Determine order of reaction Kaplan subject test 1 #2


Christian predent
7+ Year Member
15+ Year Member
Oct 13, 2003
New Jersey
    So, kaplan show you an easy way to figure out the order of a reaction by simply rewriting the table as small whole number multiples of the smallest entry in each column. What????
    I am refering to chemistry 1 subject test kaplan problem #2 . Does anyone know where they got the 36 from in line 3?? I am talking about the rate of 36. Why does kaplan make things soo complicated:confused:


    Full Member
    10+ Year Member
    Feb 12, 2007
    1. Dental Student
      most people dont have the subject test in front of them so it would be nicer if you type it out...also order of reaction is very easy to do...and you can basically do it in your head....

      so you have
      k[A]^n^m = Rate

      well from the chart just pick one of the reaction that constant measurement and the other not constant. Take the none constant one divide it by each other and do that to rate. and you can easily figure out the power of that. then do it for the next one (there are usually 3 reaction rates in a order problem)....i will throw an example

      [A] Rate
      1) 1 2 2
      2) 1 4 8
      3) 2 4 16

      so lets choose rate 1 and 2 to figure out the order of reaction for B. Since A is constant we can ignore it. and do

      Rate2/Rate1 = 2/1
      which gives you 4 = 2^x, x = 2 so order for reaction is B.
      Note that the real equation is (Rate2/Rate1 = k[A]/k[A]), but since k and [A] are equal we can just cross it out.

      so now lets so order for A...which we can use equation 2 and 3
      Rate3/Rate2 = [A]3/[A]2 which gives you
      2 = 2^x, x= 1

      so then we now know that [A] is a first order and is a second order reaction. The overall equation will be

      Rate = [k][A]^2, and we can simply solve for k by choosing any of the three rates and plugging them in...

      i hope this is what you were asking for....?
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