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Homework Help: Amount in mol of compound ions

  1. Dec 19, 2007 #1
    [SOLVED] Amount in mol of compound ions

    This is just a quick question as it has slipped my mind..

    Does anyone know how you would find the mol of a compound ion (ie - SO42- (sulfate ion)), if you are given the mol of the whole compound (in my case it is K2SO4)

    I know to find single ions and atoms (ie of potassium and Oxygen) you just multiply their number by the amount of mol, however i am less sure of the compound ions...

    Do you treat the compound ion, in this case...as having a subscript of 1? therefore you would multiply the amount in mol by 1?

    thank you..
  2. jcsd
  3. Dec 20, 2007 #2


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    I think you have solved your own problem.
  4. Dec 20, 2007 #3
    Yeah i may have...haha

    The problem is...I'm making sure because the answer at the back of my book I know is wrong...So i have nothing to check against
  5. Dec 20, 2007 #4
    what is the actual question?
  6. Dec 20, 2007 #5
    Some dimensional analysis makes it intuitive

    [tex]#mol (K_2SO_4) * \frac{1 mol SO_4}{1 mol K_2SO_4}[/tex]

    That fraction is equal to 1 since there is exactly 1 mol of SO4 in every mol of K2SO4

    The mol K2SO4 cancel out and you have what you're looking for
  7. Dec 20, 2007 #6
    The given question was not worded well

    But i understand now that in a compound such as K2SO4, you would treat SO4^2- as one ion in this compound....therefore you would multiply 1 by the number of mol there is of K2SO4..

    Problem solved.....thanks guys
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