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Rate Law problems

  1. Mar 2, 2006 #1
    I have given this problem:

    The reaction:
    A--> Products

    Follows the Rate Law, Rate = k[A]^2. When the initial concentration of A is 2.00M, it takes 1 hour for 60% of A to react at 25 celsius. What is the value of the rate constant k at this temp?

    -I try to sub 2.00 into A, and (2.00 * .6)/3600 (in seconds) for rate, but I always get a different answer:bugeye:

    -the answer is suppose to be 2.1*10^-4 M^-1 s^-1

    Many thanks!
  2. jcsd
  3. Mar 3, 2006 #2
    Are you familiar with the equations for 0 order, 1st order and 2nd order reactions? It is possible to mathematically derive them, but it seems like you are usually given them in a data sheet.

    The equation for a 2nd order reaction such as the one you have been given is

    1/[A] = 1/[Ao] +kt

    From there all you need to do is stick in your numbers. You have been given all of the data you need to put numbers in for the initial and final concentration, and are given a time. Got it?
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