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  4. A sample of polymer contains 30 % molecules with molecular mass 20,000,40 % with molecular mass 30,000 and 30 % with molecular mass 60,000. What is the number average molecular mass of the polymer?

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Q. A sample of polymer contains $30 \%$ molecules with molecular mass $20,000,40 \%$ with molecular mass $30,000$ and $30 \%$ with molecular mass $60,000$. What is the number average molecular mass of the polymer?

ManipalManipal 2015

Solution:

The number average molecular mass of the polymer:
$M =\frac{\Sigma M _{ i } N _{ i }}{\Sigma N _{ i }}$
$=\frac{30(20000)+40(30000)+30(60000)}{30+40+30}$
$=36000$