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Relationship between Atomic PPM and Mole

  1. Sep 10, 2014 #1
    1. The problem statement, all variables and given/known data

    Why does 25 atomic ppm oxygen mean 25 moles of oxygen in 1e6 mole Fe?

    2. Relevant equations

    # = mol*Avo

    3. The attempt at a solution

    I understand the ppm (parts per million) part. Hence why 25 ppm means 25:1e6. What I do not understand is how they go from atomic to moles....

    The only way I can explain it is:

    # = mol*Avo ---> Since Avogadro's number is a constant, the difference between # (atomic) and mol (moles) is just a given ratio (a number), thus you can use either... But then where is the conversion?...
     
  2. jcsd
  3. Sep 10, 2014 #2

    Borek

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    Staff: Mentor

    Not sure what your question is. 25 ppm means 25 atoms per 106 atoms, 25 dozens of atoms per 106 dozens of atoms, 25 thousands of atoms per 106 thousands of atoms, 25*123456789 of atoms per 106*123456789 of atoms and so son. You can plug any number, including Avogadro's constant.

    After all, mole is just an overgrown dozen.
     
  4. Sep 10, 2014 #3

    DrClaude

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    Staff: Mentor

    :rofl:

    And to think I was impressed by a baker's dozen...
     
  5. Sep 12, 2014 #4
    Thanks Borek. So what you're saying is that as long as the ratio is held, the number can be anything (even mole)? I forgot that mole is simply a means of expressing the amount of a chemical substance... just like # of atoms. Whoops.
     
  6. Sep 12, 2014 #5

    Borek

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    Staff: Mentor

    Exactly.
     
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