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 Posted: Tue Oct 09, 2012 4:01 pm    Post subject: Most of these look fine at first glance, the theory questions seems sound, and the calculations I checked are correct. Which questions in particular do you lack confidence?

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Joined: 07 Oct 2012
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Location: United States
Posted: Tue Oct 09, 2012 7:23 pm    Post subject:

 GrahamKemp wrote: Most of these look fine at first glance, the theory questions seems sound, and the calculations I checked are correct. Which questions in particular do you lack confidence?

Fellow classmates have told me Question 8, 22, and 24 were wrong, that it is suppose to be 6.36 torr, an increase in k occurs, which results in a faster rate, and Rate = k [A2]1/2[B]. Supposedly, my answer 8.36 was in atm, and it was suppose to be in torr. I found the second one in the book. #24, I don't particularly understand, knowledge that I have of it is that the slow step is the rate determining step, that answer, I don't particularly understand. My professor said there might be an error in one of the questions, so i might of gotten one more right. That leaves one more question wrong unaccounted for. I can't guess as to which one in particular that I am lacking confidence in though. So I guess if you can explain #24, that would be great.

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Joined: 19 Mar 2012
Posts: 391
 Posted: Tue Oct 09, 2012 7:49 pm    Post subject: The slow step is the rate determining step, but that means you ignore the subsequent steps. The rate is the combination of all elementary steps up to and including the bottleneck (and cancelling intermediates). A2 + 2 B = 2 AB ======== {A2 -> 2 A}, k1 fast {A + B -> AB}, k2 slow Rate = 1/2 d[AB]/dt = k2 [A][B] [A] can't be in the answer, as it's an intermediate, but can be derived from [A]^2 = k1 [A2]. Rate = 1/2 d[AB]/dt = k1k2 [A2]^(1/2)[B]
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