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Help Determining the Activation Energy

  1. Jul 25, 2005 #1
    This question comes from a study guide and I can't get it. Any help would be greatly appreciated.


    A number of experiments were performed to determine the effect of the temperature on the rate constant, k, for the reaction X + Y --> Z which had been determined to be first order in X. The data are shown below

    Temperature °C.......k (the rate constant)
    0 ........................ 0.010
    25....................... 0.084
    40....................... 0.129
    60....................... 0.176


    From this data, determine the value of the activation energy for the reaction.
     
    Last edited: Jul 25, 2005
  2. jcsd
  3. Jul 25, 2005 #2
    what do the k (s-1) mean? It is not too clear to me

    can you write out the rate law for the reaction?
    how can you use the arrhenius equation here?
     
  4. Jul 25, 2005 #3
    I fixed the format a little, sorry about that. This was the exact question given. The answer given is 30.3 Joules. I have tried everything and can't get an answer close to it. I know that we are supposed to use Arrenhuis's equation and something about a slope of a graph. I just can't put everything together.
     
  5. Jul 25, 2005 #4
    Ahh much better now. The Arrhenius eq. which you probably have seen before is

    k=Ae^-(Ea/RT).

    What happens when you take the natural log of both sides?
    you get from simple algebra-

    lnK=-(Ea/RT) + lnA

    Doesn't this look exactly almost like y=mx+b??? (here y is the lnk, m is -Ea/R, and x is 1/T) which means this equation is a straight line.

    The variables are lnk, and 1/T so if you plot lnk vs. 1/T you will get a straight line. It should be clear how to find Ea now.

    MAKE SURE YOU ALWAYS ALWAYS WORK IN SI UNITS! Make sure to use kelvins,joules, etc.
     
  6. Jul 25, 2005 #5
    Help Determining the Activation Energy Reply to Thread

    Ahh, yes that's what I was missing. Thank you very much for helping me out!
     
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