Molecular Weight of Polymers

Q. If $N_1,N_2,N_3,......$ are the number of molecules with molecular masses $M_1,M_2,M_3,......$ respectively, the mass average molecular mass is expressed as?

1. $\frac{\sum N_i{M_i}^2}{\sum N_i{M}_i}$
2. $\frac{\sum N_i{M}_i}{\sum N_i}$
3. $\frac{\sum {M_i}^2}{\sum N_i}$
4. $\frac{\sum N_i{M}_i}{\sum M_i}$

Q. If $N_1,N_2,N_3,......$ are the number of molecules with molecular masses $M_1,M_2,M_3,......$ respectively, the mass average molecular mass is expressed as?

1. $\frac{\sum N_i{M_i}^2}{\sum N_i{M}_i}$
2. $\frac{\sum N_i{M}_i}{\sum N_i}$
3. $\frac{\sum {M_i}^2}{\sum N_i}$
4. $\frac{\sum N_i{M}_i}{\sum M_i}$

Q.

of a polymer containing 30% molecules with molecular mass 20, 000, 40% have 30, 000 and the rest have 60, 000 is

1. 36 x 10⁵

2. 36 x 10³

3. 18 x 10³

4. 18 x 10⁵

Q.

Number average molecular mass and weight average molecular mass of synthetic polymers are related as?

1. $M_w>1/2M_n$

2. $M_w=M_n$

3. $M_w>M_n$

4. $M_w<M_n$