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Chemistry [Spectrophotometry difficult example]

  1. May 15, 2016 #1
    1. The problem statement, all variables and given/known data
    349fce81d2206bdcd2d1a6293b2e70bc.png

    2. Relevant equations
    A=epsilon*l*c

    3. The attempt at a solution
    So I was wondering on how to set up the equations now, since I don't have much information? Which equations should i use to solve the problem?
     
  2. jcsd
  3. May 15, 2016 #2

    Borek

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    Staff: Mentor

    You have all the information needed. Assume the observed absorbance is the sum of individual absorbances.
     
  4. May 15, 2016 #3
    Please help me understand how I should set up the equations!

    91ebaf011f2f50623d16ab8bc7d8c5e0.png

    This is a big questionmark to me, why u should this?
    0.183 = 9970*concentration of Fe + 34*concentration of cupper. Why is 0.183 equal to that?
     
  5. May 15, 2016 #4

    Borek

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    Staff: Mentor

    This is a direct application of the Lambert's Beer law which you wrote in your first post, and the fact that the observed absorbance is a sum of absorbances of copper and iron.

    Assuming there is no copper, can you write formulas for the absorbances of the solution at both wavelengths? Can you do the same for iron? Can you add these values?
     
  6. May 16, 2016 #5
    I still have really difficult! To understand why you add these values!
     
  7. May 16, 2016 #6

    Borek

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    Staff: Mentor

    Which part of the "absorbance is additive" statement is not clear to you?

    If there is more than one substance present in the solution, each absorbs on its own, so the observed total absorbance is a sum of individual absorbances (at least for relatively diluted solutions).
     
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