required to remove an electron from an atom. The equation is energy from a photon = threshold energy + kinetic energy of the freed electron.
by KHuang1L
Fri Oct 19, 2018 4:54 pm
Forum: Properties of Light
Topic: Do I have to memorize the spectrum?
Replies: 20
Views: 268

Re: Do I have to memorize the spectrum?

He said just the wavelengths that he discussed during lecture, such as the wavelength range of visible light and UV light.
by KHuang1L
Fri Oct 19, 2018 4:53 pm
Forum: Properties of Light
Topic: Test 2 [ENDORSED]
Replies: 15
Views: 236

Re: Test 2 [ENDORSED]

Everything we learned last week up to today's lecture.
by KHuang1L
Sat Oct 13, 2018 9:28 pm
Forum: Administrative Questions and Class Announcements
Topic: Number of questions on test one [ENDORSED]
Replies: 39
Views: 17233

Re: Number of questions on test one [ENDORSED]

Around 8 questions but with multiple parts. For this test there is not much emphasis on sig figs and units.
by KHuang1L
Sat Oct 13, 2018 9:23 pm
Forum: Empirical & Molecular Formulas
Topic: Going from empirical to Molecular formula
Replies: 14
Views: 380

Re: Going from empirical to Molecular formula

It should be a whole number. First check to make sure that your work leading up to the empirical formula is correct.
by KHuang1L
Sat Oct 13, 2018 9:22 pm
Forum: Balancing Chemical Reactions
Topic: How To....
Replies: 16
Views: 468

Re: How To....

I like to begin by writing down all the elements and how many atoms there are in each side first, starting with elements in fewer molecules. Looking at those numbers, I add stoichiometric coefficients to balance the two sides.
by KHuang1L
Wed Oct 03, 2018 5:17 pm
Forum: Administrative Questions and Class Announcements
Topic: Bruincast
Replies: 2
Views: 73

Re: Bruincast

His lectures often go over the video modules, so you can also watch those.
by KHuang1L
Wed Oct 03, 2018 5:16 pm
Forum: Administrative Questions and Class Announcements
Topic: UA Office Hours [ENDORSED]
Replies: 3
Views: 69

Re: UA Office Hours [ENDORSED]

UA Office Hours are posted under "Peer Learning Sessions and Step-Up Program" in the class website.
by KHuang1L
Wed Oct 03, 2018 5:14 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Molecule vs Formula Unit
Replies: 4
Views: 66

Re: Molecule vs Formula Unit

Molecules and formula units are not interchangeable. Formula units are used to describe ions in ionic compounds.

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