CHEMISTRY COMMUNITY

Ammarah 2H

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!

Ammarah 2H

I believe they are getting that because -0.59 is equal to ln(k1/k2)!

Ammarah 2H

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...

Ammarah 2H

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!

Ammarah 2H

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!

Ammarah 2H

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).

Ammarah 2H

In 23 part c and 29 part a, why do we take the initial concentration of A and subtract the moles times [B]?

Ammarah 2H

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?

Ammarah 2H

I believe that orders of 3+ are uncommon and then the other orders are more common!

Ammarah 2H

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!

Ammarah 2H

I was stuck too and I keep getting 2649813.982. Is that what you’re getting as well?

Ammarah 2H

For part b, why does n=2 instead of 1?

Ammarah 2H

And also: if the system was not at constant pressure, would we need more information to solve it?

Ammarah 2H

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?

Ammarah 2H

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.

Ammarah 2H

So do we just assume that delta H is positive?

Ammarah 2H

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!

Ammarah 2H

You can find the specific heat values on pg. 269 (table 8.2)!

Ammarah 2H

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.

Ammarah 2H

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.

Ammarah 2H

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).

Ammarah 2H

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.

Ammarah 2H

Are the bond enthalpies for the diatomic molecules accurate or are they also averages?

Ammarah 2H

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?

Ammarah 2H

How do you know that the work is a positive value for #47?

Ammarah 2H

How do you do part C and D? Thank you!

Ammarah 2H

So just for clarification, if heat is absorbed by the system, is the value always negative?

Ammarah 2H

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.

Ammarah 2H

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...

Ammarah 2H

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?

CHEMISTRY COMMUNITY

Search found 30 matches

Re: graphs

Re: 15.63

Re: 15.89

Re: 15.17

Re: Dividing rate laws

Re: 15.17

15.23 & 15.29 [ENDORSED]

Re: 15.15 [ENDORSED]

Re: Zero order common?? [ENDORSED]

Re: Metal on ends of galvanic cell

Re: 14.47 a

14.35

Re: Midterm Review from Class

Midterm Review from Class

Re: Derivation

Re: 9.65

9.65

Re: 8.19

Re: 9.13

Re: Homework 9.5 [ENDORSED]

9.13

Re: 8.75 part b

Re: Bond Enthalpies

Positive and Negative Signs 8.21

8.47

Ch. 8 #67

Re: Q 8.13

Re: Homework Problem 8.21

Re: Homework Problem 8.21

#39 from Chapter 8