Search found 31 matches
- Mon Mar 12, 2018 10:46 pm
- Forum: *Nucleophiles
- Topic: What are nucleophiles?
- Replies: 3
- Views: 1726
What are nucleophiles?
I'm confused on what nucleophiles are. Also what type of problems will they show up in? Thanks
- Mon Mar 12, 2018 10:33 pm
- Forum: Phase Changes & Related Calculations
- Topic: Test #1
- Replies: 4
- Views: 644
Re: Test #1
Yes, that is what I put as my explanation. I also said that it was an endothermic process.
- Mon Mar 12, 2018 10:14 pm
- Forum: Calculating Work of Expansion
- Topic: Different work problems?
- Replies: 2
- Views: 460
Re: Different work problems?
You would use w=-PΔV for an irreversible pathway and -nRTlnV2/V1 for a reversible pathway. You solve for ΔU normally using ΔU = w +q
- Wed Mar 07, 2018 11:28 pm
- Forum: First Order Reactions
- Topic: UA worksheet [ENDORSED]
- Replies: 2
- Views: 393
Re: UA worksheet [ENDORSED]
-You can solve for k using the first order half life equation.
-Turn 30 days in seconds
-Use ln[A]=-kt+ln[A]initial and rearrange so that you are solving for [A]/[A]initial
-Plug in the k value and time
-Multiply what you get for [A]/[A]initial by 100 to get the percentage
-Turn 30 days in seconds
-Use ln[A]=-kt+ln[A]initial and rearrange so that you are solving for [A]/[A]initial
-Plug in the k value and time
-Multiply what you get for [A]/[A]initial by 100 to get the percentage
- Wed Mar 07, 2018 11:21 pm
- Forum: Second Order Reactions
- Topic: Second Order
- Replies: 3
- Views: 594
Re: Second Order
Since 0.25 is half of 0.50, you can use the second order half life equation to help you with this problem. For half life, it only depends on your initial concentration, k, and t. You can see how there are different initial concentrations and because they are different you know that they will have di...
- Wed Mar 07, 2018 11:15 pm
- Forum: Second Order Reactions
- Topic: 15.35
- Replies: 6
- Views: 1085
Re: 15.35
You would use the second order half life equation, which is t1/2= 1/k[A]initial to solve for k. Then plug your values into 1/[A] = kt + 1/[A]initial to find the time.
- Tue Feb 27, 2018 11:47 pm
- Forum: General Rate Laws
- Topic: Negative 1/a
- Replies: 8
- Views: 1115
Re: Negative 1/a
In addition, the rate needs to be positive in the end.
- Tue Feb 27, 2018 11:35 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: What is the order of the reaction? [ENDORSED]
- Replies: 4
- Views: 543
Re: What is the order of the reaction? [ENDORSED]
The order of your reaction is the n value. It shows up in the differential rate law where
Rate=k[R]^n (so n=0 in a zero order reaction, n=1 in a 1st order reaction, etc)
Rate=k[R]^n (so n=0 in a zero order reaction, n=1 in a 1st order reaction, etc)
- Tue Feb 27, 2018 12:52 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Midterm 6A (Multiple Choice)
- Replies: 4
- Views: 1048
Midterm 6A (Multiple Choice)
Question 6A Answer: C8H18(l) (at 298 K) has higher molar entropy than CH4(g), because C8H18 is a larger molecule than CH4, and larger molecules have more chemical bonds and can store energy in more ways than smaller molecules. How do you know that C8H18 has a higher molar entropy when it is a liquid...
- Tue Feb 20, 2018 7:49 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anode/Cathode
- Replies: 2
- Views: 324
Re: Anode/Cathode
The anode relates to the oxidation reaction and the cathode with the reduction reaction. My TA said a way to remember this is anode and oxidation both start with vowels and cathode and reduction both start with consonants.
- Mon Feb 19, 2018 1:00 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Acidic vs. Basic
- Replies: 2
- Views: 329
Acidic vs. Basic
Will all the questions on the test be under acidic conditions? If not, how do you know the number of H2O and H+ molecules you add under acidic conditions and how many H2O and OH- molecules you add when the reaction is under basic conditions?
- Mon Feb 19, 2018 12:53 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: E vs E naught
- Replies: 3
- Views: 4273
Re: E vs E naught
Yes, E°is under standard conditions (at 1 atm and 25°C) just like G°.
- Mon Feb 19, 2018 12:47 am
- Forum: Balancing Redox Reactions
- Topic: Standard Reduction Potential
- Replies: 3
- Views: 478
Re: Standard Reduction Potential
I think because standard reduction potential is an intensive property so the amount that the reaction occurs doesn't matter.
- Tue Feb 13, 2018 9:35 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Qrev
- Replies: 2
- Views: 1068
Re: Qrev
The "rev" part means that the reaction is reversible. Reversible reactions are ideal and happen at equilibrium.
- Tue Feb 13, 2018 11:31 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: practice midterms
- Replies: 2
- Views: 391
Re: practice midterms
Here's the link: viewtopic.php?f=160&t=27112
- Tue Feb 13, 2018 1:30 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: delta u [ENDORSED]
- Replies: 3
- Views: 693
Re: delta u [ENDORSED]
^Yes, everything you said is correct. ΔU=0 for an isothermal process.
- Fri Feb 09, 2018 11:34 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: disorder & entropy
- Replies: 2
- Views: 310
Re: disorder & entropy
Adding on, the equation S=KblnW shows that with more microstates (W=number of microstates^# of particles in the system), there is an increase in entropy.
- Fri Feb 09, 2018 11:28 pm
- 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: Today's Review Session #9.35
- Replies: 1
- Views: 342
Today's Review Session #9.35
Today in the midterm review session we talked about Problem 9.35 and how Container A and Container C actually have the same entropy. I'm unclear on how for Container C, C= 3/2 R. I understand that you add something onto 5/2R but after that I'm confused. Thanks for the help
- Fri Feb 09, 2018 11:15 pm
- 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: Box 9.6
- Replies: 1
- Views: 407
Re: Box 9.6
I think the C values are different because now you are in a different phase and there are specific C values for each phase. For example with water: The molar heat capacity of liquid water = 75.29 J·K-1·mol-1, the molar heat capacity of ice is 37.1 J·K-1·mol-1, and the molar heat capacity of water va...
- Fri Feb 02, 2018 3:56 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff Eq.
- Replies: 5
- Views: 1045
Re: Van't Hoff Eq.
Can someone please explain what it means for ∆S°to be constant? I think Dr. Lavelle was explaining this at the end of lecture (something to do with the difference not changing between the two ∆S° values), but I didn't quite catch it all. Thanks!
- Fri Feb 02, 2018 3:47 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: When to use Q versus K [ENDORSED]
- Replies: 6
- Views: 2643
When to use Q versus K [ENDORSED]
When do you use the equation ΔG= ∆G°+ RTlnQ versus ΔG= ∆G°+ RTlnK?
- Thu Feb 01, 2018 12:56 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Adiabatic [ENDORSED]
- Replies: 4
- Views: 507
Re: Adiabatic [ENDORSED]
I'm not completely sure but I believe that your reasoning is correct. Adiabatic means that no heat is gained or lost by the system, so q does equal zero and energy is only transferred as work.
- Sat Jan 27, 2018 2:24 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible vs Irreversible
- Replies: 2
- Views: 315
Re: Reversible vs Irreversible
Would someone be able to provide an example for when reversible reactions are isothermal and an example of when they are not? I'm a little confused...Thanks!
- Wed Jan 24, 2018 7:12 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Homework Problem 8.67
- Replies: 3
- Views: 542
Re: Homework Problem 8.67
For Part b of this problem, what does "atomize" mean/refer to in the solutions manual? Thanks!
- Wed Jan 24, 2018 6:59 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Calorimetry
- Replies: 4
- Views: 524
Re: Calorimetry
You can leave the temperature in degrees Celsius.
- Fri Jan 19, 2018 4:09 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated system
- Replies: 3
- Views: 451
Re: Isolated system
ΔU=0 in an isolated system. Energy cannot be transferred between the system and surroundings.
- Fri Jan 19, 2018 3:58 pm
- Forum: Calculating Work of Expansion
- Topic: Integral from Today's Lecture
- Replies: 3
- Views: 413
Integral from Today's Lecture
From today's lecture, we learned about an integral you can use to "sum an infinite number of steps" regarding expansion. (Integral: W=- V1∫ V2 P dv). I'm confused what this means and what it is used for. Would someone be able to explain? Thanks!
- Fri Jan 19, 2018 3:45 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Difference between Closed and Isolated
- Replies: 10
- Views: 13375
Re: Difference between Closed and Isolated
A closed system can share heat, whereas an isolated system cannot. Both cannot share particles with their surroundings.
- Sun Jan 14, 2018 7:53 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Recording Lectures
- Replies: 2
- Views: 408
Recording Lectures
For anyone that was in Dr. Lavelle's 14A class, has he given permission to record his lectures (to use if we don't catch something from the PowerPoint or for studying for tests/midterm...never to post anywhere/distribute)? Thanks!
- Sun Jan 14, 2018 5:44 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Reaction Enthalpy Definition
- Replies: 7
- Views: 608
Re: Standard Reaction Enthalpy Definition
I don't think that it has to always be at that temperature. A majority of the times, it is at 25 degrees Celsius/298 Kelvin. However, the temperature can vary if the reaction is stated at a specified temperature of interest.
- Sun Jan 14, 2018 5:35 pm
- Forum: Phase Changes & Related Calculations
- Topic: Isolated vs Closed Systems
- Replies: 2
- Views: 209
Re: Isolated vs Closed Systems
A closed system can exchange energy with its surroundings whereas an isolated system cannot. An example of a closed system is an ice pack (heat is transferred) and an example of an isolated system is a thermos with hot soup in it (heat cannot flow out of the system).