Search found 17203 matches

by Chem_Mod
Sat Mar 16, 2019 1:30 am
Forum: Student Social/Study Group
Topic: Lyndon's Review Session
Replies: 8
Views: 318

Re: Lyndon's Review Session

viewtopic.php?f=160&t=44659

For material after the midterm
by Chem_Mod
Fri Mar 15, 2019 11:35 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law Problem (8.55 in the Sixth Edition)
Replies: 2
Views: 66

Re: Hess's Law Problem (8.55 in the Sixth Edition)

The second reaction in the question is not balanced, the 3/2 is used to balance the reaction.
by Chem_Mod
Fri Mar 15, 2019 11:29 pm
Forum: Second Order Reactions
Topic: Half-life of Second-Order
Replies: 1
Views: 58

Re: Half-life of Second-Order

I am not sure what that means but you definitely want to know the expression of half-lives for both 0th 1st and 2nd order reactions.
by Chem_Mod
Fri Mar 15, 2019 11:12 pm
Forum: Student Social/Study Group
Topic: Michelle Nguyen Photos
Replies: 1
Views: 105

Re: Michelle Nguyen Photos

These are great Katelin.
Thank you!
by Chem_Mod
Fri Mar 15, 2019 10:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.9) 7th edition [ENDORSED]
Replies: 1
Views: 1255

Re: 4D.9) 7th edition [ENDORSED]

Super long day.

Nothing has a negative density.

The equivalent would be a negative density for water.

-1g/ml it makes no sense.

Similary, there is no negative energy per gram.

Thank you for all the good wishes, hugs, cards, photos, and smiles.

Wishing you all the Best with your finals.
by Chem_Mod
Fri Mar 15, 2019 7:12 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Exam Practice Problem
Replies: 3
Views: 182

Re: Final Exam Practice Problem

Here are the answer keys!

Week 10-1 Workshop Key.docx
(523.29 KiB) Downloaded 40 times

Week 10-2 Workshop Key.docx
(3.66 MiB) Downloaded 46 times
by Chem_Mod
Fri Mar 15, 2019 7:11 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Exam Practice Problem
Replies: 3
Views: 182

Final Exam Practice Problem

Hello Everyone!

Here are my worksheets from my sessions during week 10. They contain questions from most of the chapters that we went through this quarter. Let me know if you have any questions. Good luck studying!

Week 10-1 Workshop.docx
(126.76 KiB) Downloaded 47 times

Week 10-2 Workshop.docx
(2.05 MiB) Downloaded 36 times


Best Wishes,
Cindy Chen
by Chem_Mod
Fri Mar 15, 2019 7:07 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 7th edition 6N.1
Replies: 1
Views: 28

Re: 7th edition 6N.1

I am not sure about other calculation but the n should be 2 because there are two moles of electron transfer.
by Chem_Mod
Fri Mar 15, 2019 6:14 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: modeling enthalpy
Replies: 1
Views: 61

Re: modeling enthalpy

Do you mean the enthalpies of formation of each species or the enthalpies of reaction or the enthalpies of activation? The enthalpy of reaction for one step corresponds to the vertical distance between reactant and the product of that step (either of which could actually be intermediates). Positive ...
by Chem_Mod
Fri Mar 15, 2019 4:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework #115 Ch.8 Ed.6
Replies: 1
Views: 52

Re: Homework #115 Ch.8 Ed.6

dN = N final - N initial. This is a state function.
by Chem_Mod
Fri Mar 15, 2019 4:35 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: problem 7E3
Replies: 1
Views: 39

Re: problem 7E3

Please show us the problem and show your work so we can see where you are struggling and better assist you.
by Chem_Mod
Fri Mar 15, 2019 4:34 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Homework help
Replies: 1
Views: 46

Re: Homework help

Please show us the problem and your work so we can better assist you.
by Chem_Mod
Fri Mar 15, 2019 4:34 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Problem 61 6th Edition
Replies: 1
Views: 33

Re: Problem 61 6th Edition

Please post the question on this platform so that we do not need to reference back to the textbook. Also, which chapter is question 61 refering to.
by Chem_Mod
Fri Mar 15, 2019 4:34 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Homework 6N17
Replies: 1
Views: 33

Re: Homework 6N17

If Q is less than one than one, than there is a drive (energy to be released) to make more products. Please show us the problem so we know exactly where you are struggling and better assist you.
by Chem_Mod
Fri Mar 15, 2019 4:31 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Homework 6N13a
Replies: 1
Views: 33

Re: Homework 6N13a

Please show us the problem so we don't have to reference the text book on this platform.
by Chem_Mod
Fri Mar 15, 2019 4:30 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: problem 6N5a and b
Replies: 1
Views: 40

Re: problem 6N5a and b

Please show us the problem so we don't have to reference the text book on this platform and show your work so we know where you may struggle.
by Chem_Mod
Fri Mar 15, 2019 4:28 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 7th 6.65
Replies: 2
Views: 60

Re: 7th 6.65

Please attempt the problem, show us your work, so we can gage where you may be struggling with it.
by Chem_Mod
Fri Mar 15, 2019 4:26 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Kinetic Energy
Replies: 1
Views: 50

Re: Kinetic Energy

Hint: Is the rate-determining step the fastest or the slowest step?
by Chem_Mod
Fri Mar 15, 2019 4:25 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: homework question
Replies: 1
Views: 44

Re: homework question

Please thoroughly show your work so students do not have to reference the text book.
by Chem_Mod
Fri Mar 15, 2019 4:23 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: solutions manual error?
Replies: 1
Views: 46

Re: solutions manual error?

Please thoroughly show your work so students don't have to reference the text books.
by Chem_Mod
Fri Mar 15, 2019 4:23 pm
Forum: General Rate Laws
Topic: Q 15.29 6th edition
Replies: 1
Views: 38

Re: Q 15.29 6th edition

I have attached a detailed worked out solution. Hope this helps.
by Chem_Mod
Fri Mar 15, 2019 3:54 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6th ed 14.55
Replies: 1
Views: 55

Re: 6th ed 14.55

We have are Ni^(2+), SO4^ (2-), and H2O. Oxidation: 0.5 O2 + 2H + +2e - --> H2O E=0.82 Reduction: SO4 2- + 4H + + 4e - --> H2SO3 + H2O E=0.17 Ni 2+ + 2e - --> Ni E=-0.26 2H2O + 2e - --> H2 + 2OH - E=-0.41 I believe SO4 2- is not included because the solution is neutral Anode: H 2 O --> 0.5O 2 + 2H +...
by Chem_Mod
Fri Mar 15, 2019 3:39 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7E5 Intermediates
Replies: 1
Views: 38

Re: 7E5 Intermediates

An intermediate is formed and then consumed. It does NOT show up in the net equation. On the other hand, an enzyme is present at the beginning and end of a reaction. By the Induced Fit Theory, an enzyme changes its conformation slightly during the reaction, but is unchanged after. Enzymes are regene...
by Chem_Mod
Fri Mar 15, 2019 3:04 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Week 10 Discussion Notes (2E,2I,2K)
Replies: 6
Views: 263

Week 10 Discussion Notes (2E,2I,2K)

Dear all,

Attached please find the worksheet answer key and discussion notes.

Good luck on your finals! ٩(๑>◡<๑)۶

Best,
Joyce
by Chem_Mod
Fri Mar 15, 2019 2:33 pm
Forum: Administrative Questions and Class Announcements
Topic: Yekan Final review slides and solutions 0312
Replies: 8
Views: 282

Re: Yekan Final review slides and solutions 0312

Christine Chen 1H wrote:How do you find the number of moles and V2, V1 for this problem?

Number of moles are from dividing the mass by the molar mass. V2 is the final volume after mixing, which is the sum of volume of the two sides, and V1 is the initial volume which is given for each part (7.6L and 5.3L).
by Chem_Mod
Fri Mar 15, 2019 12:39 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Number 7.31 7th Edition
Replies: 1
Views: 40

Re: Number 7.31 7th Edition

They omit the negative sign in front of the Ea/R so the order of 1/T is flipped.
by Chem_Mod
Fri Mar 15, 2019 12:34 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test 2, Number 6 part b
Replies: 1
Views: 49

Re: Test 2, Number 6 part b

Yes. The more positive, the stronger the oxidation power.
by Chem_Mod
Fri Mar 15, 2019 7:21 am
Forum: Administrative Questions and Class Announcements
Topic: LAST LECTURE
Replies: 1
Views: 86

Re: LAST LECTURE

Yes that is what I said.
by Chem_Mod
Fri Mar 15, 2019 6:41 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Review Session-Thermo-files- Wednesday-Q11-clarification [ENDORSED]
Replies: 10
Views: 327

Re: Review Session-Thermo-files- Wednesday-Q11-clarification [ENDORSED]

You don’t have to necessarily be given a diagram. But it has to be stated in words that it is a constant pressure process while changing T.
by Chem_Mod
Fri Mar 15, 2019 4:51 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: homework
Replies: 1
Views: 51

Re: homework

You will have the Arrhenius equations for the two temperatures and subtract the two. So, at T1: lnk_{1} = ln A - \frac{E_{a}}{RT_{1}} and at T2: lnk_{2} = ln A - \frac{E_{a}}{RT_{2}} . lnA is eliminated when we subtract the two equations and we get lnk_{2} - lnk_{1} =- \frac{E_{a}}{RT_{2}} + \frac{E...
by Chem_Mod
Fri Mar 15, 2019 4:50 am
Forum: General Rate Laws
Topic: Sealed vessel
Replies: 1
Views: 42

Re: Sealed vessel

According to the solutions manual, since the vessel is sealed the masses and concrentartions are proportional. Therefore, any change in mass, causes a proportional change in concentration. So it is uneccesary to take the extra steps and convert the masses to moles and then concentrations when you ca...
by Chem_Mod
Fri Mar 15, 2019 4:49 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Calomel electrode
Replies: 1
Views: 38

Re: Calomel electrode

Calomel electrodes are beyond the scope of this class. What's more important is distinguishing between anodes and cathodes within various types of cells like galvanic or electrolytic.
by Chem_Mod
Fri Mar 15, 2019 4:48 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.35
Replies: 3
Views: 80

Re: 5.35

Please post the entire question.
by Chem_Mod
Fri Mar 15, 2019 4:47 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7D.5
Replies: 1
Views: 43

Re: 7D.5

You will have the Arrhenius equations for the two temperatures and subtract the two. So, at T1: lnk_{1} = ln A - \frac{E_{a}}{RT_{1}} and at T2: lnk_{2} = ln A - \frac{E_{a}}{RT_{2}} . lnA is eliminated when we subtract the two equations and we get lnk_{2} - lnk_{1} =- \frac{E_{a}}{RT_{2}} + \frac{E...
by Chem_Mod
Fri Mar 15, 2019 3:35 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: HW 5I.33 7th edition
Replies: 1
Views: 41

Re: HW 5I.33 7th edition

Please post the entire question.
by Chem_Mod
Fri Mar 15, 2019 1:43 am
Forum: Administrative Questions and Class Announcements
Topic: LYNDON'S PORK RAMEN REVIEW
Replies: 37
Views: 2254

LYNDON'S PORK RAMEN REVIEW

The title is called "Pork Ramen" so that you can search "Pork Ramen" and easily find this post! This is your UA, Lyndon Bui, with information on the much anticipated Pork Ramen Review Session! This review session will feature a second lovely UA, Hannah Chew! This packet covers m...
by Chem_Mod
Thu Mar 14, 2019 11:23 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pseudo 1st order reaction
Replies: 2
Views: 62

Re: Pseudo 1st order reaction

We use pseudo first order reactions when we are studying a reaction with multiple reactants with concentrations that could affect the rate law. For example if the reaction in question is A+B-->P we would design an experiment to find out how the rate changes with the concentrations of each reactant. ...
by Chem_Mod
Thu Mar 14, 2019 11:18 pm
Forum: *Enzyme Kinetics
Topic: Do we need to know enzyme kinetics for the final?
Replies: 1
Views: 60

Re: Do we need to know enzyme kinetics for the final?

Kinetics is fair game.
by Chem_Mod
Thu Mar 14, 2019 11:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Bronsted Neutralization Reaction
Replies: 1
Views: 40

Re: Bronsted Neutralization Reaction

Notice the number of electrons for each set of reactions. This becomes important when calculating deltaGo, since it equals nFEocell. Voltage is an intrinsic property, so as long as the identify of the reaction is the same, the voltage/potential should be the same.
by Chem_Mod
Thu Mar 14, 2019 11:03 pm
Forum: First Order Reactions
Topic: Linear Plots
Replies: 1
Views: 40

Re: Linear Plots

Well, rate would equal k[A]. In this case, k would be the slope, and rate with respect to [A] would be linear.
by Chem_Mod
Thu Mar 14, 2019 10:59 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: given Ecell
Replies: 2
Views: 62

Re: given Ecell

You can think of it that way, but normally the progression of thought is that galvanic/voltaic cells are spontaneous with positive Ecell, whereas electrolytic cells are nonspontaneous with negative Ecell.
by Chem_Mod
Thu Mar 14, 2019 10:57 pm
Forum: General Rate Laws
Topic: Determining rate order
Replies: 3
Views: 43

Re: Determining rate order

You determine the order of one reactant each time so you want to pick the experiments where the only variation is the concentration of the reactant you are studying.
by Chem_Mod
Thu Mar 14, 2019 10:52 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy v. Free Energy of Activation
Replies: 1
Views: 46

Re: Activation Energy v. Free Energy of Activation

It is probably beyond the scope of this class. Free energy of activation contains an entropic term in addition to the enthalpic one. On the other hand, the activation energy doesn't, entropic part is accounted for by the pre-exponential factor A.
by Chem_Mod
Thu Mar 14, 2019 10:46 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.67 6th Edition (Catalyst)
Replies: 1
Views: 39

Re: 15.67 6th Edition (Catalyst)

The idea is that you want to calculate the ratio of the rate constant k. You can use two Arrhenius equations and take the ratio or the solution manual used the law of log which also works
by Chem_Mod
Thu Mar 14, 2019 10:44 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Hmwrk 15.65
Replies: 1
Views: 34

Re: Hmwrk 15.65

To figure out (b), you have to compare the activation energies for the forward and reverse reactions. Exothermic reactions have a larger activation energy for the reverse reaction, whereas endothermic reactions have a larger activation energy for the forward reaction. You then can use this informati...
by Chem_Mod
Thu Mar 14, 2019 10:42 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: k’ and A
Replies: 4
Views: 59

Re: k’ and A

k is the rate constant and A is the collision factor
by Chem_Mod
Thu Mar 14, 2019 10:40 pm
Forum: General Rate Laws
Topic: Questions with different Experiments
Replies: 1
Views: 26

Re: Questions with different Experiments

The reason to run different experiments is to figure out the order with respect to each reactant. After you figure out all the orders, you can plug in data from any experiment to figure out the rate constant k.
by Chem_Mod
Thu Mar 14, 2019 10:38 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Conductivity
Replies: 1
Views: 32

Re: Conductivity

Generally, all the metals are good conductors.
by Chem_Mod
Thu Mar 14, 2019 10:37 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Entropy for irreversible reaction
Replies: 1
Views: 49

Re: Entropy for irreversible reaction

I think you are talking about irreversible free expansion, because it is free expansion, there is no heat transfer.
by Chem_Mod
Thu Mar 14, 2019 10:35 pm
Forum: First Order Reactions
Topic: integrated rate laws
Replies: 3
Views: 43

Re: integrated rate laws

Both of them should work, but usually, the ln one is more convenient in term of doing calculation
by Chem_Mod
Thu Mar 14, 2019 10:24 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: C in a diatomic molecule
Replies: 3
Views: 56

Re: C in a diatomic molecule

Cv is 5/2 R, whereas Cp is 7/2R. Cp = Cv + R always.
by Chem_Mod
Thu Mar 14, 2019 10:21 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: catalyst vs intermediate
Replies: 9
Views: 78

Re: catalyst vs intermediate

A catalyst is used up and regenerated. An intermediate is formed and used up.
by Chem_Mod
Thu Mar 14, 2019 9:19 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Mechanisms
Replies: 2
Views: 56

Re: Reaction Mechanisms

Please give an example of what you saw. Usually, reaction mechanisms are not used to judge if a reaction is endo or exothermic
by Chem_Mod
Thu Mar 14, 2019 9:17 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: DeltaG dependence on equilibrium constant and pressure
Replies: 1
Views: 49

Re: DeltaG dependence on equilibrium constant and pressure

Delta G = -RTlnK, this equation shows the relationship between equilibrium constant and the Gibbs free energy. Meanwhile, the K can bewrite in terms of partial pressure if gases are involved in your reaction.
by Chem_Mod
Thu Mar 14, 2019 8:28 pm
Forum: General Rate Laws
Topic: when to use what
Replies: 1
Views: 35

Re: when to use what

average rate: over some period of time (ex: rate from 30s to 60s)
instantaneous rate: at a specific point in time (Ex: rate at 1s)
"non unique" rate: what is the rate with respect to x reactant or x product
Unique rate: will usually specify
by Chem_Mod
Thu Mar 14, 2019 8:22 pm
Forum: General Rate Laws
Topic: 15.19 6th edition
Replies: 4
Views: 44

Re: 15.19 6th edition

It would help to post your work to see where the error is!
by Chem_Mod
Thu Mar 14, 2019 8:19 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Pseudo Equlibrium
Replies: 2
Views: 40

Re: Pseudo Equlibrium

Be prepared to answer any questions related to lecture notes or homework.
by Chem_Mod
Thu Mar 14, 2019 8:18 pm
Forum: General Rate Laws
Topic: Unique, Instantaneous, and Average Rate
Replies: 1
Views: 34

Re: Unique, Instantaneous, and Average Rate

Instantaneous rate is exactly what it sounds like: at a specific point in time, what is the rate? Average rate, on the other hand: what is the rate over a given period of time? Keep in mind that this is less accurate than instantaneous rate. At each point in time, the rate varies, so taking an avera...
by Chem_Mod
Thu Mar 14, 2019 8:13 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activated Complex Model
Replies: 1
Views: 56

Re: Activated Complex Model

If temperature increases, then k increases. If the rate constant k increases, then Ea decreases. The activation energy is lower, and the activated complex thus has lower energy. Because it's lower in energy, it is less stable.
by Chem_Mod
Thu Mar 14, 2019 8:11 pm
Forum: General Rate Laws
Topic: 6th Edition #15.85
Replies: 1
Views: 39

Re: 6th Edition #15.85

An activated complex is the the structure that occurs when the molecule is at the highest energy along the reaction path (ie the transition state at the top of that curve at Ea). You will not be asked to draw the structure on the exam.
by Chem_Mod
Thu Mar 14, 2019 8:06 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Effect of temp. on rate constants
Replies: 3
Views: 64

Re: Effect of temp. on rate constants

If you have something with a really big activation energy, it needs all the help it can get, so raising the temperature will have a substantial effect on increasing the rate. Conversely, if a reaction has already a low activation energy, the rate is occurring quickly already. Raising the temperature...
by Chem_Mod
Thu Mar 14, 2019 8:04 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Including n or m in "q" Equation
Replies: 1
Views: 49

Re: Including n or m in "q" Equation

Example is 8.25 in the 6th edition. The heat capacity of the calorimeter is q/delta T, which gives us units of kJ/K. If we did an experiment with a new reaction and observed the change in temperature, we could multiply delta T by calorimeter heat capacity to get q (heat transferred). We don't need m...
by Chem_Mod
Thu Mar 14, 2019 8:01 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: exercise 15.65
Replies: 1
Views: 41

Re: exercise 15.65

The equilibrium constant is defined as k/k', which is forward rate / reverse rate. The problem already gives you the rates, which already took into account the order with respect to reactants or products.
by Chem_Mod
Thu Mar 14, 2019 7:58 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 6th edition, 15.89
Replies: 1
Views: 44

Re: 6th edition, 15.89

Begin by writing rate law for each step. You will see none of them match the real rate law, which indicates to you that we must do some "rearranging" of one of our suggested rate laws to match the one in the problem. For step 1: if we assume Step 1 is in equilibrium, then forward and rever...
by Chem_Mod
Thu Mar 14, 2019 7:52 pm
Forum: Experimental Details
Topic: 6th edition, 15.87
Replies: 1
Views: 53

Re: 6th edition, 15.87

The premise of this question is to evaluate which mechanism best describes the reaction. Because mechanism I has two steps, we only look at the rate determining step, which is the slow step. We see that after writing rate laws for mechanism I and II, the only difference is that mechanism II depends ...
by Chem_Mod
Thu Mar 14, 2019 7:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Direction reaction goes
Replies: 2
Views: 63

Re: Direction reaction goes

Since the problem gives you Kc, you must convert moles of the reactants to pressure values (using PV=nRT). Find the reaction quotient, Q, and compare that value to Kc. If the values are equal, then the reaction is at equilibrium. If Q>Kc, then reverse reaction is favored. If Q<Kc, then forward react...
by Chem_Mod
Thu Mar 14, 2019 6:58 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation question
Replies: 2
Views: 44

Re: Arrhenius Equation question

Both values for k would have to be given. You can only solve an equation like this with one unknown.
by Chem_Mod
Thu Mar 14, 2019 6:58 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy
Replies: 1
Views: 62

Re: Entropy

You cannot determine spontaneity from just Delta S alone. However, an increase in overall entropy (system and surroundings combined) usually means the system is thermodynamically favorable.
by Chem_Mod
Thu Mar 14, 2019 6:56 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation and Collision Theory
Replies: 1
Views: 71

Re: Arrhenius Equation and Collision Theory

The Boltzmann distribution is a statistical thermodynamic model that shows how many particles should be at particular energy levels given the average energy level of a group of particles. The Arrhenius equation adopts this model by producing a rate from this statistical probability, the probability ...
by Chem_Mod
Thu Mar 14, 2019 6:54 pm
Forum: Balancing Redox Reactions
Topic: Problem 14.119- Sixth Edition
Replies: 1
Views: 55

Re: Problem 14.119- Sixth Edition

If something is a spectator ion, that means that it will be on both sides of the ionic equation because nothing is chemically happening to it. You would likely not see something this complicated on the final, but should be able to understand the concepts behind it.
by Chem_Mod
Thu Mar 14, 2019 6:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6th edition - self test 12.14A
Replies: 1
Views: 40

Re: 6th edition - self test 12.14A

Your equation should be CH3NH3+ going to CH3NH2 and H+.
by Chem_Mod
Thu Mar 14, 2019 6:46 pm
Forum: Student Social/Study Group
Topic: class pictures
Replies: 15
Views: 842

Re: class pictures

Great. Thank you.

Any additional photos out there?
by Chem_Mod
Thu Mar 14, 2019 6:43 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6.57
Replies: 2
Views: 39

Re: 6.57

Usually the cathode should be whatever has a higher reduction potential, because reducing this species would be more favorable. Many of the solutions in this section are unclear in their reasoning. Having the species with the lower reduction potential be the species that is reduced would make the ov...
by Chem_Mod
Thu Mar 14, 2019 6:43 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalyst in rate law [ENDORSED]
Replies: 1
Views: 45

Re: Catalyst in rate law [ENDORSED]

Catalysts are not included in the rate law equation. It is not concentration dependent.
by Chem_Mod
Thu Mar 14, 2019 6:42 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Does a -E and -G mean that the reverse reaction is spontaneous? [ENDORSED]
Replies: 3
Views: 48

Re: Does a -E and -G mean that the reverse reaction is spontaneous? [ENDORSED]

A negative Gibb's Free Energy means that the reaction is spontaneous and the reverse reaction is nonspontaneous. A -E value means that a reaction is nonspontaneous and the reverse is spontaneous.
by Chem_Mod
Thu Mar 14, 2019 6:40 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Including H2O in Rate Law
Replies: 1
Views: 48

Re: Including H2O in Rate Law

Can you please post the question for easier reference? Water should not generally show in the calculations unless it is a reactant, in which case you should be able to tell based on the reaction equation.
by Chem_Mod
Thu Mar 14, 2019 6:26 pm
Forum: Administrative Questions and Class Announcements
Topic: Picking up 14A final
Replies: 1
Views: 61

Re: Picking up 14A final

3034 Young Hall
by Chem_Mod
Thu Mar 14, 2019 6:23 pm
Forum: Second Order Reactions
Topic: Third Order Reactions [ENDORSED]
Replies: 2
Views: 64

Re: Third Order Reactions [ENDORSED]

Use the identical method I used in class for 1st order and 2nd order.
by Chem_Mod
Thu Mar 14, 2019 6:22 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Initiating, Propagating, Terminating [ENDORSED]
Replies: 1
Views: 36

Re: Initiating, Propagating, Terminating [ENDORSED]

I did not cover chain reactions this quarter.
by Chem_Mod
Thu Mar 14, 2019 6:20 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Liquid Conductors [ENDORSED]
Replies: 1
Views: 53

Re: Liquid Conductors [ENDORSED]

As I mentioned in class:

1) The only conducting liquid (at room temperature) is mercury.
Hg(l) was used in this example because it was part of the redox reaction.

2) Always use the conducting metal as the electrode if the metal is part of the half-reaction.
by Chem_Mod
Thu Mar 14, 2019 5:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: activated complexes [ENDORSED]
Replies: 2
Views: 60

Re: activated complexes [ENDORSED]

No.

I did not cover transition state structures in detail this quarter.
by Chem_Mod
Thu Mar 14, 2019 5:33 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Review Session-Thermo-files- Wednesday-Q11-clarification [ENDORSED]
Replies: 10
Views: 327

Re: Review Session-Thermo-files- Wednesday-Q11-clarification [ENDORSED]

Since 1L of 1M Ba(NO3)2 contains one mole of Ba2+ and 1L of 1MNa2SO4 contains 1mole of (SO4)2- ions, 1 mole of solid BaSO4 is formed in this experiment. So the enthalpy of this reaction is the enthalpy per mole of BaSO4 formed.
by Chem_Mod
Thu Mar 14, 2019 2:26 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Review Session-Thermo-files- Wednesday-Q11-clarification [ENDORSED]
Replies: 10
Views: 327

Re: Review Session-Thermo-files- Wednesday-Q11-clarification [ENDORSED]

Problem 10 asks about the internal energy change of a reaction. When you deal with reactions and also phase changes (which usually happen in reactions), you may assume const T and const P. The T and P are also stated in the problem. If that is the case q_p=deltaH Heat at constant pressure is equal t...
by Chem_Mod
Thu Mar 14, 2019 10:23 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: P-T Graphs
Replies: 2
Views: 68

Re: P-T Graphs

Please, see Edgar's recent post about yesterday review session.

This diagrams for the case of change in entropy are used to illustrate the fact that S is a state function.
by Chem_Mod
Thu Mar 14, 2019 10:20 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Review Session-Thermo-files- Wednesday-Q11-clarification [ENDORSED]
Replies: 10
Views: 327

Review Session-Thermo-files- Wednesday-Q11-clarification [ENDORSED]

Hello everyone, This is Edgar (the TA that the held the thermo review session on wednesday evening) I am uploading the worksheet that I went over along with the solutions. I just wanted to make a clarification on question 11. I added the question about drawing the P-T diagram to a problem on the boo...
by Chem_Mod
Wed Mar 13, 2019 10:35 pm
Forum: Administrative Questions and Class Announcements
Topic: Deadline to post
Replies: 6
Views: 141

Re: Deadline to post

Brandon_Tran_2E wrote:I would try to do it before the final because I remember last quarter we couldn't make posts after it.


Actually it was the Monday after the final.
Why?

Week 10 ended Sunday midnight.

:-)
by Chem_Mod
Wed Mar 13, 2019 10:33 pm
Forum: Administrative Questions and Class Announcements
Topic: Deadline to post
Replies: 6
Views: 141

Re: Deadline to post

As I announced. Each week ends Sunday.

Therefore Week 10 ends Sunday.

When does Sunday end?

Midnight

QED

:-)

Great classes this quarter.
by Chem_Mod
Wed Mar 13, 2019 7:58 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 6th edition 15.67
Replies: 1
Views: 42

Re: 6th edition 15.67

Ea without a catalyst is 125, and with a catalyst is 75. You can plug those values into the Arrhenius equation and take the ratio.
by Chem_Mod
Wed Mar 13, 2019 7:56 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Week 9 Worksheet (2E,I,K)
Replies: 13
Views: 753

Re: Week 9 Worksheet (2E,I,K)

Christine Chen 1H wrote:For problem 2 part a, shouldn't c = 0 and not 1?

You are right it's a typo.

c = 0.
by Chem_Mod
Wed Mar 13, 2019 6:47 pm
Forum: Student Social/Study Group
Topic: class pictures
Replies: 15
Views: 842

Re: class pictures

Great!
Thank you!

Does anyone have a photo of Michelle Nguyen receiving her award?

Any class photos for Lecture 4?
by Chem_Mod
Wed Mar 13, 2019 6:42 pm
Forum: Student Social/Study Group
Topic: Group photo for lecture 1
Replies: 1
Views: 144

Re: Group photo for lecture 1

Great!
Thank you!

Does anyone have a photo of Michelle Nguyen receiving her award?
Any Lecture 4 photos?
by Chem_Mod
Wed Mar 13, 2019 6:39 pm
Forum: First Order Reactions
Topic: pseudo first order [ENDORSED]
Replies: 5
Views: 100

Re: pseudo first order [ENDORSED]

If one of the concentration is extremely large, then its concentration essentially remains unchanged. Thus the concentration for this item could be considered constant and be incorporated into the rate constant. As a result, it will look as if it were only a first order reaction.

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