## Search found 30 matches

Tue Mar 13, 2018 12:12 am
Forum: General Rate Laws
Topic: graphs
Replies: 8
Views: 423

### Re: graphs

They may also say in the problem that a certain type of graph is a straight line, which tells you the order, and therefore which equation to use!
Tue Mar 13, 2018 12:10 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.63
Replies: 3
Views: 266

### Re: 15.63

I believe they are getting that because -0.59 is equal to ln(k1/k2)!
Tue Mar 13, 2018 12:05 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.89
Replies: 2
Views: 204

### Re: 15.89

You want to get the equations to match the given rate. So if you write the rate law for the second step, you'll notice that there is an intermediate in the rate (in this case, N2O2), and you do not want an intermediate in the final rate law. As a result, you look at the first step and write the rate...
Thu Mar 08, 2018 9:47 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.17
Replies: 6
Views: 532

### Re: 15.17

If you take experiments 1 and 4 to try to solve for the order of C, you'll end up getting (700/400)^n = 1. (n is the order you are solving for). Taking the log of 1 is zero, which is why C has to be zero order!
Tue Mar 06, 2018 9:48 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Dividing rate laws
Replies: 1
Views: 170

### Re: Dividing rate laws

It's easier to solve if the bigger values are on top! It shouldn't matter but it is easier to see relationships if the bigger numbers are on the top. So in this case, it would be easier to do experiment 2 divided by experiment 1 since 40 is greater than 20 and 4 is greater than 2!
Tue Mar 06, 2018 9:25 pm
Forum: General Rate Laws
Topic: 15.17
Replies: 4
Views: 304

### Re: 15.17

If you write the rate law, [C] will be to the zero power, meaning that [C] will always be equal to one, meaning it does not change the rate (so it is independent of the rate).
Thu Mar 01, 2018 9:04 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.23 & 15.29 [ENDORSED]
Replies: 2
Views: 220

### 15.23 & 15.29[ENDORSED]

In 23 part c and 29 part a, why do we take the initial concentration of A and subtract the moles times [B]?
Thu Mar 01, 2018 4:35 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.15 [ENDORSED]
Replies: 5
Views: 349

### Re: 15.15[ENDORSED]

For clarification: If the question said that the OH- concentration doubled and the rate quadrupled, would the order with respect to OH- be second order?
Thu Mar 01, 2018 4:27 pm
Forum: Zero Order Reactions
Topic: Zero order common?? [ENDORSED]
Replies: 5
Views: 323

### Re: Zero order common??[ENDORSED]

I believe that orders of 3+ are uncommon and then the other orders are more common!
Wed Feb 21, 2018 9:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Metal on ends of galvanic cell
Replies: 2
Views: 177

### Re: Metal on ends of galvanic cell

You add an intert metal (usually platinum) at the end of there is no solid metal in the equation. The platinum will be the electrode!
Tue Feb 20, 2018 7:20 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.47 a
Replies: 6
Views: 428

### Re: 14.47 a

I was stuck too and I keep getting 2649813.982. Is that what you’re getting as well?
Tue Feb 20, 2018 12:09 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.35
Replies: 2
Views: 194

### 14.35

For part b, why does n=2 instead of 1?
Tue Feb 13, 2018 5:17 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm Review from Class
Replies: 1
Views: 147

### Re: Midterm Review from Class

And also: if the system was not at constant pressure, would we need more information to solve it?
Tue Feb 13, 2018 5:16 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm Review from Class
Replies: 1
Views: 147

### Midterm Review from Class

When we were going over old test questions, in the question about oxygen difluoride reacting with water vapor, how did we know that the system was at constant pressure?
Tue Feb 13, 2018 5:09 pm
Forum: Van't Hoff Equation
Topic: Derivation
Replies: 5
Views: 447

### Re: Derivation

I don't think they'll specifically ask for a derivation, but there are some equations that are not on the formula sheet which we might have to plug things in to achieve.
Thu Feb 08, 2018 8:23 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.65
Replies: 3
Views: 174

### Re: 9.65

So do we just assume that delta H is positive?
Thu Feb 08, 2018 8:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.65
Replies: 3
Views: 174

### 9.65

I understand how to do the problem, but I was just wondering: why do we only have to calculate delta S and not both delta S and delta H? Thank you!
Thu Feb 08, 2018 12:17 am
Forum: Phase Changes & Related Calculations
Topic: 8.19
Replies: 3
Views: 279

### Re: 8.19

You can find the specific heat values on pg. 269 (table 8.2)!
Wed Jan 31, 2018 6:29 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.13
Replies: 5
Views: 333

### Re: 9.13

I believe that the values of C are based off whether the atom is at constant pressure or volume. I think the 7/2 R is for a linear molecule at constant pressure, 3/2 R is for an atom at constant volume, and 5/2 R is for an atom at constant pressure.
Wed Jan 31, 2018 5:21 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Homework 9.5 [ENDORSED]
Replies: 11
Views: 631

### Re: Homework 9.5[ENDORSED]

Is S final - S initial a correct approach for these types of problems? Because you still get the right answer, I'm just not sure if it works for every problem.
Wed Jan 31, 2018 5:15 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.13
Replies: 5
Views: 333

### 9.13

For #13 on the homework, why isn't the C value used instead of R in the calculation for the temperature? (I was looking at the example and they used C, not R).
Wed Jan 24, 2018 5:17 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.75 part b
Replies: 3
Views: 205

### Re: 8.75 part b

I don't know if this will help, but for these problems, I find it easier to include all of the bonds in the calculation! I draw the Lewis structures and then count all the bonds for both the products and reactants. The math works out because the repeated bonds are subtracted out anyways.
Wed Jan 24, 2018 5:10 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 5
Views: 350

### Re: Bond Enthalpies

Are the bond enthalpies for the diatomic molecules accurate or are they also averages?
Wed Jan 24, 2018 12:29 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Positive and Negative Signs 8.21
Replies: 3
Views: 227

### Positive and Negative Signs 8.21

For questions like 8.21 on the homework, how do we know which side will be positive and which will be negative? Is the one with the lower initial temperature always the negative one?
Thu Jan 18, 2018 1:12 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.47
Replies: 1
Views: 141

### 8.47

How do you know that the work is a positive value for #47?
Tue Jan 16, 2018 10:28 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Ch. 8 #67
Replies: 2
Views: 184

### Ch. 8 #67

How do you do part C and D? Thank you!
Tue Jan 16, 2018 10:23 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Q 8.13
Replies: 9
Views: 529

### Re: Q 8.13

So just for clarification, if heat is absorbed by the system, is the value always negative?
Fri Jan 12, 2018 12:01 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework Problem 8.21
Replies: 4
Views: 258

### Re: Homework Problem 8.21

Yes, the final temperature of the water is the same as the final temperature of the copper! It's because they are in the same container.
Thu Jan 11, 2018 3:08 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework Problem 8.21
Replies: 4
Views: 258

### Re: Homework Problem 8.21

I did the same thing as Britney!! But some thing that might help while doing these problems is that specific heat values be found on the table on page 269, and you know that the final temperature will be somewhere in between the final and initial values, since one gains heat while the other loses he...
Thu Jan 11, 2018 2:01 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: #39 from Chapter 8
Replies: 3
Views: 223

### #39 from Chapter 8

On number 39 from chapter 8, the specific heat of water is multiplied with the grams of water present with the final temperature minus the initial. My question is: how do we know when to use the specific heat? Is it always used in problems when they are asking for q?

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