Search found 53 matches
- Sat Mar 17, 2018 2:31 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.27
- Replies: 1
- Views: 142
Re: 14.27
you can cancel the F
- Sat Mar 17, 2018 12:03 pm
- Forum: Phase Changes & Related Calculations
- Topic: Reversible Expansions
- Replies: 3
- Views: 368
Re: Reversible Expansions
In a TA review session he explained that when you have a rev process you are extracting the max work bc you are making such small changes that you can appoximate P-internal = P-external at every instant. PV=nRT. P=nRT/v. substitute w=-nRT/V and integrate w respect to V. this is where you get w = -nR...
- Sat Mar 17, 2018 11:58 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: 14.93
- Replies: 1
- Views: 288
- Sat Mar 17, 2018 11:58 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Concentration cells
- Replies: 2
- Views: 278
- Sat Mar 17, 2018 11:55 am
- Forum: *Nucleophiles
- Topic: nucleophile?
- Replies: 4
- Views: 723
Re: nucleophile?
nucleophiles also usually have a partial - charge like the example from the lecture.
- Sat Mar 17, 2018 11:53 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: State functions?
- Replies: 9
- Views: 666
Re: State functions?
Why are heat and work not state functions? G H and S are all quantities of energy (in the form of heat or disorder) contained within a compound. Work and heat are CHANGES in energy. How you change energy depends on the PATH. your altitude on a mountain = state function = G H S how you got to the to...
- Sat Mar 17, 2018 11:48 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Question 14.41
- Replies: 6
- Views: 524
Re: Question 14.41
You want e- to flow anode to cathode. At the anode Cu(s) > Cu2+ + 2e-. At the cathode Cu2+ + 2e- > Cu(s). So the anode [] is a product and cathode [] is a reactant. Since you want postive E and Q=P/R, so, using the eq, you can see that anode should always have lower [].
- Sat Mar 17, 2018 11:42 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagram: Porous Disk and Salt Bridge
- Replies: 5
- Views: 383
- Sat Mar 17, 2018 11:39 am
- Forum: *Nucleophilic Substitution
- Topic: Transition States
- Replies: 3
- Views: 1126
Re: Transition States
I use this:
A---B--C is the transition state since it has a lot of energy, and shows the collision of the particles.
A---B--C is the transition state since it has a lot of energy, and shows the collision of the particles.
- Sat Mar 17, 2018 11:28 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activation Energy
- Replies: 5
- Views: 446
Re: Activation Energy
In the question below, each peak is an activation energy of a step in the reaction. The top of each peak represents an activated complex / transition state.
- Sat Mar 17, 2018 11:23 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy of Surroundings vs. System
- Replies: 2
- Views: 304
Re: Entropy of Surroundings vs. System
When you ADD heat, ∆H is +. Ex - adding heat to boil water has +∆H, so ∆S = +∆H/T.
- Sat Mar 17, 2018 11:19 am
- Forum: Phase Changes & Related Calculations
- Topic: Sign for compression vs expansion
- Replies: 4
- Views: 406
Re: Sign for compression vs expansion
W=-P∆V. ∆V = V_f - V_i.
- Sat Mar 17, 2018 11:17 am
- Forum: Balancing Redox Reactions
- Topic: Ranking elements
- Replies: 8
- Views: 625
Re: Ranking elements
I like to keep this chart in mind.
- Sat Mar 17, 2018 11:14 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Homework 14.17
- Replies: 2
- Views: 209
Re: Homework 14.17
I attached my work:
I wrote down the potentials for all the possible 1/2 reactions, and found the pair that summed to the most +, since this is a galvanic cell (E>0). Then you just balance and add them. :)
I wrote down the potentials for all the possible 1/2 reactions, and found the pair that summed to the most +, since this is a galvanic cell (E>0). Then you just balance and add them. :)
- Sat Mar 17, 2018 10:50 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Total entropy change determining spontaneity
- Replies: 3
- Views: 344
Re: Total entropy change determining spontaneity
Since total entropy of an isolated system must always increase (2nd law) - then ∆S_tot must always be positive. Order cannot come from disorder without an input on energy. For example, think about freezing ice. Liquid > solid is a decrease of energy, but you must put in MORE energy (electrical from ...
- Sat Mar 17, 2018 10:44 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: total entropy of the system
- Replies: 3
- Views: 317
- Sat Mar 17, 2018 10:43 am
- Forum: Biological Examples (*DNA Structural Transitions, etc.)
- Topic: 9.69
- Replies: 1
- Views: 663
Re: 9.69
You get a -dG from the two reactions, and this energy is used to drive the ATP production. It's a transfer of energy between two separate entities, so the heat given off by the two reactions is used to make ATP. Like hot water mixing with cold water, the hot water gives off energy and the cold water...
- Thu Mar 15, 2018 8:20 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Gibbs and Activation Energy
- Replies: 4
- Views: 428
Gibbs and Activation Energy
Hi! Is there a relationship between Gibbs energy and activation energy? Thanks! :)
- Wed Mar 14, 2018 12:43 pm
- Forum: *Free Energy of Activation vs Activation Energy
- Topic: 4.29 Green book
- Replies: 3
- Views: 1451
Re: 4.29 Green book
this can be seen in the arrhenius equation:
https://www.chemguide.co.uk/physical/basicrates/arrhenius.html
https://www.chemguide.co.uk/physical/basicrates/arrhenius.html
- Wed Mar 14, 2018 12:39 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.53
- Replies: 3
- Views: 375
Re: 8.53
Christy Zhao 1H wrote:How do you know to use the equation?
Since its in a bomb calorimeter, the volume is held constant, so c=3/2R for an ideal gas.
- Wed Mar 14, 2018 12:37 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Is enthalpy a state function?
- Replies: 12
- Views: 1186
Re: Is enthalpy a state function?
You can think of the enthalpy of formation as the heat stored in the bonds of the molecule, formed from its components.
- Mon Mar 05, 2018 12:42 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: rate order vs contribution to overall rate
- Replies: 3
- Views: 268
Re: rate order vs contribution to overall rate
How does the overall rate indicate these relationships?
- Mon Mar 05, 2018 12:41 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 0 order
- Replies: 6
- Views: 2211
Re: 0 order
How does this graphic representation correlate to the presence of a catalyst?
- Mon Mar 05, 2018 12:39 pm
- Forum: *Free Energy of Activation vs Activation Energy
- Topic: Endergonic and exergonic free energy reaction profiles?
- Replies: 2
- Views: 1263
Re: Endergonic and exergonic free energy reaction profiles?
I believe these terms are used to refer to the same reactions as exothermic and endothermic.
- Wed Feb 28, 2018 12:37 pm
- Forum: First Order Reactions
- Topic: 15.15
- Replies: 4
- Views: 292
Re: 15.15
Since the rate increase is linear to reactant concentration increase, it implies it's first order.
- Wed Feb 28, 2018 12:36 pm
- Forum: First Order Reactions
- Topic: Direct Proportions and First Order
- Replies: 5
- Views: 297
Re: Direct Proportions and First Order
First order indicates that doubling the reactant concentration doubles the rate because rate = k [A]^1
- Wed Feb 28, 2018 12:34 pm
- Forum: Zero Order Reactions
- Topic: Half-life of Zero Order [ENDORSED]
- Replies: 4
- Views: 329
Re: Half-life of Zero Order [ENDORSED]
I thought we only needed to know half-lives for first-order reactions?
- Mon Feb 19, 2018 3:05 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: 14.33
- Replies: 1
- Views: 206
Re: 14.33
∆G is a state function, so you can add them. E_cell is NOT a state function, so you can't simply add them. This is why you have to convert to ∆G and back to E.
viewtopic.php?t=3754
viewtopic.php?t=3754
- Mon Feb 19, 2018 3:02 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: 14.51
- Replies: 1
- Views: 172
Re: 14.51
I interpreted it as there is a flow of electrons, which, if put into a circuit, would allow for electric work to be used, despite electrons are flowing cathode to the anode.
- Mon Feb 19, 2018 2:59 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Problem 14.23 (b)
- Replies: 1
- Views: 208
Re: Problem 14.23 (b)
Br is the anode since its losing electrons, going from Br- to Br2(l). Br2(l) has an oxidation number of 0, while Br- has an oxidation number of -1. The reverse logic can be used on Hg.
- Mon Feb 19, 2018 2:57 pm
- Forum: Balancing Redox Reactions
- Topic: 14.15c
- Replies: 2
- Views: 217
Re: 14.15c
Vincent Chiang 1L wrote:The KOH is there as a salt bridge to allow for the flow of ions.
Thank you! How are we supposed to know its KOH? Is this a common convention, like Pt(s)? Thanks!
- Sun Feb 18, 2018 1:02 pm
- Forum: Balancing Redox Reactions
- Topic: 14.15c
- Replies: 2
- Views: 217
14.15c
Hi! I was wondering why in the solutions manual potassium is included in the final cell diagram? Thanks!
- Thu Feb 15, 2018 9:12 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Delta G= Wmax
- Replies: 8
- Views: 996
Re: Delta G= Wmax
Whats the relationship between free energy and max work - are they equal?
- Thu Feb 15, 2018 9:11 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Units for Gibbs Free Energy
- Replies: 4
- Views: 487
Re: Units for Gibbs Free Energy
When a problem asks for Gibbs Free energy in "kJ" does this mean kJ/mol or just kJ?
- Thu Feb 15, 2018 9:10 am
- Forum: Balancing Redox Reactions
- Topic: Salt Bridges
- Replies: 14
- Views: 616
Re: Salt Bridges
In a battery, like a AAA battery, what serves as a salt bridge?
- Wed Feb 07, 2018 7:03 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 11.83
- Replies: 3
- Views: 515
Re: 11.83
This isn't what the solution manual says? Can someone explain how to approach this problem?
- Mon Feb 05, 2018 2:23 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge [ENDORSED]
- Replies: 4
- Views: 801
Re: Salt Bridge [ENDORSED]
What is the porous disk composed of? Does it act differently than the salt bridge in any way?
- Mon Feb 05, 2018 2:22 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anode and Cathode [ENDORSED]
- Replies: 4
- Views: 402
Re: Anode and Cathode [ENDORSED]
I may be remembering incorrectly, but in high school, I remember one side being negative and the other positive, is this convention used? If so which side correlates to which sign? Thanks!!
- Mon Feb 05, 2018 2:21 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Determining reduction or oxidation
- Replies: 4
- Views: 761
Re: Determining reduction or oxidation
The ion which is reduced will gain electrons, and its oxidation number will decrease. On the other hand, the ion which is oxidized will lose electrons and its oxidation number will increase.
- Thu Feb 01, 2018 2:08 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Regarding the equation deltaS=nCln(Tf/Ti)
- Replies: 3
- Views: 533
Re: Regarding the equation deltaS=nCln(Tf/Ti)
Also, when do we need to include n, the number of moles, as I see it omitted in some forms of the equations? Thanks!
- Thu Feb 01, 2018 2:07 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 9.11 [ENDORSED]
- Replies: 3
- Views: 271
Re: 9.11 [ENDORSED]
We also use P1/P2 as opposed to V2/V1 since pressure and volume are inversely related. P1V1=P2V2.
- Thu Feb 01, 2018 2:06 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: sign of entropy
- Replies: 11
- Views: 762
Re: sign of entropy
Additionally, during a process of expansion entropy increases as there are more possible states.
- Tue Jan 23, 2018 4:38 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: When to use Cv or Cp? to calculate change in Entropy
- Replies: 3
- Views: 1271
Re: When to use Cv or Cp? to calculate change in Entropy
It depends on the type of system the reaction is being carried out in. If the problem specifies that it is isothermal, use Cp. It it is being carried out in isochoric, use Cv. If it is isobaric, use Cp to calculate q because pressure is not changing and change in volume will be accounted for in cal...
- Tue Jan 23, 2018 4:36 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Irreversible vs. Reversible [ENDORSED]
- Replies: 10
- Views: 826
Re: Irreversible vs. Reversible [ENDORSED]
To clarify: will irreversible expansion be in test #1? I thought Dr. Lavelle said that it would not be tested, but it appears in the assigned homework problems? Thanks!
- Tue Jan 23, 2018 4:36 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Irreversible vs. Reversible [ENDORSED]
- Replies: 10
- Views: 826
Re: Irreversible vs. Reversible [ENDORSED]
To clarify: will irreversible expansion be in test #1? I thought Dr. Lavelle said that it would not be tested, but it appears in the assigned homework problems? Thanks!
- Tue Jan 23, 2018 4:32 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Week 3 Test Topic is endorsed
- Replies: 37
- Views: 3064
Re: Week 3 Test Topic is endorsed
Will we be tested on memorizing the formulas in section 8.10: A Molecular Interlude: The Origin of the Heat Capacities of Gases? Thanks!
- Sun Jan 21, 2018 1:04 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Equipartition theorem and Degrees of Freedom
- Replies: 1
- Views: 142
Equipartition theorem and Degrees of Freedom
Hi! I was wondering if we need to know the Equipartition theorem and Degrees of Freedom and the formulas for test 1, as I don't remember going over it in class? Thanks!
- Tue Jan 16, 2018 7:54 pm
- Forum: Phase Changes & Related Calculations
- Topic: Steam burning more than water question
- Replies: 4
- Views: 218
Re: Steam burning more than water question
This can be seen in the phase change diagram, as the long section during which heat is added to change liquid to gas represents a significant amount of energy. This energy, when transferred to a hand, causes a more severe burn.
- Tue Jan 16, 2018 7:52 pm
- Forum: Phase Changes & Related Calculations
- Topic: Types of Systems
- Replies: 10
- Views: 869
Re: Types of Systems
Is there a type of system which somehow exchanges particles but not heat? Or is this impossible?
- Tue Jan 16, 2018 7:50 pm
- Forum: Phase Changes & Related Calculations
- Topic: Gas Law
- Replies: 2
- Views: 242
Re: Gas Law
Additionally, it seems, that in the textbook we can usually assume the gas is behaving ideally, unless stated otherwise? Someone correct me if I'm wrong.
- Thu Jan 11, 2018 10:15 am
- Forum: Phase Changes & Related Calculations
- Topic: Exothermic Rxn
- Replies: 6
- Views: 500
Re: Exothermic Rxn
Is there another way to determine if a reaction can occur spontaneously?
- Thu Jan 11, 2018 10:05 am
- Forum: Administrative Questions and Class Announcements
- Topic: Constants & Equations Sheet
- Replies: 3
- Views: 227
Re: Constants & Equations Sheet
Is this sheet posted anywhere so we can start working with it? Thanks!
- Thu Jan 11, 2018 10:01 am
- Forum: Administrative Questions and Class Announcements
- Topic: Lecture Outline
- Replies: 2
- Views: 236
Lecture Outline
Does anyone know if there is a schedule posted anywhere which outlines which sections of the book correspond to each lecture? Thanks :)