## Search found 23 matches

Sun Mar 18, 2018 4:01 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Cell Potential for Concentration Cells
Replies: 1
Views: 189

### Cell Potential for Concentration Cells

Is the standard potential difference for a concentration cell O V? And if so, why?
Sun Mar 18, 2018 3:56 am
Forum: Balancing Redox Reactions
Topic: Winter 2011 Final Exam- Q3A
Replies: 1
Views: 275

### Re: Winter 2011 Final Exam- Q3A

First you write out the half-reactions. MnO2(s) -> MnO4^2-(aq) ClO-(aq) -> Cl- Then you balance the elements Mn and Cl. Once they're balanced, you balance the O atoms using H2O and the H atoms using OH-. Then you balance the charges by adding electrons, multiple by factors until the amount of electr...
Sun Mar 18, 2018 3:48 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Phase changes and entropy
Replies: 5
Views: 513

### Re: Phase changes and entropy

Since phase changes are typically given in delta H Fusion, etc. it's better to make that connection between delta H and q.
Sun Mar 18, 2018 3:44 am
Forum: General Rate Laws
Topic: The Collision Model and Activated Complex Model
Replies: 3
Views: 486

### Re: The Collision Model and Activated Complex Model

An activated complex consists of two molecules that are in a "transition state" meaning they can continue to form a new molecule or they can break apart again. Whether they form a new product or not depends on the amount of energy accumulated from their collision (if it's at least equal to...
Sun Mar 18, 2018 3:31 am
Forum: General Science Questions
Topic: Extensive and Intensive
Replies: 1
Views: 344

### Re: Extensive and Intensive

Specific heat capacity is intensive.
Sun Mar 18, 2018 2:03 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre equilibrium approach
Replies: 1
Views: 281

### Re: Pre equilibrium approach

On one of the previous finals (Winter, 2015) it specified that the pre-equilibrium approach should be used. However, that may not be the case for today's exam.
Sun Mar 18, 2018 1:59 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration Cells
Replies: 2
Views: 308

### Re: Concentration Cells

The higher concentration ion would be the cathode, assuming it's on the right. In the book on page 589, it states that if the concentration of the left-hand electrode ions is less than the concentration of the right-hand electrode ions and the potential difference, E, is positive, then the right-han...
Sun Mar 18, 2018 1:51 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Winter 2015 Final 1B
Replies: 1
Views: 248

### Re: Winter 2015 Final 1B

Yes, this answer is correct. The answer should have only 3 significant figures, and using 25*C gives 4390*C when rounded off.
Sun Mar 18, 2018 1:48 am
Forum: *Identifying Primary, Secondary, Tertiary, Quaternary Carbons, Hydrogens, Nitrogens
Topic: Functional Groups
Replies: 1
Views: 520

### Functional Groups

Are we just expected to learn how to identify functional groups and draw their line structures for the final?
Sat Mar 17, 2018 10:03 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Final Winter 2013
Replies: 3
Views: 363

### Re: Final Winter 2013

The number 4 is the moles of electrons being transferred in the reaction. This number can be determined by looking at the number of electrons present in the half reactions, or by looking at the oxidation numbers of the reactants and products. For the products the Iron has a plus 4 charge and the OH ...
Sat Mar 17, 2018 9:55 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.51
Replies: 2
Views: 338

### Re: 15.51

Yes, the rate law is based on the rate determining step/slow step. It's second order because it depends on the concentrations of two different elements ([NO] and [Br2]) making it bimolecular.
Sat Mar 17, 2018 9:51 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.85 b
Replies: 1
Views: 248

### Re: 15.85 b

The catalyst can be included in the overall reaction equation but it will cancel out in the end. In this case the overall equation is I+I->I2
Sat Mar 17, 2018 8:30 pm
Forum: Balancing Redox Reactions
Topic: Half-Reactions of a Reaction with one Reactant
Replies: 1
Views: 200

### Half-Reactions of a Reaction with one Reactant

In example 14.8 on page 586 of the book, for a reaction with one reactant they define one of the half reactions as the overall reaction itself. What is the reasoning behind this? Or, how would you split a reaction with only one reactant into half reactions?
Sat Mar 17, 2018 7:14 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.69
Replies: 1
Views: 244

### Re: 15.69

The question says to assume that all other factors remain unchanged, including A, to simplify the calculation. In reality the A values would be different and I think the book only includes that statement as a reminder of this.
Sat Mar 17, 2018 7:06 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta g equilibrium
Replies: 2
Views: 284

### Re: delta g equilibrium

Yes, ∆G=0 means it is at equilibrium. However, the change in standard Gibbs Free energy would then be: ∆G° = – RT ln K.
Sat Mar 17, 2018 6:48 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.69
Replies: 1
Views: 220

### Re: 15.69

In the solutions manual they skipped a couple of the algebraic steps. After setting up the proportion they cancelled out A which is the same for both reactions. Then they brought exp(-Ea/RT) to the top and added it to get 1000=exp[(Ea/RT)-(Ea,cat/RT)] . You can the natural log of both sides and then...
Sat Mar 17, 2018 11:15 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 2
Views: 182

### Catalysts

If catalysts aren't consumed during a reaction, why don't they show up in the overall balanced reaction such as the one in question 15.71?
Sat Mar 17, 2018 1:21 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate and equilibrium constants
Replies: 3
Views: 240

### Re: Rate and equilibrium constants

No, there are some factors that will affect the rate constant of a reaction but not the equilibrium constant. For example, a catalyst may increase the rate of a reaction, but the equilibrium constant will stay the same. This is because the equilibrium constant is the proportion of the forward and re...
Tue Mar 13, 2018 7:33 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-Equilibrium Method Conditions
Replies: 2
Views: 179

### Pre-Equilibrium Method Conditions

What are the exact conditions that must be met in order to use the pre-equilibrium method besides the reaction not being at equilibrium? Is that the only one?
Mon Mar 12, 2018 3:50 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Elementary Steps of a Reaction
Replies: 1
Views: 158

### Elementary Steps of a Reaction

How can you determine if an elementary step is the slow step of the reaction if it's not already stated? Would you just use an experimentally determined rate law?
Fri Mar 09, 2018 10:45 pm
Forum: General Rate Laws
Topic: Pseudo-Reactions [ENDORSED]
Replies: 2
Views: 289

### Pseudo-Reactions[ENDORSED]

In what instances will we need to use the pseudo-first-order rate law of a reaction versus a second order rate law?
Sat Feb 10, 2018 12:43 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Heat Capacity Units [ENDORSED]
Replies: 1
Views: 140

### Heat Capacity Units[ENDORSED]

In the Self-Test question 9.2B on page 322, the heat capacity is given with degrees Celsius as units. However, to solve the problem the book just changes this value to Kelvins to solve the problem without using an conversion factors. Why are we able to do this?
Tue Jan 23, 2018 8:52 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 3 Test Topic is endorsed
Replies: 37
Views: 2989

### Re: Week 3 Test Topic is endorsed

melissa carey 1f wrote:Will we be tested on memorizing the formulas in section 8.10: A Molecular Interlude: The Origin of the Heat Capacities of Gases? Thanks!

These equations are included on the constants and equations worksheet. We would likely just need to know how to apply them.