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Homework Help: Beer lambert law

  1. Oct 5, 2009 #1
    1. The problem statement, all variables and given/known data
    The p-nitrophenolate ion absorbs lights at 405nm. A solution that is 74um in the p-nitrophenolate ion was diluted 1 in 2 with water.Absorbance of resulting solution at 405nm was .650. Calculate molar extinction coefficient of the p-nitrophenolate ion at 405nm. Your meant to assume water has no absorbance at 405 nm.

    How do you use the beer lambert law to predict the absorbance at 405nm of a solution that is 11.0mM in the p-nitrophenolate ion, how do you show absorbance has no units

    2. Relevant equations

    3. The attempt at a solution

    .650 = e x 1 x (74/2)??
    dont think im right at all...
  2. jcsd
  3. Oct 5, 2009 #2


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    Science Advisor
    2017 Award

    That's the correct way to setup the equation, but you should include units so that you can get the units of ε correct (ε is usually reported in units of L cm-1 mol-1).
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