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Homework Help: Question regarding the rate law of a reaction

  1. Feb 5, 2016 #1
    1. The problem statement, all variables and given/known data
    Data in the table were collected at 300 K for the following reaction:

    A(g) + B(g) → products

    Concentration of A

    Concentration of B

    Initial Rate (M/s)

    Determine the rate law for the reaction.

    2. Relevant equations

    Rate = k[A]^m^n, where m and n are the reaction orders.

    3. The attempt at a solution

    I tried to find the factor [A] increases by for trials 1 and 2, and got the value 0.1. I got a value of 0.103 for the rate that the initial rate changes from trial 1 to 2. From there, I get stuck. I had an equation that I used to try and find the reaction order for [A], but I cant seem to find it anywhere, and any other attempts to find the reaction order give me negative values such as -6, and impossibly large numbers. Please help!

    Also, for some reason I cant see the homework template that keeps getting suggested to me. Is there a pdf download anywhere?
  2. jcsd
  3. Feb 11, 2016 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
  4. Feb 11, 2016 #3
    You have 3 equation in three unknowns, k, m, and n. The easiest way to do this problem is to take the log of both sides of the rate expression:

    log(r) = log(k) + m log(A) + n log B

    You have 3 values of A, 3 corresponding values of B, and 3 corresponding values of R. Substituting these into the above equation will give you 3 linear algebraic equations in the 3 unknowns, log (k), m, and n.
  5. Feb 12, 2016 #4


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    Homework Helper
    Gold Member

    Quite simply, comparing the first two when you decrease the concentration of A by a factor of 10, you decrease the rate by practically a factor of 10. So that is telling you that the reaction is first-order in A. Now how about B?
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