## Midterm 2016 question 4B

$aR \to bP, Rate = -\frac{1}{a} \frac{d[R]}{dt} = \frac{1}{b}\frac{d[P]}{dt}$

Uma_Rajiyah_2A
Posts: 11
Joined: Wed Sep 21, 2016 2:56 pm

### Midterm 2016 question 4B

How are we able to determine what the rate limiting step is when we're only given the mechanisms the students create?
Thanks.

ntruong2H
Posts: 50
Joined: Sat Jul 09, 2016 3:00 am
Been upvoted: 1 time

### Re: Midterm 2016 question 4B

Uma_Rajiyah_2A wrote:How are we able to determine what the rate limiting step is when we're only given the mechanisms the students create?
Thanks.

Well, if you think about this, you are trying to find the rate law that matches with the one you found from part A. For any of the students' proposed mechanisms, if you set step 1 as the slow step, you will never get a rate law consistent with the one form part A. So the next step you take is to try to see what happens if you set the second step as the slow step and then use the pre equilibrium approach. To see an example of how to do this problem, see my explanation for working through Student A's proposed mechanism here:

viewtopic.php?f=150&t=20624&p=59198&hilit=question+4b&sid=e6b3f804914f16dfa320bf321227ccbe#p59198

Hope this helps!