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Quick moles problem

  1. Jul 10, 2009 #1
    1. The problem statement, all variables and given/known data

    If you have 4.5 x 1020 molecules of SnO2, how many moles of O do you have?


    3. The attempt at a solution

    I'm really getting the hang of moles lately but what is bothering me in this question is 4.5 x 1020 molecules of SnO2.

    If it was one molecule, you would have 2 moles of O yes?
    Therefore in 4.5 x 1020 molecules, you have 4.5 x 1020 multiplied by 2? But that doesn't give me the correct answer.
     
  2. jcsd
  3. Jul 10, 2009 #2

    symbolipoint

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    Simple unit conversion and seeing the ratio of items. You need to know the meaning of a mole.
     
  4. Jul 10, 2009 #3
    Would I be right in saying that there would be 2 mols of O in ONE molecule of SnO2? I think so. So that would be 2 x Avogadros #.

    Therefore in 4.5 x 1020 molecules of SnO2, there should be 2 mols of O x 4.5 x 1020 molecules? I know thats not right though. Where am I going wrong.
     
    Last edited: Jul 10, 2009
  5. Jul 10, 2009 #4

    Borek

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    No. There will be two ATOMS of oxygen in one molecule on SnO2.

    How many atoms per mole?
     
  6. Jul 10, 2009 #5
    6.022x1023 per mole yes?, my problem is figuring out how many mols of O are in 1 molecule of SnO2.

    So I must be wrong there with Avogadros number then?
     
  7. Jul 10, 2009 #6

    Borek

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    Yes.
     
  8. Jul 10, 2009 #7
    I figured it out. Pretty easy. There is 2 atoms of O in the molecule. Therefore there is 2 x 4.5 x 1020 atoms in 4.5 x 1020 molecules... simple.

    Then convert atoms into moles by dividing by avogadros #.

    thanks.
     
  9. Jul 11, 2009 #8

    symbolipoint

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    Finally, Yes.
     
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