Search found 62 matches
- Thu Mar 14, 2019 8:30 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Intermediate vs catalyst
- Replies: 8
- Views: 853
Re: Intermediate vs catalyst
Catalysts appear as a reactant for the first step of the reaction mechanism, while intermediates are formed during the reaction. They are both left out of the overall equation of the reaction.
- Thu Mar 14, 2019 8:23 pm
- Forum: Second Order Reactions
- Topic: Hmwrk 15.39
- Replies: 1
- Views: 534
Re: Hmwrk 15.39
To my understanding, the question could have just told us that "k = 0.015 L mol-1 min-1 for the rate law of this reaction", and that would not change how you should approach the problem.
- Wed Mar 13, 2019 2:09 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final Questions
- Replies: 10
- Views: 1221
Re: Final Questions
It will be 8 questions just like the midterm, but there will be more small parts to each of them.
- Sun Mar 10, 2019 8:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Midterm
- Replies: 5
- Views: 556
Re: Midterm
A large K suggests that the forward reaction is favored. This means that the products are relatively more stable compared to the reactants because the reactants will have a tendency to split/change.
- Sun Mar 10, 2019 8:22 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: What does K say about stability?
- Replies: 5
- Views: 3581
Re: What does K say about stability?
To my understanding, a large K tells us that the forward reaction is favored. This means that the reactants have a tendency to split and/or change, making them unstable. Therefore, the products are relatively stable when compared to the reactants.
- Sun Mar 10, 2019 8:11 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Final Exam
- Replies: 23
- Views: 1831
Re: Final Exam
Because this class is cumulative, chem equilibrium will definely show up in a problem or two on the final
- Thu Feb 28, 2019 7:08 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Organization of cell diagrams
- Replies: 9
- Views: 855
Re: Organization of cell diagrams
You will need it in the absence of solid for either of the half reactions
- Thu Feb 28, 2019 7:03 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: H+, OH-, water
- Replies: 9
- Views: 944
Re: H+, OH-, water
You will only need to include H+ and OH-.
- Thu Feb 28, 2019 6:34 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 11.17
- Replies: 3
- Views: 518
Re: 11.17
Going further with the directions that is provided, you can calculate ΔG^(o) with the K given to you through -RTln(K).
- Sun Feb 24, 2019 1:27 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free energy
- Replies: 5
- Views: 605
Re: Gibbs Free energy
When it's not given, it is usually suggested to be 298K.
- Sun Feb 24, 2019 1:24 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneity
- Replies: 8
- Views: 826
Re: Spontaneity
I believe that the reaction is at equilibrium if delta G is zero.
- Sun Feb 24, 2019 1:22 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Test 3
- Replies: 14
- Views: 2354
Re: Test 3
^To add on to the previous comment, we only need to study electrochemistry material up to what we went over in lecture on Friday.
- Sun Feb 17, 2019 1:11 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: ΔU = 0?
- Replies: 4
- Views: 1016
Re: ΔU = 0?
Delta U=0 assumes an isothermal process because of delta U=(3/2)nR(delta T). When delta U is zero, delta T will have to be zero as well for the equation to be true.
- Sun Feb 17, 2019 1:07 am
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: How to calculate W
- Replies: 9
- Views: 1470
Re: How to calculate W
(# of mircostates)^(# of molecules)
- Sun Feb 17, 2019 12:56 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Midterm Grades
- Replies: 35
- Views: 2798
Re: Midterm Grades
Last quarter, they gave it back in lectures 1 week after we took the midterm.
- Sat Feb 09, 2019 5:51 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Midterm [ENDORSED]
- Replies: 49
- Views: 4936
Re: Midterm [ENDORSED]
In my opinion, the best way to prepare is doing the practice midterms that are given out during review sessions.
- Sat Feb 09, 2019 5:44 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: deltaS=nCvln(t2/t1) what is Cv?
- Replies: 7
- Views: 2830
Re: deltaS=nCvln(t2/t1) what is Cv?
Cv is the heat capacity of the system when the volume is constant.
- Sat Feb 09, 2019 5:41 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: If not Gibbs Free Energy then what is the last topic for midterm?
- Replies: 4
- Views: 451
Re: If not Gibbs Free Energy then what is the last topic for midterm?
The topics tested on the midterm should cover everything about entropy up until the introduction of Gibbs free energy. According to the textbook, the last topic for midterm is the entropy of surroundings.
- Fri Feb 01, 2019 1:37 pm
- Forum: Phase Changes & Related Calculations
- Topic: J vs. kJ
- Replies: 9
- Views: 1098
Re: J vs. kJ
J is what is most commonly used to represent work. We can of course use kJ to represent work as well when specified by the problem.
- Fri Feb 01, 2019 1:32 pm
- Forum: Phase Changes & Related Calculations
- Topic: U and its relations to work
- Replies: 8
- Views: 838
Re: U and its relations to work
U represents the internal energy of a system. Its relation to work can be seen in the first law of thermodynamics: change in U = q(heat exchanged) + w(work done on or by the system).
- Fri Feb 01, 2019 1:19 pm
- Forum: Calculating Work of Expansion
- Topic: Work
- Replies: 5
- Views: 571
Re: Work
I believe that the main things to consider about work in thermodynamics are that negative work is done onto the system(compression of gas) and that positive work is done by the system(expansion of gas).
- Sat Jan 26, 2019 2:41 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: pH
- Replies: 9
- Views: 1092
Re: pH
pH tells us how acidic or basic something is. We can find pH through -log([H+]). We can also find pH if we only have pOH(log([OH-])) using the relationship pH+pOH=14.
- Sat Jan 26, 2019 2:30 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Ka
- Replies: 6
- Views: 691
Re: Ka
Because H2SO4 is a strong acid, it will not have a Ka value because it completely dissociates into H and HSO4 when it first loses the hydrogen.
- Sat Jan 26, 2019 2:17 pm
- Forum: Ideal Gases
- Topic: kc vs kp
- Replies: 19
- Views: 3513
Re: kc vs kp
You can really only use kc in place of kp when all of the compounds involved in the reaction are in the gaseous phase.
- Sun Jan 20, 2019 7:22 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ka and Kb as Inverses?
- Replies: 7
- Views: 1887
Re: Ka and Kb as Inverses?
I don't believe I have ever seen Ka and Kb sharing an inverse relationship from the doing the textbook problems. I believe the only relevant relationship is Ka x Kb = Kw.
- Sun Jan 20, 2019 7:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Concentrations Effect on K
- Replies: 8
- Views: 554
Re: Concentrations Effect on K
K will not change if the concentrations of both the reactants and the products change by the same amount. This is the case because their ratio would remain the same.
- Sun Jan 20, 2019 7:13 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Kw
- Replies: 6
- Views: 590
Re: Kw
Yes, the concentration of hydronium and hydroxide are equal in pure(neutral) water.
- Fri Jan 11, 2019 1:33 pm
- Forum: Ideal Gases
- Topic: What does K represent?
- Replies: 9
- Views: 2553
Re: What does K represent?
K is the equilibrium constant. It represents the ratio of the concentration of products to the concentration of reactants in a reaction that tells us when the rate of forward reaction and the rate of reverse reaction are equal.
- Fri Jan 11, 2019 1:16 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: defining Q
- Replies: 6
- Views: 594
Re: defining Q
When Q is smaller than K, it suggests that there is greater concentration of reactants and less concentration of products than suggested at equilibrium. Therefore, the reaction will take a forward direction to lower the concentration of reactants and increase the concentration of products until Q=K.
- Fri Jan 11, 2019 1:07 pm
- Forum: Ideal Gases
- Topic: Q and K [ENDORSED]
- Replies: 35
- Views: 3199
Re: Q and K [ENDORSED]
The formulas for both Q and K are the same. K specifically tells us when the reaction is at equilibrium. Q can be be found during any instance of the reaction in order to determine which direction the reaction is going when it is compared to K.
- Fri Dec 07, 2018 7:12 pm
- Forum: Dipole Moments
- Topic: Dipole dipole moments
- Replies: 3
- Views: 652
Re: Dipole dipole moments
There is no dipole-dipole interaction as the net dipole moment is zero.
- Fri Dec 07, 2018 7:10 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs
- Replies: 5
- Views: 553
Re: Lone Pairs
The only things that affect the shape of a molecule are the central atom's lone pairs and the bonds it formed.
- Fri Dec 07, 2018 7:05 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Correct Bond Angles
- Replies: 6
- Views: 680
Re: Correct Bond Angles
There will always be a slight difference because of the unique properties of molecules that affect their interactions.
- Thu Nov 29, 2018 5:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: AX2E2
- Replies: 14
- Views: 4591
Re: AX2E2
The VESPR formula AX2E2 suggests that the shape of the molecule is bent/angular, which means that the bond angles are less than 109.5 degrees.
- Wed Nov 28, 2018 10:07 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polarity
- Replies: 5
- Views: 641
Re: Polarity
Just as you mentioned, NO2 is polar because of the bent shape of the atoms as it prevents the dipole moments from canceling out.
- Wed Nov 28, 2018 1:24 pm
- Forum: Dipole Moments
- Topic: 4.29
- Replies: 3
- Views: 197
Re: 4.29
I would always like to look at dipole moments as vectors. Looking at option 1, adding the two vectors (dipole moments) together gives us a resultant vector with a larger magnitude than the resultant vector for option 2.
- Sat Nov 24, 2018 4:57 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: double and triple bonds
- Replies: 10
- Views: 1136
Re: double and triple bonds
We treat double bonds and triple bonds like they are a single bond with one region of electron density in the VESPR model.
- Sat Nov 24, 2018 4:55 pm
- Forum: Hybridization
- Topic: Writing out Hybridization
- Replies: 8
- Views: 602
Re: Writing out Hybridization
Either way is fine. It's just whether or not you prefer using sp^3d to follow the order of increasing energy of orbitals as we did for electron configurations.
- Sat Nov 24, 2018 4:48 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: How to state bond angles.
- Replies: 7
- Views: 774
Re: How to state bond angles.
I believe just putting "less than 109.5 degrees" is fine for all bond angles around 100-109 degrees.
- Sun Nov 18, 2018 10:00 pm
- Forum: Student Social/Study Group
- Topic: Turning in Homework (Thanksgiving Break)
- Replies: 8
- Views: 855
Re: Turning in Homework (Thanksgiving Break)
We just have to turn in 14 homework problems during week 9 to make up for missing week 8 discussion section.
- Sun Nov 18, 2018 9:16 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: Intermolecular Forces
- Replies: 7
- Views: 1426
Re: Intermolecular Forces
I believe the main difference to know is that London forces occur in all molecules while dipole-dipole forces only occur in polar molecules.
- Sun Nov 18, 2018 9:03 pm
- Forum: Dipole Moments
- Topic: Test
- Replies: 15
- Views: 1328
Re: Test
It starts right after Thanksgiving break, which is great because more time to study!
- Sat Nov 10, 2018 6:53 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg equation
- Replies: 3
- Views: 849
Re: Rydberg equation
Given that the energy is found through -(hR/n^2), increasing n would indicate greater energy as the result becomes less negative. If we use hR/n^2 to find the energy instead, increasing n would result in lower energy values, which is not correct.
- Sat Nov 10, 2018 6:41 pm
- Forum: Lewis Structures
- Topic: Formal charge question
- Replies: 9
- Views: 933
Re: Formal charge question
For all of the Lewis structure questions I've done so far, I have only aimed for 0 formal charges for the most stable structure. If it was a polyatomic/monatomic ion, then I aim for one atom having the indicated charge.
- Sat Nov 10, 2018 6:29 pm
- Forum: Limiting Reactant Calculations
- Topic: Actual Yield
- Replies: 7
- Views: 1223
Re: Actual Yield
Our calculations will only give us the theoretical yields. The actual yield will always be given to us according to experimental results.
- Sat Nov 10, 2018 6:10 pm
- Forum: Electronegativity
- Topic: Electronegativity
- Replies: 8
- Views: 752
Re: Electronegativity
Greater electronegativity is the same as saying greater attraction of other electrons.
- Sat Nov 03, 2018 4:30 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg equation
- Replies: 3
- Views: 849
Re: Rydberg equation
They are both correct. However, professor Lavelle prefers using negative signs to clearly indicate that higher n results in higher energy.
- Sat Nov 03, 2018 4:26 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: En Equation - Why the Negative?
- Replies: 2
- Views: 1007
Re: En Equation - Why the Negative?
We use the negative sign to clearly indicate that energy increases as n increases.
- Sat Nov 03, 2018 4:16 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: 2.51 6th Edition
- Replies: 1
- Views: 210
Re: 2.51 6th Edition
For Bi and Si, you are finding the odd number of electrons in the p orbitals. However, for Ta and Ni, you are finding the odd number of electrons in the d orbitals
- Sat Oct 27, 2018 5:44 pm
- Forum: DeBroglie Equation
- Topic: Kg vs Grams
- Replies: 6
- Views: 687
Re: Kg vs Grams
Within this class, I believe that we will only be using kg when dealing with energy and momentum.
- Sat Oct 27, 2018 5:37 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Degeneracy
- Replies: 7
- Views: 3340
Re: Degeneracy
For hydrogen, all orbitals share the same energy, so the degeneracy of an orbital simply depends on how many exist. For multi-electron atoms, only orbitals that share the same l quantum number have the same energy, so the degeneracy of an orbital would then depend on how many possible orbitals is po...
- Sat Oct 27, 2018 5:14 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenberg- In relation to wavelength
- Replies: 7
- Views: 741
Re: Heisenberg- In relation to wavelength
Because of the inverse relationship between momentum and wavelength shown in the de Broglie equation(λ=h/p), increasing the uncertainty of momentum will decrease the uncertainty of wavelength.
- Sat Oct 27, 2018 5:14 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenberg- In relation to wavelength
- Replies: 7
- Views: 741
Re: Heisenberg- In relation to wavelength
Because of the inverse relationship between momentum and wavelength shown in the de Broglie equation(λ=h/p), increasing the uncertainty of momentum will decrease the uncertainty of wavelength.
- Sat Oct 20, 2018 6:37 pm
- Forum: Properties of Light
- Topic: Do I have to memorize the spectrum?
- Replies: 20
- Views: 1731
Re: Do I have to memorize the spectrum?
I believe that it will be important to know the order of the regions of the electromagnetic spectrum, as I feel that questions on ordering waves based on frequency, wavelength, or energy will pop up on the test
- Sat Oct 20, 2018 6:26 pm
- Forum: Properties of Light
- Topic: Grades
- Replies: 7
- Views: 678
Re: Grades
I believe that we will not see our grades until the end of the quarter, at least that is what is suggested by our syllabus. We can only keep track of our scores ourselves with the tests and homework being passed back.
- Sat Oct 20, 2018 6:13 pm
- Forum: Properties of Light
- Topic: color of light
- Replies: 11
- Views: 1097
Re: color of light
Both wavelength and frequency play a part in determining the color of light. It's just that visible spectrum diagrams always use wavelength to indicate the color.
- Sun Oct 14, 2018 5:55 pm
- Forum: Properties of Light
- Topic: Speed of Light
- Replies: 41
- Views: 2865
Re: Speed of Light
Anjali 4A wrote:Will we be provided all of these constants/equations during the tests, midterms and final?
I am sure that we will get a cover sheet with all of the constants/equations as we did on the first test on all future tests as well.
- Sun Oct 14, 2018 5:49 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test #2
- Replies: 3
- Views: 369
Re: Test #2
By next week, are you referring to 10/15 through 10/19 or 10/22 through 10/26?
- Sun Oct 14, 2018 2:05 pm
- Forum: Properties of Light
- Topic: E=hv
- Replies: 13
- Views: 1110
Re: E=hv
Tamera Scott 3L wrote:I've also seen E=hf once, does anyone know if that is the same as E=hv?
I believe that f and v both symbolize frequency. I think that v is just more commonly used in chemistry while f is more preferred in physics.
- Tue Oct 02, 2018 10:02 pm
- Forum: Empirical & Molecular Formulas
- Topic: Question F3(6th Edition)
- Replies: 3
- Views: 238
Question F3(6th Edition)
Question: (a) Write the formula for nitric acid. (b) Without doing a calculation, estimate which element in nitric acid occurs with the greatest mass percentage. I am only using this problem as an example. When the question asks for the formula of a certain compound, are we supposed to figure it out...
- Tue Oct 02, 2018 9:49 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Question E1(6th Edition)
- Replies: 7
- Views: 714
Re: Question E1(6th Edition)
Considering what Dr.Lavelle said in class on Monday, I believe that it is fine for the answers' units to be in any form for problems in homework and tests when it is not specified. He mentioned that we may want our units to be simplified a certain way only if we are in a lab setting.
- Sat Sep 29, 2018 9:24 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Question E1(6th Edition)
- Replies: 7
- Views: 714
Question E1(6th Edition)
Question: The field of nanotechnology offers some intriguing possibilities, such as the creation of fibers one atom wide. Suppose you were able to string together 1.00 mol Ag atoms, each of radius 144 pm, into one of these fibers by encapsulating them in carbon nanotubes (see Chapter 6). How long wo...