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Homework Help: Finding mass based on amu and % abundance

  1. Sep 24, 2008 #1
    1. The problem statement, all variables and given/known data

    Oxygen has 3 isotopes. Oxygen-16 has the amu of 15.995 and its natural percent abundance is 99.759. Oxygen-17 has a mass of 16.995 amu and its natural percent abundance is 0.037. Oxygen-18 has a mass of 17.999 amu and its natural percent abundance is 0.204. What is the average atomic mass of oxygen?

    2. Relevant equations

    I think I forgot these...

    3. The attempt at a solution

    I couldn't remember what the process is supposed to look like to figure this sort of problem out, so I tried to multiply the mass by the percent abundance, but the answers made very little sense. If somebody could help me figure out where I messed up, PLEASE RESPOND!
  2. jcsd
  3. Sep 24, 2008 #2


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    The average atomic mass of an element is much like a simple mixture problem that you learn in first year Algebra such that you can resort directly to percentage contributions formula.

    AverageAMU = 0.99759*16 + 0.00037*17 + 0.00204*18
  4. Sep 24, 2008 #3
    Thank you so much!
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