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Finding the rate equation and rate constant

  1. Jun 5, 2009 #1


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    1. The problem statement, all variables and given/known data

    The dissociation of a compound was studied by performing measurements of
    a quantity X that is proportional to the concentration of the compound. The values of X measured at various times are as follows:

    X--->1.82, 2.01, 2.31, 2.67, 3.80, 5.25
    t/sec----> 521, 617, 749, 873, 1185, 1449

    Use this information to form a rate equation and rate constant.

    2. Relevant equations

    k= (ln {A(t)/A(0)})/t

    3. The attempt at a solution

    Im having a bunch of problems with this question and need a bit of a jump start.

    1) the value of X: I am not given units or anything. It could basically be anything right?

    2) the question states that X is proportional to the concentration of the compound. It also implies that the compound is dissociating. If you noticed, as time goes on, X is increasing. If they are proportional to each other how can the compound dissociate when X is increasing. My only thought is that they are "inversely" proportional and the question just says proportional.

    3) Assuming that X has units of concentration, I went ahead and calculated the rate constant and got virtually all the same values (implying first order reaction) but the values were all negative. This is because X is increasing. Can I safely assume that these values of X are to do with concentration and assume that they are products and therefore use numbers that decrease proportionally to the given values and come up with a positive rate equation?

    Thankyou for your time
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
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