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Homework Help: Mass Spectrometry

  1. Jul 18, 2008 #1
    1. The problem statement, all variables and given/known data

    An organic compound contains some C and H atoms and 1 S atom. Element sulfur, S has 2 isotopes, S-32 ans S-34. Their relative isotopic abundance is 100:4 (or 25:1). On the mass spectrometry graph, how would the peak of M+2 compared to that of M+'s peak?

    2. Relevant equations

    3. The attempt at a solution
    This is a question in Wade Organic Chemistry book. The answer given in the book is that the peak at M+2 is 4% of that of M+'s peak. However, my lecturer points out that the book is wrong. He says that the peak of M+2 should be 104% of that of M+'s peak. Who is correct?

    I think the book is correct. Since the ratio of compound with S-32 and S-34 is 25:1. So I don't see any reason why we need to add 100 to that 4.
  2. jcsd
  3. Jul 22, 2008 #2


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    You are right. Are you sure you heard the lecturer correctly?
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