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Homework Help: Chemistry; reaction rate - completion

  1. Jan 22, 2010 #1
    Chemistry; reaction rate -- completion

    1. The problem statement, all variables and given/known data
    A first-order reaction is 17% complete after 30 min. How long after the start of the reaction will the reaction be 80% complete?


    2. Relevant equations
    ln[A] = ln[A0] - kt


    3. The attempt at a solution

    [A] = 0.83
    [Ao] = 1.0
    t = 30 min

    k = ln(1/0.83) / 30 = 0.006211 min-1

    t = ln(1.0/0.2) / 0.006211 = 259 min


    This problem is on a practice exam for my upcoming midterm.

    I'm not sure about my choices for [A].

    When the reaction is completed the [A] = 0, is that right?

    ie, [A] starts at 1.0 -- [A0] in this problem -- and goes to 0, right?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jan 22, 2010 #2
    Re: Chemistry; reaction rate -- completion

    oops, when I solved for t I used a different value for [A]

    [A] = 0.2
     
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