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<div class="moz-cite-prefix">On 07/07/13 16:38, wrote:<br>
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<blockquote
cite="mid:C40B2F181831EF44A88CD735258278030261C41B51@MERCERMAIL.MercerU.local"
type="cite">
<pre wrap="">Hey Dr. Pounds,
Can you go over how to come up with a predicted rate law? (With particular reference/example of number 13 in additional problems for chapter 14).
</pre>
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<font face="serif">I really can't go over ALL of this again, but I
can give you the basic pieces</font> as it relates to the problem
you asked about. Remember that we are looking for a mechanism that
is consistent with the experimentally determined rate law. In
coming up with a mechanism we have to specify not only the reactions
for the individual steps and if they come to equilibrium, but also
the relative speed of that step (typically shown off to the right).
Once we have all of these mechanism pieces in place we can derive a
rate law for that mechanism. What I did in the class notes was
demonstrate how we do this. With a mechanism in place the procedure
is:<br>
<br>
1. Find the rate determining step<br>
2. Write a rate law based on the rate determining step ONLY<br>
3. If the rate determining step is not the first step and involves
intermediates, I have to work backwards up the train of individual
steps to replace intermediates with components that are found in the
overall reaction (again, I did this in the example I did in class)<br>
4. Once I have a "derived" rate law from my mechanism that only
involves components from the overall chemical reaction, then I am
done with the "derivation".<br>
<br>
Now -- in problem 13 all I wanted you to do was PICK which of the
individual steps you thought was the rate limiting step and then
derive the rate law based on your choice and see if it matched up
with the experimentally determined rate law. What I tried to
demonstrate in my solution was that it could not be the first step
but rather had to be the second step. This is something you would
have to do using "trial and error". Problem 61 in Burdge (for which
you have solutions in the student solutions manual) is similar to
this.<br>
<br>
<br>
<br>
<pre class="moz-signature" cols="72">--
Andrew J. Pounds, Ph.D. (<a class="moz-txt-link-abbreviated" href="mailto:pounds_aj@mercer.edu">pounds_aj@mercer.edu</a>)
Professor of Chemistry and Computer Science
Mercer University, Macon, GA 31207 (478) 301-5627
<a class="moz-txt-link-freetext" href="http://faculty.mercer.edu/pounds_aj">http://faculty.mercer.edu/pounds_aj</a>
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