Search found 51 matches
- Sat Mar 14, 2020 5:42 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: What was your favorite chem topic?
- Replies: 137
- Views: 13112
Re: What was your favorite chem topic?
acids/bases!
- Sat Mar 14, 2020 5:40 pm
- Forum: Ideal Gases
- Topic: Weak vs Strong Acids and Bases
- Replies: 3
- Views: 382
Re: Weak vs Strong Acids and Bases
strong acids/bases dissociate completely; in contrast, weak acids/bases only partially dissociate, so you'd have to use the ka/kb value to figure out pH, concentration, etc.
- Sat Mar 14, 2020 5:39 pm
- Forum: Student Social/Study Group
- Topic: Coronavirus Joke
- Replies: 14
- Views: 1853
Re: Coronavirus Joke
only good thing to come out of the coronavirus are memes like this
- Sat Mar 14, 2020 5:37 pm
- Forum: Ideal Gases
- Topic: Kc
- Replies: 7
- Views: 635
Re: Kc
for gases and aqueous substances you use concentrations
- Sat Mar 14, 2020 5:34 pm
- Forum: Administrative Questions and Class Announcements
- Topic: final exam - question
- Replies: 6
- Views: 713
final exam - question
sorry to ask this because I know Professor Lavelle's been working on the easiest/simplest way for us to take the final, but I was wondering whether we just submit the answers on the final exam? or do we have to write out the work on CCLE? If not, are we still able to get partial credit or is it all ...
- Fri Mar 13, 2020 9:03 pm
- Forum: Administrative Questions and Class Announcements
- Topic: take home FINAL DEADLINE
- Replies: 15
- Views: 1148
Re: take home FINAL DEADLINE
I'm pretty sure it's going to be the same timeframe as the normal final.
- Fri Mar 13, 2020 7:22 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Identification
- Replies: 8
- Views: 558
Re: Identification
In addition to what everyone else said, it also includes certain elements that exist in their normal state in multiples (like P5)
- Fri Mar 13, 2020 6:31 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius Equation
- Replies: 8
- Views: 599
Re: Arrhenius Equation
Sidharth D 1E wrote:To expand on that, reactions that give a straight line when lnkr is plotted against 1/T are said to show Arrhenius behavior
What is arrhenius behavior?
- Wed Mar 11, 2020 10:01 pm
- Forum: Administrative Questions and Class Announcements
- Topic: ENDGAME Review Session
- Replies: 71
- Views: 5811
Re: ENDGAME Review Session
Thanks so much Lyndon! Your review sessions and worksheets were incredibly helpful!
- Wed Mar 11, 2020 9:59 pm
- Forum: Administrative Questions and Class Announcements
- Topic: "Open Book" Final?
- Replies: 30
- Views: 2160
Re: "Open Book" Final?
Do you know if chemistry community will be locked while we take the final?
- Wed Mar 11, 2020 9:58 pm
- Forum: Student Social/Study Group
- Topic: Final Exam
- Replies: 22
- Views: 1624
Re: Final Exam
Diana Chavez-Carrillo 2L wrote:Does anyone know when we will be given our take-home final? Is it still going to be on Sunday?
I think it's still going to be sunday, as there's nothing to indicate otherwise
- Wed Mar 11, 2020 9:56 pm
- Forum: Student Social/Study Group
- Topic: Final Exam
- Replies: 22
- Views: 1624
Re: Final Exam
Philip wrote:How are you guys going to be studying for the final
I'm planning to look over the study guide Dr. Lavelle sent out, do the endgame worksheet Lyndon posted, and review my notes/ do practice hw problems.
- Wed Mar 11, 2020 9:54 pm
- Forum: Student Social/Study Group
- Topic: Final Exam
- Replies: 22
- Views: 1624
Re: Final Exam
Clara Cho 2K wrote:Do you think we will still meet for discussion?
I don't think so, I'm pretty sure we just email our hw in
- Wed Mar 11, 2020 9:53 pm
- Forum: *Free Energy of Activation vs Activation Energy
- Topic: Activation Energy
- Replies: 9
- Views: 1516
Re: Activation Energy
Catalysts create an alternate pathway - they speed up reactions by lowering Ea.
- Wed Mar 11, 2020 9:51 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: K vs k1/k'1
- Replies: 6
- Views: 1497
Re: K vs k1/k'1
I'm pretty sure either work
- Wed Mar 11, 2020 9:47 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: What is 'A'?
- Replies: 5
- Views: 434
Re: What is 'A'?
In my notes, 'A' is defined as the frequency factor or pre-exponential factor (including # of collisions with correct orientation). What does this mean? Is this what we're trying to calculate with the Arrhenius equation? I'm pretty sure it's given. From what I remember in class, Dr. Lavelle said it...
- Wed Mar 11, 2020 9:34 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts and Reaction Pathways
- Replies: 6
- Views: 456
Re: Catalysts and Reaction Pathways
Besides adding a catalyst, can increasing the temperature, increasing pressure, or decreasing volume speed up a reaction with the large activation energy? I'd assume that it would change the reaction forwards/backwards in terms of Le Chatelier's Principle? but I'm honestly not too sure how it inter...
- Wed Mar 11, 2020 9:32 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Pre-Equilibrium Approach
- Replies: 2
- Views: 272
Re: Pre-Equilibrium Approach
The pre-equilibrium approach says that the intermediate is formed and sustained in a rapid formation reaction and its reverse, and you assume it reaches a sort of equilibrium. Instead, the steady state approach assumes that concentrations of the intermediates are low and don't change. As you don't w...
- Wed Mar 11, 2020 9:22 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Temperature and Reaction Rate
- Replies: 6
- Views: 483
Re: Temperature and Reaction Rate
K and temperature are proportional, so increasing temperature also increases k (increasing your rxn rate)
- Wed Mar 11, 2020 9:21 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 490
- Views: 622252
Re: Saying Thank You to Dr. Lavelle
Dear Dr. Lavelle,
Thank you so much for all the work you put into teaching us this quarter! I really appreciate all the effort you put into lectures and organizing our review sessions, and I learned so much.
Thank you so much for all the work you put into teaching us this quarter! I really appreciate all the effort you put into lectures and organizing our review sessions, and I learned so much.
- Wed Mar 11, 2020 4:08 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: intermediate
- Replies: 26
- Views: 2104
Re: intermediate
The intermediate is formed and used up, and it doesn't appear in the overall chemical equation
- Wed Mar 11, 2020 4:05 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Units for Thermo Calculations
- Replies: 3
- Views: 417
Re: Units for Thermo Calculations
I'm not completely sure, but I think Gibb's free energy is usually given in kJ/mol and delta H is given in J/mol. To be honest, though, I think either would work as long as it's the right one for the problem/right one with the information given
- Wed Mar 11, 2020 4:02 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Bottle Neck Effect
- Replies: 4
- Views: 381
Re: Bottle Neck Effect
005162520 wrote:Is the second step our first step and the second step or fast step?
I'm pretty sure it's when the second step is slow, so it limits how fast the first step can go
- Tue Mar 10, 2020 4:32 pm
- Forum: Administrative Questions and Class Announcements
- Topic: final
- Replies: 6
- Views: 609
Re: final
Rida Ismail 2E wrote:My guess is there will probably be an online alternative. I'm sure that Dr. Lavelle will send out an email in the next few hours about what he is going to do about finals.
Gotchu, thanks!!
- Tue Mar 10, 2020 4:15 pm
- Forum: Administrative Questions and Class Announcements
- Topic: final
- Replies: 6
- Views: 609
final
I know the news just broke, but does anyone know how the final is going to work?
- Tue Mar 10, 2020 3:04 pm
- Forum: Second Order Reactions
- Topic: determining order
- Replies: 9
- Views: 646
Re: determining order
You determine the order from experimental data - the method usually depends on the information given in the problem.
- Tue Mar 10, 2020 2:56 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Advice from a Medical Student - Part II [ENDORSED]
- Replies: 298
- Views: 305172
Re: Advice from a Medical Student - Part II [ENDORSED]
Does anyone know when the best time to start preparing for the MCAT is? This is something that depends on each individual. Some people try to study while still taking classes. I took a gap year where I studied for the MCAT and did more clinical work. It's completely up to you. What's important to k...
- Tue Mar 10, 2020 2:55 pm
- Forum: Administrative Questions and Class Announcements
- Topic: ENDGAME Review Session
- Replies: 71
- Views: 5811
Re: ENDGAME Review Session
Thank you so much for creating this!!
- Mon Mar 09, 2020 2:09 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Study Advice
- Replies: 73
- Views: 7328
Re: Study Advice
KatrinaPho_2I wrote:If you look up the worksheets that the TA Joyce posts on chem community, they are really helpful. Lyndon's review sessions are also very helpful.
how do you look up the worksheets?
- Mon Mar 09, 2020 1:22 pm
- Forum: General Science Questions
- Topic: Who makes the Final
- Replies: 23
- Views: 1532
Re: Who makes the Final
I'm pretty sure Professor Lavelle makes it.
- Thu Feb 27, 2020 12:15 pm
- Forum: Balancing Redox Reactions
- Topic: Oxygen's oxidation #
- Replies: 6
- Views: 472
Re: Oxygen's oxidation #
in addition to what everyone else said, elements in their standard state have an oxidation number of 0 (so like O2 would have an oxidation number of 0 or H2 would have an oxidation number of 0)
- Tue Feb 11, 2020 6:28 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: delta h and constant temp and pressure
- Replies: 4
- Views: 337
delta h and constant temp and pressure
How is delta H impacted when the system's at constant temperature and pressure?
- Sat Feb 08, 2020 11:07 am
- Forum: Ideal Gases
- Topic: Compressing a gas
- Replies: 5
- Views: 398
Compressing a gas
If a reaction is compressed, I know that it goes to the side with less molecules of gas, but I don't remember the explanation he used in class. Could someone explain that?
- Sat Feb 08, 2020 11:00 am
- Forum: Administrative Questions and Class Announcements
- Topic: Advice from a Medical Student - Part II [ENDORSED]
- Replies: 298
- Views: 305172
Re: Advice from a Medical Student - Part II [ENDORSED]
Does anyone know when the best time to start preparing for the MCAT is?
- Sat Feb 08, 2020 10:49 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Addition of a solid product/reactant
- Replies: 3
- Views: 250
Addition of a solid product/reactant
If you add a solid product/reactant, does the reaction shift? (b/c it isn't in the K expression)
- Fri Feb 07, 2020 10:24 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy
- Replies: 5
- Views: 225
Re: Gibbs Free Energy
- if delta H is negative and delta S is positive, Gibbs Free energy is negative (spontaneous) - if delta H is positive and delta S is positive, T(delta S) has to be greater than delta H for Gibbs Free energy to be negative - if delta H is negative and delta S is negative, delta H has to be larger th...
- Fri Feb 07, 2020 9:56 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: state occupation of phases
- Replies: 7
- Views: 298
Re: state occupation of phases
Gases have their molecules a lot more spread out, liquids are only slightly spread out, and solids have their molecules tightly packed.
- Wed Jan 29, 2020 11:35 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Cpm and Cvm
- Replies: 2
- Views: 195
Cpm and Cvm
Why is Cpm (5/2)R and why is Cvm (3/2)R?
- Wed Jan 29, 2020 11:34 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 4C.3
- Replies: 3
- Views: 144
Re: 4C.3
Ruby Tang 2J wrote:In the relevant section of the textbook, it is explained that for a monatomic ideal gas, Cp = 5/2R, while Cv = 3/2R, where R = 8.3145 J*K-1*mol-1.
Do you know if we'd need to know this on our test, or if they'd give us these values?
- Wed Jan 29, 2020 11:32 am
- Forum: Ideal Gases
- Topic: Inert Gas
- Replies: 12
- Views: 714
Re: Inert Gas
Inert gases don't react with any of the reactants or products.
- Wed Jan 29, 2020 11:31 am
- Forum: Ideal Gases
- Topic: Temperature
- Replies: 17
- Views: 810
Re: Temperature
It depends on the units of the constants in the problem. If it's a problem with molar heat capacity, use kelvin. If specific heat capacity, you would use celsius. Furthermore, usually you'd do delta T, which either would work. The ideal gas law, however, is always in kelvin, and usually if they ask ...
- Wed Jan 29, 2020 11:29 am
- Forum: Ideal Gases
- Topic: non ideal gases
- Replies: 8
- Views: 485
Re: non ideal gases
Increasing the amount of intermolecular forces causes more deviations from ideality, so gases that have a larger molar mass would be less ideal that gases with a lower molar mass. (E.g. CO2 would be less ideal than He)
- Wed Jan 29, 2020 11:26 am
- Forum: Ideal Gases
- Topic: ideal gases
- Replies: 14
- Views: 1007
Re: ideal gases
Adding on to that, most gases are not "perfectly" ideal but they're close enough to the ideal. Gases with large volumes, a high pressure, or a very low temperature can cause deviations from this ideal.
- Sun Jan 26, 2020 6:59 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Aqueos and Gaseous Problems
- Replies: 3
- Views: 514
Re: Aqueos and Gaseous Problems
Use the concentration's (you can still use concentrations for gases).
- Sun Jan 26, 2020 6:52 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Changing K
- Replies: 13
- Views: 541
Re: Changing K
Only temperature can change K. (Pressure, volume, etc. can change the concentrations of reactants/products, but cannot change the equilibrium constant).
- Thu Jan 23, 2020 1:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ka and Kb
- Replies: 10
- Views: 387
Re: Ka and Kb
Ka greater than 10^3 signifies a strong acid. Ka = [CB][H+]/ [HA] The more the acid (HA) dissociates, the more H+ is produced. This increases the Ka because the concentration of the products increases. If the Ka is greater than 10^3, that means it dissociates a lot, making it a strong acid and not a...
- Thu Jan 23, 2020 1:20 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: H20 in the ICE table
- Replies: 26
- Views: 1540
Re: H20 in the ICE table
Alexaaguilera wrote:I think you only include gases when doing an ICE
you include gases as well as aqueous reactants/products
- Thu Jan 23, 2020 12:29 pm
- Forum: Ideal Gases
- Topic: Inert Gases and Equilibrium
- Replies: 6
- Views: 296
Re: Inert Gases and Equilibrium
They don't react with either the reactants or products, so it does not shift equilibrium in either direction.
- Thu Jan 23, 2020 12:25 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6B.3
- Replies: 2
- Views: 120
Re: 6B.3
I don't think there's a part c for 6B.3. Maybe it's a different problem that you're looking at?
- Sat Jan 18, 2020 1:36 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Difference between K and Q?
- Replies: 11
- Views: 578
Re: Difference between K and Q?
The formula's the same and you find it in the same way, but you use current concentrations/pressures for Q and equilibrium concentrations/pressures for K.
- Thu Jan 09, 2020 5:19 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q
- Replies: 2
- Views: 210
Re: Q
It tells you relatively how much of the products or reactants are made. If Q is smaller than K, you don't have as many products made, so the reaction progresses forward to make more products to make Q larger and reach the value of K. If Q is larger than K, it will proceed in the direction of the rev...