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Homework Help: Calculate the number of molecules of O2 when given the number of moles

  1. Dec 16, 2017 #1
    1. The problem statement, all variables and given/known data
    After balancing an equation, there are 1.82 moles of O2.

    Calculate the number of molecules of O2. given moles.
    2. Relevant equations


    3. The attempt at a solution
    in every O2 molecule, there are 2 moles of O.
    so if the number of moles of O2 molecule is 1.82. then 1.82*2= 3.65 moles.

    number of molecules= 3.65*6.022*10^23= 2.19*10^24.
    Correct?
     
  2. jcsd
  3. Dec 16, 2017 #2

    mfb

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    Staff: Mentor

    In every single molecule?
    That is the number of oxygen atoms. The question asked about the number of O2 molecules.
     
  4. Dec 16, 2017 #3
    Oh.. so the number of molecules is just no. of moles times molar mass?
    no need to multiply by 2?
     
  5. Dec 16, 2017 #4

    Borek

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    Number of moles times molar mass is a sample mass.

    Think about a mole as of an overgrown dozen, with 6.02×1023 objects instead of 12. You have two dozens of molecules - how many molecules? You have two moles of molecules - how many molecules?
     
  6. Dec 16, 2017 #5
    2*6.02×1023

    the question included no of moles
     
  7. Dec 16, 2017 #6

    mfb

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    Right.
     
  8. Dec 17, 2017 #7

    epenguin

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    Maybe you have go the question confused with the other possible similar kind of questions.
    Forget everything you know about oxygen - it's irrelevant here.
    Calculate the number of molecules of anything in 1.82 moles of that thing.
    Is the same for anything.
     
  9. Dec 17, 2017 #8

    Borek

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    Beware: part of the OP answer was plainly wrong.
     
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