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Percent (by mass) composition

  1. Sep 8, 2009 #1
    % (by mass) composition

    1. The problem statement, all variables and given/known data
    Dopamine, C8 H11 O2 N is a neutroransmitter. Determine the percent (by mass) composition of each of the elements in dopamite.


    2. Relevant equations



    3. The attempt at a solution
    8C atoms= 12 (12.0) = 44.0amu
    11H atoms = 11 (1.0) = 11.0 amu
    2O atoms = 2 (16.00) = 32.0 amu
    1N atoms = 1 (14.01) = 14.01 amu
    total: 101.01 amu

    %C (8)(12.0 amu)
    ______________ = 95.0%
    101.01
    %H (11)(1.0 amu)
    _____________ = 10.8%
    101.01

    %O (2)(16.00)
    _______________ = 31.6%
    101.01

    %N (1)(14.01)
    ___________ = 13.8%
    101.01



    please help/tell me if its correct or not.
     
    Last edited: Sep 8, 2009
  2. jcsd
  3. Sep 8, 2009 #2

    Borek

    User Avatar

    Staff: Mentor

    Re: % (by mass) composition

    8*12 is not 44.

    --
     
  4. May 18, 2011 #3
    Re: % (by mass) composition

    As it were, your calculations indicate a higher mass than is possible.

    C8 H11 O2 N

    MW = 8*12 + 11 + 2*16 + 14 = 96 + 11 + 32 + 14 = 153
     
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