Search found 62 matches
- Fri Mar 15, 2019 10:27 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Concentration Cells
- Replies: 1
- Views: 235
Concentration Cells
What will we be required to know about concentration cells?
- Fri Mar 15, 2019 10:25 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: K Constant
- Replies: 1
- Views: 243
K Constant
Why does the equilibrium constant K equal the ratio of the forward and reverse rate constants?
- Fri Mar 15, 2019 10:23 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isometric/Isochoric
- Replies: 11
- Views: 1339
Re: Isometric/Isochoric
Yes, a bomb calorimeter maintains a constant volume (isochoric) for reactions.
- Mon Mar 11, 2019 2:16 am
- Forum: Second Order Reactions
- Topic: 2nd order
- Replies: 4
- Views: 525
Re: 2nd order
The y-axis is the inverse of the concentration of A. Thus, the slope shows that as time increases, the inverse of [A] increases (not [A] itself).
- Mon Mar 11, 2019 2:14 am
- Forum: Zero Order Reactions
- Topic: Zero Order Reactions
- Replies: 8
- Views: 1003
Re: Zero Order Reactions
Different order reactions have different reaction mechanisms, or the number of steps to form the product.
- Mon Mar 11, 2019 2:12 am
- Forum: General Rate Laws
- Topic: Order of rxns and stoichiometric coefficients
- Replies: 3
- Views: 340
Re: Order of rxns and stoichiometric coefficients
They are not necessarily the same, but in some occasions they are. It is best not to assume they are the same and to find the order itself.
- Sun Mar 03, 2019 8:49 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: pH at 10 C
- Replies: 3
- Views: 377
Re: pH at 10 C
I think it depends on the test version you had, but if you used the Van't Hoff equation and used the equilibrium constant equation to then convert [H+] to a pH value, you should get the right answer.
- Sun Mar 03, 2019 8:43 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: negative n?
- Replies: 2
- Views: 280
Re: negative n?
If you are referring to the exponent n in the rate law, then I do believe it can be a negative value. This would be when the increase of the concentration of a reactant causes the rate of the reaction to decrease.
- Sun Mar 03, 2019 8:39 am
- Forum: General Rate Laws
- Topic: Overall sum
- Replies: 7
- Views: 752
Re: Overall sum
The overall order of a reaction is the total sum of the orders of all the reactants.
- Sun Feb 24, 2019 1:20 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: test 3
- Replies: 10
- Views: 954
Re: test 3
Does anyone know if it will also include entropy and previous thermodynamic concepts?
- Sun Feb 24, 2019 1:17 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell diagram
- Replies: 3
- Views: 369
Re: Cell diagram
I think it's safe to say the anode is on the left and the cathode is on the right because that's how it was presented in the lectures. The standard reaction potentials are given as reductions, so which ever one is being oxidized in the actual reaction, needs to be reversed.
- Sun Feb 24, 2019 1:12 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cell Diagram
- Replies: 6
- Views: 537
Re: Galvanic Cell Diagram
I think it would be best to have an understanding of how it works. Knowing that, drawing the diagram should come easier.
- Mon Feb 18, 2019 9:56 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy vs. Standard Gibbs Free Energy
- Replies: 3
- Views: 378
Re: Gibbs Free Energy vs. Standard Gibbs Free Energy
The standard Gibbs Free Energy is fixed for a certain reaction and temperature. It is also under standard conditions and the difference between the Gibbs free energy of pure products and reactants.
- Mon Feb 18, 2019 9:51 am
- Forum: Calculating Work of Expansion
- Topic: Units for R
- Replies: 10
- Views: 1334
Re: Units for R
There are different values for the constant R depending on the units used in the problem.
- Mon Feb 18, 2019 9:50 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: When does delta U equal zero?
- Replies: 17
- Views: 8215
Re: When does delta U equal zero?
This is for an isothermal reaction. (We can also infer from this that q=-w)
- Sun Feb 10, 2019 12:50 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta U
- Replies: 8
- Views: 848
Re: Delta U
The internal energy is zero when it is a reversible reaction or if it is at a constant temperature.
- Sun Feb 10, 2019 12:47 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: adding an inert gas
- Replies: 4
- Views: 628
Re: adding an inert gas
They do not affect the concentrations of other substances in equilibrium because they do not react.
- Sun Feb 10, 2019 12:43 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Enthalpy Equations
- Replies: 1
- Views: 262
Enthalpy Equations
Can someone explain when and why we use 3/2 R and 5/2 R as the Cv value when finding enthalpy?
- Sat Feb 02, 2019 6:04 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta U
- Replies: 4
- Views: 444
Delta U
If U is a state function, how is it that we can use work, which is pathway-dependent, to calculate it?
- Sat Feb 02, 2019 5:56 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Review
- Replies: 14
- Views: 1174
Re: Midterm Review
For Chem 14A last quarter Lavelle did have review sessions led by TAs and UAs the week leading up to the Midterm, so I would think that would be the case this quarter too?
- Sat Feb 02, 2019 5:54 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Problem 8.1 (c) 6th edition
- Replies: 2
- Views: 391
Problem 8.1 (c) 6th edition
Why is "coolant in a refrigerator coil" considered an isolated system? I am not familiar with the contraptions inside a refrigerator, so I am just wondering.
- Sun Jan 27, 2019 1:30 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: The 3 methods
- Replies: 5
- Views: 491
Re: The 3 methods
I believe that it depends on the type of information given in the problem. However, I recall Dr. Lavelle saying that Method 1 would give the most reliable and accurate answer.
- Sun Jan 27, 2019 1:27 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Heat vs Enthalpy
- Replies: 4
- Views: 327
Heat vs Enthalpy
Are heat and enthalpy considered the same thing, or are there any differences between them?
- Sun Jan 27, 2019 1:25 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Work, state property
- Replies: 3
- Views: 342
Re: Work, state property
You would need to know the energy expenditure for each step of the reaction to get the total amount of work versus just calculating the net change when finding enthalpy.
- Sun Jan 20, 2019 12:50 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium Constant
- Replies: 2
- Views: 3014
Re: Equilibrium Constant
If K>1 then there are more products at equilibrium. If K<1 then there are more reactants. If K=1 then there are equal amounts of reactants and products at equilibrium.
- Sun Jan 20, 2019 12:35 pm
- Forum: Ideal Gases
- Topic: ice
- Replies: 4
- Views: 546
Re: ice
There is no difference within the ICE table itself, just the type of species that are put into it.
- Sun Jan 20, 2019 12:19 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Salt in the Equation
- Replies: 1
- Views: 254
Re: Salt in the Equation
In lecture Dr. Lavelle stated that all Group 1 and MOST Group 2 salts do not affect the pH of a solution. However, he did not state specifically which ones do not, so I do not think that is something we are required to know.
- Fri Jan 11, 2019 9:00 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Changing Pressure
- Replies: 6
- Views: 525
Changing Pressure
Can someone clarify why there needs to be a change in volume for there to be a change in pressure of a reaction in equilibrium?
- Fri Jan 11, 2019 8:49 pm
- Forum: Ideal Gases
- Topic: Ideal Gases
- Replies: 7
- Views: 484
Re: Ideal Gases
I believe the general assumption is that a gas acts more "ideal" at higher temperatures and at lower pressures. I think most of the problems we will be given deal with ideal gases unless otherwise stated.
- Fri Jan 11, 2019 8:46 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc and Kp
- Replies: 12
- Views: 1661
Re: Kc and Kp
We use Kp for gases, and it is calculated by using the partial pressures of those gases, so I don't believe this would apply to solids or liquids.
- Thu Dec 06, 2018 7:01 pm
- Forum: Lewis Acids & Bases
- Topic: Ligands
- Replies: 7
- Views: 887
Re: Ligands
A neutral ligand contributes no charge to the coordination compound. An example would be H20 (aqua) or NH3 (ammine).
Re: K3[CoF6]
I believe this is because Co is the transition metal cation and F is considered the ligand in this case.
- Sun Dec 02, 2018 8:35 pm
- Forum: Naming
- Topic: Polydentate Ligands
- Replies: 2
- Views: 313
Re: Polydentate Ligands
A polydentate ligand has multiple binding sites that donate multiple electron pairs. You can look for and count the two dots denoting lone pairs as a sign.
Re: water
The molecules are normally written in an order where the atom with the lone pair is right next to the atom that receives it. Thus, because oxygen has the lone pairs in a H20 molecule, you would write it 0H2 if the atom that receives the electrons is to the left of the water molecule (such as when dr...
- Fri Nov 23, 2018 11:45 pm
- Forum: Electronegativity
- Topic: Nonmetals?
- Replies: 6
- Views: 704
Re: Nonmetals?
Yes, generally non-metals tend to be more electronegative than metals, as the non-metals are located on the right side of the periodic table (and from the periodic trends, we know that from left to right electronegativity increases.)
- Fri Nov 23, 2018 11:40 pm
- Forum: Electronegativity
- Topic: Largest Electronegativity
- Replies: 4
- Views: 419
Re: Largest Electronegativity
Fluorine is the most electronegative atom on the periodic table.
- Fri Nov 23, 2018 11:37 pm
- Forum: Hybridization
- Topic: double bonds
- Replies: 14
- Views: 1128
Re: double bonds
A double bond consists of one sigma and one pi bond. (Sigma and pi bonds are different because of the different orientation of the orbitals of the bond.)
- Sun Nov 18, 2018 6:27 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: molecular shape and bond angles
- Replies: 3
- Views: 367
Re: molecular shape and bond angles
I think we just need to know the angles for the basic geometry (electron density geometry) because those values are known and consistent I believe (like 90, 120, 180 degrees). For the electron density geometry, I think we just need to know how the lone pairs affect the bond angles.
- Sun Nov 18, 2018 6:19 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chem Community Posts
- Replies: 3
- Views: 410
Re: Chem Community Posts
My TA told us that posts were cumulative, and thus built up and counted at the end. So, just in case we miss a week or something we could make it up. I am not completely sure if this is the case with all TAs though.
- Sun Nov 18, 2018 6:16 pm
- Forum: Dipole Moments
- Topic: Dipole moments in terms of very electronegative atoms
- Replies: 3
- Views: 449
Re: Dipole moments in terms of very electronegative atoms
Because the dipole moments are not symmetrically distributed and are different strengths, there would be a net dipole moment, thus making it polar.
- Sun Nov 18, 2018 6:14 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular Geometry
- Replies: 6
- Views: 594
Re: Molecular Geometry
The electron density geometry does take into account all the bonding and lone pairs linked to the central atom. Molecular geometry only takes into account of the bonds that are actually attached to other molecules. If there are no lone pairs, these shapes are the same.
- Sat Nov 10, 2018 2:44 pm
- Forum: Bond Lengths & Energies
- Topic: MIDTERM Bond Length Question
- Replies: 15
- Views: 1525
Re: MIDTERM Bond Length Question
There were resonance structures for the molecule that included single and double bonds, so the actual molecule would have an average of those two bonds. I took the average of the two lengths and got 130pm.
- Sat Nov 10, 2018 2:31 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Naming the shape
- Replies: 6
- Views: 622
Re: Naming the shape
There are also other names of shapes when there are lone pairs such as bent, T-shaped, see-saw, etc.
- Sat Nov 10, 2018 2:23 pm
- Forum: Electronegativity
- Topic: Electron Affinity
- Replies: 3
- Views: 869
Electron Affinity
Would a neutral K atom or K+ ion have a more negative value of electron affinity and why?
- Sat Nov 03, 2018 9:33 pm
- Forum: Lewis Structures
- Topic: Brackets around ions
- Replies: 2
- Views: 156
Re: Brackets around ions
I am not sure why that is, but during the TA review sessions, they mentioned that you should put brackets around ions when completing their Lewis structure.
- Sat Nov 03, 2018 9:28 pm
- Forum: Trends in The Periodic Table
- Topic: Exceptions to ionization energy
- Replies: 1
- Views: 300
Re: Exceptions to ionization energy
The concept basically follows that having a half or full filled subshell is more stable for an atom. Regarding electron affinity, N would have a lower E.A. than expected because it doesn't want to gain another electron due to the fact that it already has a half filled 2p subshell. Carbon, on the oth...
- Sat Nov 03, 2018 9:22 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic character [ENDORSED]
- Replies: 5
- Views: 606
Re: Ionic character [ENDORSED]
If you look up the electronegativity values of H, C, and F, they are 2.1, 2.5, and 4.0 respectively. So, the electronegativity values for Carbon and Hydrogen are a lot closer than the value for Fluorine. Just because they appear closer on the periodic table doesn't necessarily mean their values are ...
- Sun Oct 28, 2018 2:48 pm
- Forum: Trends in The Periodic Table
- Topic: Removing 2nd e- [ENDORSED]
- Replies: 4
- Views: 422
Re: Removing 2nd e- [ENDORSED]
If you remove an electron, you are creating a cation. This net positive charge creates a stronger electrostatic attraction that holds the electrons tighter to the nucleus, thus requiring more energy to separate.
- Sun Oct 28, 2018 2:43 pm
- Forum: Ionic & Covalent Bonds
- Topic: ionic vs. covalent bonds
- Replies: 3
- Views: 358
Re: ionic vs. covalent bonds
This depends on the environment because in an aqueous solution covalent bonds would be stronger as ionic bonds would beak and separate due to the polar characteristics of water. However, ionic bonds out of water would be stronger due to the attraction of opposite charges.
- Sun Oct 28, 2018 2:39 pm
- Forum: Lewis Structures
- Topic: Lewis Structure Drawing
- Replies: 6
- Views: 483
Lewis Structure Drawing
In high school I remember being allowed to draw straight lines whenever there were two valence electrons on a Lewis structure diagram, as a kind of shorthand method instead of drawing all dots. However, in lecture we learned to use straight lines only for shared electrons. Is the other way incorrect?
- Sun Oct 21, 2018 9:46 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Particle Size
- Replies: 3
- Views: 347
Re: Particle Size
It was not said exactly if there have been experiments done on this. However, I would think that anything at the atomic level would be affected by the light source.
- Sun Oct 21, 2018 9:33 pm
- Forum: Photoelectric Effect
- Topic: Visible Light Spectrum
- Replies: 6
- Views: 521
Re: Visible Light Spectrum
I believe in lecture Dr. Lavelle said it is safe to assume the visible light spectrum range is from about 400 to 700nm.
- Sun Oct 21, 2018 9:19 pm
- Forum: Properties of Light
- Topic: Using a rounded speed of light in EM problems
- Replies: 4
- Views: 660
Re: Using a rounded speed of light in EM problems
If the speed of light was given at 2.998 x 10^8 and you want to round it, I would use 3.000 x 10^8 because it has the same amount of sig figs but would require less digits to input in the calculator. Using that value with 4 sig figs and given a value 2.55 nm with 3 sig figs, your answer should have ...
- Sun Oct 21, 2018 9:07 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Electron Spin
- Replies: 3
- Views: 405
Electron Spin
I know the electron spin, or ms quantum number, is used because every electron had their own unique set of quantum numbers, but why is it +1/2 and -1/2? Was the value of 1/2 arbitrary?
- Sun Oct 21, 2018 9:03 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Atomic Orbitals
- Replies: 3
- Views: 225
Re: Atomic Orbitals
The s, p,d,and f orbitals correspond to the main types of shapes of the atomic orbitals. For example, the s orbitals are in the shape of a sphere and the p orbitals are two lobes with a nodal plane through the center. The periodic table is also split up in to s, p, d, and f blocks in which the valen...
- Sun Oct 14, 2018 12:19 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: n Quantum Number
- Replies: 1
- Views: 146
n Quantum Number
In the equations involving n, I know its value has to be a whole integer. In the book, it's followed by an ellipsis, implying that the value continues forever. Is there a certain value of n that becomes unreasonable?
- Sun Oct 14, 2018 11:57 am
- Forum: Properties of Light
- Topic: Speed of Light
- Replies: 41
- Views: 2699
Re: Speed of Light
I did some research behind it, and some sources are claiming that recent studies show light doesn't always travel at the speed proposed by Einstein's theory. However, for the purposes of this class the speed of light is assumed to be constant.
- Sun Oct 14, 2018 11:52 am
- Forum: Photoelectric Effect
- Topic: 1B.15 Part C
- Replies: 2
- Views: 177
Re: 1B.15 Part C
I don't see a question 1B.15 in the textbook. Is it at the end of the chapter?
- Thu Oct 11, 2018 8:44 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: H-Atom Emperical Equation
- Replies: 2
- Views: 202
H-Atom Emperical Equation
We learned in class that the equation E{n}= -(hR)/n^2 was only used for Hydrogen atoms because it was based on experimental data, but how different would an empirical equation like this be for other atoms?
- Thu Oct 04, 2018 8:46 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: HW #L 11
- Replies: 1
- Views: 170
Re: HW #L 11
When something is neutralized, water is formed. So, taking the reactants of that second equation, Mg(OH)2 and HCl, you would have H2O as a product. This would be formed from the OH- in the Mg(OH)2 and the H+ from the HCl. Then, the remaining Mg2- and Cl- ions would form a compound, MgCl2. Once you h...
- Thu Oct 04, 2018 8:20 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Homework help G21
- Replies: 2
- Views: 285
Re: Homework help G21
43123230_162077154732160_7899198701413859328_n.jpg 43102606_2120414714877915_907926004423458816_n.jpg I did the work for the problem step by step. To solve it you need to know that the compounds given dissolve and break up into ions. The answer was 0.01 off from the textbook solution mostly likely ...
- Thu Oct 04, 2018 7:55 pm
- Forum: SI Units, Unit Conversions
- Topic: HW E9 in textbook
- Replies: 3
- Views: 351
Re: HW E9 in textbook
A mole is 6.022 x 10^23 units of something, whether it be particles, atoms, molecules, etc. So, for example, there should be 6.022 x 10^23 separate water molecules in one mole of H20. The characteristic that differentiates moles of different particles would be their mass.