Chemistry Materials Question - Weight % Fraction

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To determine the fraction of the ethylene mer in a copolymer consisting of 62 wt% ethylene and 38 wt% propylene, the calculation involves finding the weight contributions of each component. The weight of ethylene is calculated as 17.39 and propylene as 15.98. The fraction of ethylene is then found by dividing the weight of ethylene by the total weight of both components, resulting in a fraction of 0.521. This method parallels the approach used in determining empirical formulas from elemental analysis. The final answer should be expressed with three decimal points.
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Heres a question I am 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!
 
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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 C_xH_yO_z.

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