Search found 16941 matches

by Chem_Mod
Thu Mar 14, 2019 8:13 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activated Complex Model
Replies: 1
Views: 31

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: 15

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: 36

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: 25

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: 19

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: 20

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: 19

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: 37

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: 19

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: 27

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: 40

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: 26

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: 22

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: 659

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: 27

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: 31

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: 26

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: 37

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: 31

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: 39

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: 22

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: 30

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: 33

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: 256

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: 256

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: 36

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: 256

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: 84

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: 84

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: 27

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: 577

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: 659

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: 90

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: 56

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.
by Chem_Mod
Wed Mar 13, 2019 2:39 pm
Forum: Administrative Questions and Class Announcements
Topic: Danielle's Office Hours This Fri Canceled
Replies: 1
Views: 38

Danielle's Office Hours This Fri Canceled

I have a final scheduled during my office hours, so I have to cancel them this week. If you have any questions, feel free to email me and we can schedule something.
by Chem_Mod
Wed Mar 13, 2019 1:29 pm
Forum: Administrative Questions and Class Announcements
Topic: Excellence in Chemistry Award 2017-2018
Replies: 1
Views: 65

Excellence in Chemistry Award 2017-2018

This morning Wednesday at 11 am in CS50 Michelle Nguyen received the Excellence in Chemistry Award for the highest combined Chem 14A and Chem 14B score!

Post photos here. Thanks.
by Chem_Mod
Wed Mar 13, 2019 12:56 pm
Forum: Administrative Questions and Class Announcements
Topic: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)
Replies: 179
Views: 5586

Re: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)

Here is the key for last Sunday's worksheet and another worksheet focusing on reaction mechanisms. Full solutions are also given.

Good luck on your final!!!!!! It has been a great quarter!

Best,
K
by Chem_Mod
Wed Mar 13, 2019 12:17 pm
Forum: Student Social/Study Group
Topic: Group photo for lecture 1
Replies: 1
Views: 90

Group photo for lecture 1

Here is the group TA/UA photo with students.
by Chem_Mod
Wed Mar 13, 2019 10:58 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6th edition 14.97
Replies: 1
Views: 23

Re: 6th edition 14.97

Because you have 2 moles of HF in your standard reduction potential equation. In Ka expression, it is the dissociation of 1 mole of HF.
by Chem_Mod
Wed Mar 13, 2019 8:32 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Week 9 Worksheet (2E,I,K)
Replies: 13
Views: 577

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

Elle_Mendelson_2K wrote:Where can we find week tens worksheet?


Hi Elle,

I have email the worksheet 10 and will upload full version with answer key after discussion.
by Chem_Mod
Tue Mar 12, 2019 3:31 pm
Forum: Administrative Questions and Class Announcements
Topic: Yekan Final review slides and solutions 0312
Replies: 8
Views: 206

Yekan Final review slides and solutions 0312

The slides are questions and the pdf is the solution
by Chem_Mod
Mon Mar 11, 2019 11:02 pm
Forum: General Rate Laws
Topic: what if
Replies: 3
Views: 36

Re: what if

For each given reaction, there would be only one unique rate law. Thus, the rate law of a reaction cannot sometimes be first order, sometimes second order. In addition, you cannot determine directly from the written reaction what order it is. It can only be determined by experiment.
by Chem_Mod
Mon Mar 11, 2019 6:12 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-equilibrium approach
Replies: 1
Views: 38

Re: Pre-equilibrium approach

Try the end of chapter problems 7.11 and 7.23
by Chem_Mod
Mon Mar 11, 2019 5:55 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7D1 (7th edition)
Replies: 1
Views: 37

Re: 7D1 (7th edition)

Did you use ?
by Chem_Mod
Mon Mar 11, 2019 5:45 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: example 7C1
Replies: 1
Views: 54

Re: example 7C1

This example does not use the approximation that the rate is only determined by the slow step. They instead use the steady-state approximation and then the mathematical approximation that \frac{1}{x+y}\approx\frac{1}{x} if x>>y However, if you use the the approximation that the rate is only determin...
by Chem_Mod
Mon Mar 11, 2019 5:31 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6.65 7th edition
Replies: 1
Views: 41

Re: 6.65 7th edition

There may be a mistake in the solutions manual. Use , which is found in section 6N.3
by Chem_Mod
Mon Mar 11, 2019 5:28 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Homework Question
Replies: 2
Views: 81

Re: Homework Question

On closer inspection, this appears to be a mistake. Use
by Chem_Mod
Mon Mar 11, 2019 4:46 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: mmol vs mol
Replies: 6
Views: 52

Re: mmol vs mol

No as long as your conversion is correct!
by Chem_Mod
Mon Mar 11, 2019 4:40 pm
Forum: Email Notification (click for details)
Topic: Kinetics Questions from Morris' Review
Replies: 1
Views: 139

Kinetics Questions from Morris' Review

Attached are practice questions from my kinetics review session on March 10th 2019.
by Chem_Mod
Mon Mar 11, 2019 4:36 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Activated complex
Replies: 3
Views: 45

Re: Activated complex

No, you will not be expected to know how to draw the transition states of reactions.
by Chem_Mod
Mon Mar 11, 2019 4:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Increasing oxidizing power
Replies: 2
Views: 18

Re: Increasing oxidizing power

Something that is more likely to be reduced will have higher oxidizing power.
by Chem_Mod
Mon Mar 11, 2019 4:28 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Determination of Reaction Rates
Replies: 1
Views: 41

Re: Determination of Reaction Rates

For all of them you can use a spectroscopic technique. but for 2. you can also measure the pH change and for 4. you can use the spectroscopic technique for the visible region.
by Chem_Mod
Mon Mar 11, 2019 4:24 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Selective discharging of ions
Replies: 1
Views: 20

Re: Selective discharging of ions

It is the ones that have the more positive reduction potentials, given by the Eo values.
by Chem_Mod
Mon Mar 11, 2019 4:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Indicators
Replies: 1
Views: 29

Re: Indicators

The acid and its conjugate base have different colors. At low pH values the concentration of H+ is high and so the equilibrium position lies to the left. The equilibrium solution has a specific color A. At high pH values, the concentration of H+ is low - the equilibrium position thus lies to the rig...
by Chem_Mod
Mon Mar 11, 2019 4:22 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: For question 7.29
Replies: 1
Views: 29

Re: For question 7.29

We do not cover radicals in this class. Syllabus will be updated today to remove this homework question from the list. Have a good day.
by Chem_Mod
Mon Mar 11, 2019 4:21 pm
Forum: Balancing Redox Reactions
Topic: 6L.7
Replies: 1
Views: 23

Re: 6L.7

The half reaction with the higher reduction potential would be the cathode. The other half reaction is the anode.
by Chem_Mod
Mon Mar 11, 2019 4:19 pm
Forum: Second Order Reactions
Topic: Question 15.9 Part C (Sixth Edition) [ENDORSED]
Replies: 1
Views: 34

Re: Question 15.9 Part C (Sixth Edition) [ENDORSED]

Refer to the differential rate law form rate=k[reactant]^order

Rate is always in units of M/s.
Depending on the overall order of the reaction, you may have 1, M, M^2, etc. The units of k would be whatever gives you rate in units of M/s.
by Chem_Mod
Mon Mar 11, 2019 4:19 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Mechanisms
Replies: 2
Views: 34

Re: Reaction Mechanisms

It may help to draw a reaction profile using the given information. Remember that you are looking for the overall difference between reactants and products.
by Chem_Mod
Mon Mar 11, 2019 4:18 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-Equilibrium vs Steady-State Approach
Replies: 2
Views: 31

Re: Pre-Equilibrium vs Steady-State Approach

The steady-state approximation is more accurate and more useful for complex situations, but the math is more difficult which is why we do not use it.
by Chem_Mod
Mon Mar 11, 2019 4:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Determining stability based on K
Replies: 1
Views: 28

Re: Determining stability based on K

The equilibrium constants will tell you if reactants or products are favored but will not tell you specifically which reactant is more stable.
by Chem_Mod
Mon Mar 11, 2019 4:15 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Large Ea
Replies: 2
Views: 25

Re: Large Ea

For an ENOURMOUSLY large Ea the E of the transition state needs to be overwhelmingly larger than the E of the reactants. This is achieved by stable (Strong) reactant bonds and very unstable / high E bonds in the transition state. In theory every reaction is possible to proceed but in practice the li...
by Chem_Mod
Mon Mar 11, 2019 4:15 pm
Forum: *Free Energy of Activation vs Activation Energy
Topic: Factors
Replies: 1
Views: 28

Re: Factors

We do not go into detail on this, but anything that may affect the transition state, or original initial energy of the reactants can affect the activation energy.
by Chem_Mod
Mon Mar 11, 2019 4:14 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E
Replies: 1
Views: 20

Re: E

E o is the potential at the standard conditions, so this standard potential would have one value as long as these conditions are met. E can change based on what Q is, just like how delta G can change based on what Q is. If E > E o , the reaction proceeds forward spontaneously to reach equilibrium un...
by Chem_Mod
Mon Mar 11, 2019 4:14 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Large Ea
Replies: 2
Views: 25

Re: Large Ea

Activation energy can make a reaction occur extremely slowly to the point that the reaction will not proceed. Note also that endergonic reactions will never proceed unless there is energy input.
by Chem_Mod
Mon Mar 11, 2019 4:13 pm
Forum: Experimental Details
Topic: Which Experiment to Use
Replies: 1
Views: 16

Re: Which Experiment to Use

You want to pick reactions that hold other reactant concentrations constant.
by Chem_Mod
Mon Mar 11, 2019 4:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Multiplying K by a factor
Replies: 1
Views: 23

Re: Multiplying K by a factor

If you are doing so for all the concentrations of all reactants and products involved in the equilibrium expression, then yes.
by Chem_Mod
Mon Mar 11, 2019 4:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Maxwell Boltzmann Distribution Curve
Replies: 1
Views: 22

Re: Maxwell Boltzmann Distribution Curve

Increasing the temperature will cause the Maxwell Boltzmann Distribution Curve to shift right. As the temperature of the molecules increases, the distribution also flattens out. Because the molecules have greater energy at higher temperature, the molecules are moving faster, so the activation energy...
by Chem_Mod
Mon Mar 11, 2019 4:12 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation Application?
Replies: 1
Views: 13

Re: Arrhenius Equation Application?

It gives the dependence of other parameters that affect the rate constant.
by Chem_Mod
Mon Mar 11, 2019 4:11 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-equilibrium approach
Replies: 1
Views: 17

Re: Pre-equilibrium approach

You can use the pre-equilibrium approach to find the overall rate law if you know which step is slow.
by Chem_Mod
Mon Mar 11, 2019 4:10 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: pre equilbrium constants
Replies: 1
Views: 22

Re: pre equilbrium constants

Correct
by Chem_Mod
Mon Mar 11, 2019 4:09 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Frequency Factor
Replies: 2
Views: 24

Re: Frequency Factor

The arrhenius equation uses the frequency factor. Usually it will be given, or enough information will be given to find it.
by Chem_Mod
Mon Mar 11, 2019 2:02 pm
Forum: General Rate Laws
Topic: Collision Theory
Replies: 1
Views: 14

Re: Collision Theory

A higher order reaction means more molecules are colliding simultaneously in the rate determining step, which is less likely
by Chem_Mod
Mon Mar 11, 2019 1:48 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Rate vs. Initial Rate
Replies: 4
Views: 46

Re: Rate vs. Initial Rate

The rate law relates the rate to the concentrations, so the initial rate depends on the initial concentrations.
by Chem_Mod
Mon Mar 11, 2019 1:45 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies in the Gas Phase
Replies: 1
Views: 21

Re: Bond Enthalpies in the Gas Phase

Calculating the enthalpy of a reaction using average bond enthalpies is already an approximation, so it usually doesn't matter as long as the reactant and product are both in the same phase.
by Chem_Mod
Mon Mar 11, 2019 1:36 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: k in Lavelle's Lecture
Replies: 1
Views: 18

Re: k in Lavelle's Lecture

The rate constant for the overall reaction is a combination of the rate constants for elementary steps. After calculating the overall rate law based on the proposed mechanism, we can compare it to the experimentally-determined rate law to get the overall k in terms of k's for the elementary steps.
by Chem_Mod
Mon Mar 11, 2019 1:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Combining K Values in 11.39
Replies: 1
Views: 30

Re: Combining K Values in 11.39

Suppose you have K 1 for A \rightleftharpoons B and K 2 for B \rightleftharpoons C Then by definition, K_1 = \frac{[B]}{[A]} and K_2 = \frac{[C]}{[B]} So if you want to know K 3 for A \rightleftharpoons C , which by definition is K_3 = \frac{[C]}{[A]} , you can multiply K 1 and K 2 to get K_3 = K_1K...
by Chem_Mod
Mon Mar 11, 2019 1:07 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6.63 7th edition
Replies: 1
Views: 32

Re: 6.63 7th edition

It would probably be more accurate to write E_{cell} = E_{cell}' - \frac{RT}{nF}ln [H^+] The fact that it is calibrated with a buffer solution is only important because buffer solutions have relatively constant, known pH. A pH meter usually includes both electrodes: one reference electrode and o...
by Chem_Mod
Mon Mar 11, 2019 10:40 am
Forum: Student Social/Study Group
Topic: Professor Lavelle's OH
Replies: 2
Views: 169

Re: Professor Lavelle's OH

W: 4-5pm F: 4-5pm Many students ask me questions at the end of every lecture (which is an additional 9 times a week). As you can see I am also online with office hours every day on Chemistry Community. My physical office hours this week are mainly for admin questions as there are so many review sess...
by Chem_Mod
Mon Mar 11, 2019 10:34 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: What to plug in for Q? [ENDORSED]
Replies: 1
Views: 57

Re: What to plug in for Q? [ENDORSED]

In the Nernst equation as long as one uses standard units (molarity for concentration and bar for pressure) then no unit conversions are needed.

Since there is a ~1% difference between 1 bar and 1 atm, we are also accepting using molarity for concentration and atm for pressure.
by Chem_Mod
Sun Mar 10, 2019 10:18 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: 6th edition, 14.119
Replies: 1
Views: 26

Re: 6th edition, 14.119

In the first stage, Au becomes Au(CN)2 - in the anode and O2 + H2O become OH- in the cathode,
In the second stage, Zn becomes Zn(CN)4 2- in the anode and Au(CN)2- becomes Au in the cathode.
by Chem_Mod
Sun Mar 10, 2019 3:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Review Worksheet (Sunday 3-4)
Replies: 2
Views: 193

Re: Review Worksheet (Sunday 3-4)

Answer key attached.
by Chem_Mod
Sun Mar 10, 2019 2:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Review Worksheet (Sunday 3-4)
Replies: 2
Views: 193

Review Worksheet (Sunday 3-4)

Hi,

Attached please find review worksheet (Equilibrium and Acid Base).

-Joyce
by Chem_Mod
Sun Mar 10, 2019 1:34 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Week 9 Worksheet (2E,I,K)
Replies: 13
Views: 577

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

Additional problems answer key attached.

-Joyce
by Chem_Mod
Sun Mar 10, 2019 11:48 am
Forum: Administrative Questions and Class Announcements
Topic: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)
Replies: 179
Views: 5586

Re: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)

Sorry for the delay in this week's worksheet! Didn't realize my last post didn't go through. This week we are reviewing integrated rate laws and if time permits, I will introduce reaction mechanisms. On Wednesday I will post a last worksheet for reaction mechanisms since I won't be seeing you next w...
by Chem_Mod
Sun Mar 10, 2019 10:12 am
Forum: Administrative Questions and Class Announcements
Topic: Nathan's Review Session Problems + Solutions
Replies: 1
Views: 202

Nathan's Review Session Problems + Solutions

Hi everyone! As I mentioned in my review session yesterday, here are the problems I went over with their corresponding solutions. I think the problems cover a lot of the topics in Thermochemistry/Thermodynamics but by no means do they cover everything! They are meant to serve as an additional resour...
by Chem_Mod
Sat Mar 09, 2019 8:39 am
Forum: Administrative Questions and Class Announcements
Topic: Yekan Discussion slides (1B, 1H, 1J)
Replies: 9
Views: 456

Re: Yekan Discussion slides (1B, 1H, 1J)

Does anyone know how to solve the very last question (labeled Question #1) on Yekan's slides for week 8? It's the one on half life but idk what equation he used to solve for the number of days. There is no real equation, what you need is to figure out how many half-live cycles it takes to get 3g fr...
by Chem_Mod
Sat Mar 09, 2019 12:02 am
Forum: General Science Questions
Topic: 14BL [ENDORSED]
Replies: 3
Views: 304

Re: 14BL [ENDORSED]

Chemical equilibrium and acids and bases.
by Chem_Mod
Fri Mar 08, 2019 8:17 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Industrial on Final? [ENDORSED]
Replies: 1
Views: 264

Re: Industrial on Final? [ENDORSED]

What I cover in class should be known.

Otherwise I'll give the reactions, details, etc.
by Chem_Mod
Fri Mar 08, 2019 3:28 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Week 9 Worksheet (2E,I,K)
Replies: 13
Views: 577

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

Typo on worksheet last page:

Column name should be : [A]_0; [B]_0; [C]_0.

- Joyce
by Chem_Mod
Fri Mar 08, 2019 2:44 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Week 9 Worksheet (2E,I,K)
Replies: 13
Views: 577

Week 9 Worksheet (2E,I,K)

Hi all,

Attached please find the discussion notes and the answer key for worksheet9.

Try to do additional problems on last page and I will post the answer for for these two problems by Sunday.

Have a great weekend!

Best,
Joyce
by Chem_Mod
Fri Mar 08, 2019 9:49 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration cell textbook question 6N. 3A self test [ENDORSED]
Replies: 3
Views: 803

Re: Concentration cell textbook question 6N. 3A self test [ENDORSED]

Remember in class I discussed: R ---> P [R] concentration is higher in a concentration cell [P] concentration is lower in a concentration cell Also, The Ag + (aq) is forming (increasing) on the left (in the cell diagram) and therefore the product. The Ag + (aq) is decreasing on the r...
by Chem_Mod
Fri Mar 08, 2019 7:50 am
Forum: Second Order Reactions
Topic: graph
Replies: 2
Views: 30

Re: graph

If 1/concentration vs time is a straight line, then the reaction is second order. Otherwise, if the ln[conc] vs time is linear, the reaction is 1st order.
by Chem_Mod
Fri Mar 08, 2019 1:55 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7 part a 7th edition
Replies: 1
Views: 31

Re: 6L.7 part a 7th edition

If you look at the half reaction with AgBr, the Ag there should be in a solid state, not an aqueous. Thus, we need the Ag+ half reaction.
by Chem_Mod
Fri Mar 08, 2019 1:44 am
Forum: Second Order Reactions
Topic: Half Lives
Replies: 1
Views: 30

Re: Half Lives

It's hard to compare across different orders, as half-lives are measured in different ways.
by Chem_Mod
Fri Mar 08, 2019 1:41 am
Forum: General Rate Laws
Topic: 15.5
Replies: 2
Views: 43

Re: 15.5

Here's a hint:
Screen Shot 2019-03-08 at 1.40.32 AM.png

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