Answer:
Option C
Explanation:
$\because$ Number average molecular mass $(M\overline{n})$
=$\frac{N_{1} M_{1}+N_{2} M_{2}+N_{3} M_{3}}{N_{1}+ N_{2}+N_{3}}$
where, $N_{1},N_{2} $ and $N_{3}$ are number of molecules and $M_{1} , M_{2} $ and $M_{3}$ are respectively their molecular masses.
Given
$N_{1}$ = 50 and $M_{1}$ = 5000
$N_{2}$ = 100 and $M_{2}$ = 10000
$N_{3}$ = 50 and $M_{3}$ = 15000
Thus,
$M\overline{n}=\frac{N_{1} M_{1}+N_{2} M_{2}+N_{3} M_{3}}{N_{1}+ N_{2}+N_{3}}$
=$M\overline{n}=\frac{(50 \times 5000) +(100\times 10000)+(50\times 15000)}{50+ 100+50}$
= $\frac{(25,0000) +(1000000)+(750000)}{200}$
$M\overline{n}$=10,000
Hence, option (c) is the correct answer
