k with more than one reactant

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y3chem
Posts: 174
Joined: Fri Sep 20, 2013 3:00 am

k with more than one reactant

Postby y3chem » Mon Feb 17, 2014 2:58 pm

For the equation listed on the bottom of course reader Pg62 it says that we can use
RATE= k[A]^n[B]^m[C]^L=k'[A]^N
and get k by dividing [A]^N
but we are going to do this three times with different reactants serving as the smallest conc reactant, which will probably give us three k values that are different but similar. To get the k for the reaction as a whole, do we use the average k of the three k values?

irisc23
Posts: 237
Joined: Sat Nov 23, 2013 3:00 am

Re: k with more than one reactant

Postby irisc23 » Mon Feb 17, 2014 3:58 pm

You don't use the average of the three, that wouldn't really make sense mathematically when you put it into the equation for the rate law. But since you have

RATE = k[A]n[B]m[C]l = k'[A]n,

then

k[B]0m[C]0l = k'.

If you have already determined n,m,l by repeating the process three times with different limiting reactants, then the above equation gives you the relationship between k and k'. You can choose to use the rate constant for any of the three trials, so long as you use the correct combination of [A]0n, [B]0m, [C]0l. They will all give you the same result, presuming you did the experiment correctly.


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