Search found 53 matches

by melissa carey 1f
Sat Mar 17, 2018 2:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.27
Replies: 1
Views: 64

Re: 14.27

you can cancel the F
by melissa carey 1f
Sat Mar 17, 2018 12:03 pm
Forum: Phase Changes & Related Calculations
Topic: Reversible Expansions
Replies: 3
Views: 276

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...
by melissa carey 1f
Sat Mar 17, 2018 11:55 am
Forum: *Nucleophiles
Topic: nucleophile?
Replies: 4
Views: 378

Re: nucleophile?

nucleophiles also usually have a partial - charge like the example from the lecture.
by melissa carey 1f
Sat Mar 17, 2018 11:53 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: State functions?
Replies: 9
Views: 383

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...
by melissa carey 1f
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: 281

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 [].
by melissa carey 1f
Sat Mar 17, 2018 11:39 am
Forum: *Nucleophilic Substitution
Topic: Transition States
Replies: 3
Views: 585

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.
by melissa carey 1f
Sat Mar 17, 2018 11:28 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy
Replies: 5
Views: 310

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.
by melissa carey 1f
Sat Mar 17, 2018 11:23 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy of Surroundings vs. System
Replies: 2
Views: 205

Re: Entropy of Surroundings vs. System

When you ADD heat, ∆H is +. Ex - adding heat to boil water has +∆H, so ∆S = +∆H/T.
by melissa carey 1f
Sat Mar 17, 2018 11:19 am
Forum: Phase Changes & Related Calculations
Topic: Sign for compression vs expansion
Replies: 4
Views: 274

Re: Sign for compression vs expansion

W=-P∆V. ∆V = V_f - V_i.
by melissa carey 1f
Sat Mar 17, 2018 11:17 am
Forum: Balancing Redox Reactions
Topic: Ranking elements
Replies: 8
Views: 353

Re: Ranking elements

I like to keep this chart in mind.
by melissa carey 1f
Sat Mar 17, 2018 11:14 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Homework 14.17
Replies: 2
Views: 122

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. :)
by melissa carey 1f
Sat Mar 17, 2018 10:50 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Total entropy change determining spontaneity
Replies: 3
Views: 219

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 ...
by melissa carey 1f
Sat Mar 17, 2018 10:43 am
Forum: Biological Examples (*DNA Structural Transitions, etc.)
Topic: 9.69
Replies: 1
Views: 391

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...
by melissa carey 1f
Thu Mar 15, 2018 8:20 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Gibbs and Activation Energy
Replies: 4
Views: 285

Gibbs and Activation Energy

Hi! Is there a relationship between Gibbs energy and activation energy? Thanks! :)
by melissa carey 1f
Wed Mar 14, 2018 12:43 pm
Forum: *Free Energy of Activation vs Activation Energy
Topic: 4.29 Green book
Replies: 3
Views: 1003

Re: 4.29 Green book

this can be seen in the arrhenius equation:

https://www.chemguide.co.uk/physical/basicrates/arrhenius.html
by melissa carey 1f
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: 242

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.
by melissa carey 1f
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: 757

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.
by melissa carey 1f
Mon Mar 05, 2018 12:42 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: rate order vs contribution to overall rate
Replies: 3
Views: 116

Re: rate order vs contribution to overall rate

How does the overall rate indicate these relationships?
by melissa carey 1f
Mon Mar 05, 2018 12:41 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 0 order
Replies: 6
Views: 198

Re: 0 order

How does this graphic representation correlate to the presence of a catalyst?
by melissa carey 1f
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: 831

Re: Endergonic and exergonic free energy reaction profiles?

I believe these terms are used to refer to the same reactions as exothermic and endothermic.
by melissa carey 1f
Wed Feb 28, 2018 12:37 pm
Forum: First Order Reactions
Topic: 15.15
Replies: 4
Views: 136

Re: 15.15

Since the rate increase is linear to reactant concentration increase, it implies it's first order.
by melissa carey 1f
Wed Feb 28, 2018 12:36 pm
Forum: First Order Reactions
Topic: Direct Proportions and First Order
Replies: 5
Views: 162

Re: Direct Proportions and First Order

First order indicates that doubling the reactant concentration doubles the rate because rate = k [A]^1
by melissa carey 1f
Wed Feb 28, 2018 12:34 pm
Forum: Zero Order Reactions
Topic: Half-life of Zero Order [ENDORSED]
Replies: 4
Views: 174

Re: Half-life of Zero Order [ENDORSED]

I thought we only needed to know half-lives for first-order reactions?
by melissa carey 1f
Mon Feb 19, 2018 3:05 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.33
Replies: 1
Views: 117

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
by melissa carey 1f
Mon Feb 19, 2018 3:02 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.51
Replies: 1
Views: 96

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.
by melissa carey 1f
Mon Feb 19, 2018 2:59 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Problem 14.23 (b)
Replies: 1
Views: 87

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.
by melissa carey 1f
Mon Feb 19, 2018 2:57 pm
Forum: Balancing Redox Reactions
Topic: 14.15c
Replies: 2
Views: 131

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!
by melissa carey 1f
Sun Feb 18, 2018 1:02 pm
Forum: Balancing Redox Reactions
Topic: 14.15c
Replies: 2
Views: 131

14.15c

Hi! I was wondering why in the solutions manual potassium is included in the final cell diagram? Thanks!
by melissa carey 1f
Thu Feb 15, 2018 9:12 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Delta G= Wmax
Replies: 8
Views: 419

Re: Delta G= Wmax

Whats the relationship between free energy and max work - are they equal?
by melissa carey 1f
Thu Feb 15, 2018 9:11 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Units for Gibbs Free Energy
Replies: 4
Views: 318

Re: Units for Gibbs Free Energy

When a problem asks for Gibbs Free energy in "kJ" does this mean kJ/mol or just kJ?
by melissa carey 1f
Thu Feb 15, 2018 9:10 am
Forum: Balancing Redox Reactions
Topic: Salt Bridges
Replies: 14
Views: 335

Re: Salt Bridges

In a battery, like a AAA battery, what serves as a salt bridge?
by melissa carey 1f
Wed Feb 07, 2018 7:03 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.83
Replies: 3
Views: 202

Re: 11.83

This isn't what the solution manual says? Can someone explain how to approach this problem?
by melissa carey 1f
Mon Feb 05, 2018 2:23 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge [ENDORSED]
Replies: 4
Views: 585

Re: Salt Bridge [ENDORSED]

What is the porous disk composed of? Does it act differently than the salt bridge in any way?
by melissa carey 1f
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: 268

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!!
by melissa carey 1f
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: 568

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.
by melissa carey 1f
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: 208

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!
by melissa carey 1f
Thu Feb 01, 2018 2:07 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.11 [ENDORSED]
Replies: 3
Views: 146

Re: 9.11 [ENDORSED]

We also use P1/P2 as opposed to V2/V1 since pressure and volume are inversely related. P1V1=P2V2.
by melissa carey 1f
Thu Feb 01, 2018 2:06 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: sign of entropy
Replies: 11
Views: 250

Re: sign of entropy

Additionally, during a process of expansion entropy increases as there are more possible states.
by melissa carey 1f
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: 707

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...
by melissa carey 1f
Tue Jan 23, 2018 4:36 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Irreversible vs. Reversible [ENDORSED]
Replies: 10
Views: 385

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!
by melissa carey 1f
Tue Jan 23, 2018 4:36 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Irreversible vs. Reversible [ENDORSED]
Replies: 10
Views: 385

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!
by melissa carey 1f
Tue Jan 23, 2018 4:32 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 3 Test Topic is endorsed
Replies: 37
Views: 1807

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!
by melissa carey 1f
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: 103

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!
by melissa carey 1f
Tue Jan 16, 2018 7:54 pm
Forum: Phase Changes & Related Calculations
Topic: Steam burning more than water question
Replies: 4
Views: 153

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.
by melissa carey 1f
Tue Jan 16, 2018 7:52 pm
Forum: Phase Changes & Related Calculations
Topic: Types of Systems
Replies: 10
Views: 380

Re: Types of Systems

Is there a type of system which somehow exchanges particles but not heat? Or is this impossible?
by melissa carey 1f
Tue Jan 16, 2018 7:50 pm
Forum: Phase Changes & Related Calculations
Topic: Gas Law
Replies: 2
Views: 119

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.
by melissa carey 1f
Thu Jan 11, 2018 10:15 am
Forum: Phase Changes & Related Calculations
Topic: Exothermic Rxn
Replies: 6
Views: 275

Re: Exothermic Rxn

Is there another way to determine if a reaction can occur spontaneously?
by melissa carey 1f
Thu Jan 11, 2018 10:05 am
Forum: Administrative Questions and Class Announcements
Topic: Constants & Equations Sheet
Replies: 3
Views: 162

Re: Constants & Equations Sheet

Is this sheet posted anywhere so we can start working with it? Thanks!
by melissa carey 1f
Thu Jan 11, 2018 10:01 am
Forum: Administrative Questions and Class Announcements
Topic: Lecture Outline
Replies: 2
Views: 147

Lecture Outline

Does anyone know if there is a schedule posted anywhere which outlines which sections of the book correspond to each lecture? Thanks :)

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