k with more than one reactant

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

k with more than one reactant

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

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.