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?

Question

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? (A) 27,000 (B) 36,000 (C) 43,000 (D) 64,000

Tardigrade Admin · Accepted Answer

The number average molecular mass of the polymer: M =( Sigma M i N i / Sigma N i ) =(30(20000)+40(30000)+30(60000)/30+40+30) =36000

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?

27,000

36,000

43,000

64,000

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

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?