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Homework Help: Isotope percentages

  1. Aug 29, 2009 #1
    1. The problem statement, all variables and given/known data
    Carbon has two naturally occurring isotopes with the following isotopic masses: 12 (exactly) and 13.003. Calculate the percent natural abundance of carbon-13.

    2. Relevant equations
    I'm not sure if this is right, but here's what I used. I set up a system of two equations, 12x+13.003y=12.0107 (12.0107 being the atomic weight for carbon, obtained from the periodic table) and x+y=1 (because these are the ratios, which will be used to find the percentages).

    3. The attempt at a solution
    I solved for y, since that's the percentage I'm looking for. I don't think I should need to show my work, since it's pretty basic, but I was wondering if this is the right way to go about solving this problem. My answer came out to 1.1%, or 0.011 for y. Is this correct?
  2. jcsd
  3. Aug 29, 2009 #2


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    Staff: Mentor

    Method looks OK and the result seems to be in a correct ballpark.

    Last edited: Aug 29, 2009
  4. Aug 29, 2009 #3
    Thanks Borek, I appreciate the prompt response.
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