Search found 60 matches
- Sun Mar 17, 2019 4:29 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Bimolecular
- Replies: 13
- Views: 2172
Re: Bimolecular
Bimolecular means there are two species involved in the elementary step.
- Sun Mar 17, 2019 4:29 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Activation Energy
- Replies: 16
- Views: 1416
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.
- Sun Mar 17, 2019 4:27 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Rate Determining Step
- Replies: 9
- Views: 1075
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.
- Sun Mar 10, 2019 11:50 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: how is kinetics different?
- Replies: 17
- Views: 1591
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.
- 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: 794
Re: Log version vs ln Version
It does not matter. But using log is more convenient when calculating for pH.
- Sun Mar 10, 2019 11:44 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: K Value
- Replies: 7
- Views: 722
Re: K Value
Should be specific to the question
- 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: 403
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.
- 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: 260
Re: 7th edition 6M.5
It could just be a typo.
- 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: 582
Re: H+ in cell diagrams
Include H+ in the cell diagram when it participates in the half reactions.
- Sun Feb 24, 2019 12:32 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidating/Reducing AGENTS
- Replies: 6
- Views: 712
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.
- Sun Feb 24, 2019 12:31 pm
- Forum: Balancing Redox Reactions
- Topic: Test 2 Material
- Replies: 11
- Views: 882
Re: Test 2 Material
Material after the midterm up to week 7 material.
- Sun Feb 24, 2019 12:29 pm
- Forum: Balancing Redox Reactions
- Topic: difference between oxidation and reduction
- Replies: 8
- Views: 913
Re: difference between oxidation and reduction
Oxidation is the removing of electrons and reduction is the addition of electrons.
- Sat Feb 16, 2019 12:22 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Equation based on equilibrium
- Replies: 5
- Views: 473
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.
- Sat Feb 16, 2019 12:19 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs free energy
- Replies: 7
- Views: 668
Re: Gibbs free energy
The reaction is spontaneous when delta G is negative and not spontaneous when delta G is positive.
- Sat Feb 16, 2019 12:18 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: gibbs free energy
- Replies: 10
- Views: 856
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.
- Sun Feb 10, 2019 7:57 pm
- Forum: Calculating Work of Expansion
- Topic: Conversions to joules?
- Replies: 4
- Views: 751
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.
- Sun Feb 10, 2019 7:55 pm
- Forum: Calculating Work of Expansion
- Topic: Units
- Replies: 7
- Views: 681
Re: Units
The formula sheet has unit conversion equations to get to J.
- Sun Feb 10, 2019 7:54 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible vs Irreversible
- Replies: 9
- Views: 799
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).
- Fri Feb 01, 2019 9:32 pm
- Forum: Phase Changes & Related Calculations
- Topic: Week 4 Homework
- Replies: 12
- Views: 1192
Re: Week 4 Homework
Anything from what we learned in week 3 and week 4.
- Fri Feb 01, 2019 9:32 pm
- Forum: Phase Changes & Related Calculations
- Topic: What Does U and q stand for?
- Replies: 9
- Views: 2244
Re: What Does U and q stand for?
U is internal energy and q is heat
- Fri Feb 01, 2019 9:31 pm
- Forum: Phase Changes & Related Calculations
- Topic: Test #1
- Replies: 11
- Views: 908
Re: Test #1
Yes
- Sat Jan 26, 2019 5:26 pm
- Forum: Phase Changes & Related Calculations
- Topic: Enthalpy and States
- Replies: 8
- Views: 749
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.
- Sat Jan 26, 2019 5:25 pm
- Forum: Phase Changes & Related Calculations
- Topic: Modules
- Replies: 17
- Views: 1231
Re: Modules
No, but they are good practice.
- Sat Jan 26, 2019 5:24 pm
- Forum: Phase Changes & Related Calculations
- Topic: Why steam causes severe burns
- Replies: 9
- Views: 1928
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).
- Sat Jan 19, 2019 12:41 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: When is X negligible.
- Replies: 6
- Views: 512
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.
- Sat Jan 19, 2019 12:38 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Gibbs Free Energy
- Replies: 1
- Views: 110
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.
- Sat Jan 19, 2019 12:34 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Endothermic
- Replies: 6
- Views: 586
Re: Endothermic
Heat is required in endothermic reactions, so adding heat will further the reaction.
- Fri Jan 11, 2019 4:32 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q and K
- Replies: 13
- Views: 1226
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.
- Fri Jan 11, 2019 4:30 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kp
- Replies: 9
- Views: 729
Re: Kp
The question should specify whether to solve for Kp or Kc.
- Thu Jan 10, 2019 8:36 pm
- Forum: Ideal Gases
- Topic: Q and K [ENDORSED]
- Replies: 35
- Views: 3004
Re: Q and K [ENDORSED]
Same formulas but they calculate for different things
- Sat Dec 08, 2018 11:15 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentate
- Replies: 11
- Views: 1099
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.
- Sat Dec 08, 2018 11:13 am
- Forum: Biological Examples
- Topic: Ligands
- Replies: 7
- Views: 857
Re: Ligands
The central atom should be the transition metal.
- Sat Dec 08, 2018 11:12 am
- Forum: Naming
- Topic: Final Exam
- Replies: 9
- Views: 829
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.
- Sat Dec 01, 2018 4:14 pm
- Forum: Hybridization
- Topic: Hybridization Notation
- Replies: 10
- Views: 866
Re: Hybridization Notation
The examples in class had sp3d.
- Sat Dec 01, 2018 4:13 pm
- Forum: Hybridization
- Topic: Pi bonds in triple bond
- Replies: 17
- Views: 1755
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.
- Sat Dec 01, 2018 4:11 pm
- Forum: Hybridization
- Topic: CH2O hybridization
- Replies: 9
- Views: 15220
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.
- Mon Nov 19, 2018 11:01 pm
- Forum: Ionic & Covalent Bonds
- Topic: delta positive delta negative
- Replies: 15
- Views: 2236
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.
- Mon Nov 19, 2018 10:59 pm
- Forum: Lewis Structures
- Topic: Boron Trifluoride
- Replies: 8
- Views: 792
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.
- Mon Nov 19, 2018 10:55 pm
- Forum: Lewis Structures
- Topic: Polar vs Nonpolar molecules
- Replies: 7
- Views: 849
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.
- Sat Nov 17, 2018 10:32 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Single Regions?
- Replies: 8
- Views: 754
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.
- Sat Nov 17, 2018 10:30 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: tetrahedral vs trigonal planar
- Replies: 9
- Views: 1059
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.
- Sat Nov 17, 2018 10:28 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Distance from Central Atom
- Replies: 8
- Views: 555
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.
- Tue Nov 06, 2018 4:34 pm
- Forum: Octet Exceptions
- Topic: Octet Exceptions
- Replies: 3
- Views: 306
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.
- Tue Nov 06, 2018 4:31 pm
- Forum: Resonance Structures
- Topic: Bond Lengths
- Replies: 7
- Views: 1967
Re: Bond Lengths
The bond length for each N-O bond is an average of the bond lengths for all three resonance hybrids.
- Tue Nov 06, 2018 4:30 pm
- Forum: Resonance Structures
- Topic: Most Stable Configuration
- Replies: 11
- Views: 1156
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...
- Tue Oct 30, 2018 3:31 pm
- Forum: Einstein Equation
- Topic: Number of photons
- Replies: 7
- Views: 1076
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.
- Tue Oct 30, 2018 3:30 pm
- Forum: DeBroglie Equation
- Topic: De Broglie
- Replies: 12
- Views: 1390
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.
- Tue Oct 30, 2018 3:28 pm
- Forum: Lewis Structures
- Topic: Dots in Lewis Stucture
- Replies: 14
- Views: 1168
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.
- Sat Oct 27, 2018 10:54 am
- Forum: Einstein Equation
- Topic: E=hv [ENDORSED]
- Replies: 52
- Views: 18031
Re: E=hv [ENDORSED]
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 ...
- Sat Oct 27, 2018 10:50 am
- Forum: Photoelectric Effect
- Topic: Conditions that allow electron to be ejected from metal surface
- Replies: 12
- Views: 2116
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...
- Sat Oct 27, 2018 10:47 am
- Forum: Properties of Light
- Topic: Is light in waves or photons?
- Replies: 10
- Views: 901
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.
- Fri Oct 19, 2018 5:01 pm
- Forum: Photoelectric Effect
- Topic: Threshold energy [ENDORSED]
- Replies: 17
- Views: 2074
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.
- Fri Oct 19, 2018 4:54 pm
- Forum: Properties of Light
- Topic: Do I have to memorize the spectrum?
- Replies: 20
- Views: 1564
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.
- Fri Oct 19, 2018 4:53 pm
- Forum: Properties of Light
- Topic: Test 2 [ENDORSED]
- Replies: 15
- Views: 1177
Re: Test 2 [ENDORSED]
Everything we learned last week up to today's lecture.
- Sat Oct 13, 2018 9:28 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Number of questions on test one [ENDORSED]
- Replies: 39
- Views: 21460
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.
- Sat Oct 13, 2018 9:23 pm
- Forum: Empirical & Molecular Formulas
- Topic: Going from empirical to Molecular formula
- Replies: 14
- Views: 2094
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.
- Sat Oct 13, 2018 9:22 pm
- Forum: Balancing Chemical Reactions
- Topic: How To....
- Replies: 16
- Views: 2537
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.
- Wed Oct 03, 2018 5:17 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Bruincast
- Replies: 2
- Views: 273
Re: Bruincast
His lectures often go over the video modules, so you can also watch those.
- Wed Oct 03, 2018 5:16 pm
- Forum: Administrative Questions and Class Announcements
- Topic: UA Office Hours [ENDORSED]
- Replies: 3
- Views: 270
Re: UA Office Hours [ENDORSED]
UA Office Hours are posted under "Peer Learning Sessions and Step-Up Program" in the class website.
- Wed Oct 03, 2018 5:14 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Molecule vs Formula Unit
- Replies: 4
- Views: 796
Re: Molecule vs Formula Unit
Molecules and formula units are not interchangeable. Formula units are used to describe ions in ionic compounds.