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Rate Laws

  1. Nov 21, 2009 #1
    The first-order decomposition of a colored chemical species, X, into colorless products is monitored with a spectrophotometer by measuring changes in absorbance over time. Species X has a molar absorptivity constant of 5.00 x 10^3 cm^ -1 M^ -1 and the path length of the cuvette containing the reaction micture is 1.00 cm. The data from the experiment are given in the table below.
    [X] Absorbance Time(min)
    (M)

    ? 0.600 0.0
    4.00 x 10^ -5 0.200 35.0
    3.00 x 10^ -5 0.150 44.2
    1.5 x 10^ -5 0.075 ?

    a) calculate the initial concentration of the colored species.
    - I got 1.2 * 10 ^ -4 is that right?

    b) calculate the rate constant for the first-order reaction using the values given for concentration and time. Include unites with your answer.
    - I got 0.0314, however I do not know if this is correct and will the units be cm ^ -1 M ^ -1

    c) calulate the number of minutes it takes for the absorbace to drop from 0.600 to 0.075
    how do you do this?
    d) calculate half-life of the reation. Include units with your answer.
    e) http://www.collegeboard.com/prod_downloads/ap/students/chemistry/ap-cd-chem-0607.pdf [Broken]
    question # 3

    I WOULD REALLY APPRECIATE if you help me out, it is really confusing!

    THANKS!
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
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