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Homework Help: Chemistry Mole calculations

  1. Sep 17, 2010 #1
    1. The problem statement, all variables and given/known data

    Determine the number of moles of Nitrogen atoms in a sample of C7H5(NO2)3 that has the same number of oxygen atoms as 12.6 grams of sugar.


    2. Relevant equations
    Mole calculations


    3. The attempt at a solution

    First find the amount of moles of Oxygen in sugar. Multiply 12.6g by 96grams O/ 180grams sugar to get 6.72grams of sugar. The divide 6.72grams by 16 to get 0.42 moles of Oxygen. Then I'm struggling at the next part. To get the same amount of moles of Nitrogen shouldn't I just divide 0.42 by 3 to get 0.14? 0.14 was not the correct response on mastering chem.
     
  2. jcsd
  3. Sep 17, 2010 #2
    Determine the number of moles of Nitrogen atoms in a sample of C7H5(NO2)3 that has the same number of oxygen atoms as 12.6 grams of sugar.


    First calculate the no. of oxygen atoms in sugar
    moles of sugar = 12.6/342
    no. of O atoms= 12.6/342 x 11x N where N is avogadro number


    Let the mass of the compound given be m
    moles of this compound= m/227
    no of O atoms= 6 x m/227 x N

    equate and get m,
    I got it as 15.3 g
    Now moles of nitrogen atoms = 15.3/227 x 3
     
  4. Sep 17, 2010 #3
    Isn't the molar mass of sugar 180 g/mole not 342?
     
  5. Sep 17, 2010 #4

    Borek

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    Staff: Mentor

    What sugar? Ribose? Arabinose? Xylose? Gulose? Lyxose? Psicose? Fructose? Sorbose? Tagatose? Allose? Altrose? Glucose? Mannose? Idose? Galactose? Talose? Sucrose? Lactose? Maltose? Trehalose? Turanose? Cellobiose? Ribulose?
     
  6. Sep 17, 2010 #5
    My bad, I meant glucose. Thanks for showing the steps to solving the problem.
     
  7. Sep 17, 2010 #6
    Here in this question 'sugar' can be assumed as sucrose as nothing is mentioned about it.
     
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