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Chemistry Materials Question - Weight % Fraction

  1. Sep 24, 2007 #1
    Heres a question Im stuck with

    Crosslinked polymers consisting of 62 wt% ethylene and 38 wt% propylene may have elastic properties similar those for natural rubber. For a copolymer of this composition, determine the fraction of the ethylene mer.

    Express your answer with three decimal points.



    I honestly am lost with how to do this question...

    What I did was....

    Found the weight of ethylene (28.052) and the weight of propylene (42.078)...then multipled by the percentages and got...

    28.052*0.62 = 17.39
    42.078*0.38 = 15.98

    then..

    fraction = 17.39/(15.98+17.39)

    I doubt this is right...any help would be much appreciated.

    Thanks in advance!
     
  2. jcsd
  3. Sep 26, 2007 #2

    chemisttree

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    This problem is done the same way in which you have done similar problems using the results from an elemental analysis.

    ie. What is the empirical formula of a compound composed of carbon, hydrogen and oxygen given the following elemental analysis:

    C - 53.2%
    H -17.4%

    The answer would be given in the form of [tex]C_xH_yO_z[/tex].

    Do this the same way, substituting ethylene or propylene for one of the elements. The answer will be in the form [tex]CH_3-[CH_2-CH_2]_m-[CH_2(CH_3)CH_2]_n-CH_3.[/tex]
     
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