If ${\mathrm{N}}_1,{\mathrm{N}}_2,{\mathrm{N}}_3\dots {\mathrm{N}}_{\mathrm{i}}$ are the number of molecules with molecular masses ${\mathrm{M}}_1,{\mathrm{M}}_2,{\mathrm{M}}_3\dots {\mathrm{M}}_{\mathrm{i}}$ respectively, then the number average molecular mass $\left({\overline{\mathrm{M}}}_{\mathrm{n}}\right)$ is given by

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

2. $\frac{\sum N_i{M}_i}{\sum N_i}$

3. $\frac{\sum M_i^2}{\sum N_j}$

4. $\frac{\sum N_i{M}_i}{\sum M_i}$

Orlon has a unit of -

1. Glycol

2. Isoprene

3. Vinyl cyanide

4. Acrolein

The biodegradable polymer among the following is:

1. Cellulose

2. Nylon-6

3. Polythene

4. Polyvinylchloride

The substance used to harden the rubber for tire manufacture is

(1) ${\mathrm{CaC}}_2$

(2) wax

(3) carbon black

(4) 1, 3-butadiene

Terylene is not a : 

1. Synthetic fiber

2. Thermosetting plastic

3. Step-growth polymer

4. Condensation polymer

Perlon is also known as:

1. Nylon-6, 10

2. Nylon-4, 4

3. Nylon 6, 6, 6

4. Nylon-6

Cellulose is a condensation polymer of

1. $\mathrm{\alpha }$-galactose

2. $\mathrm{\alpha }$-glucose

3. $\mathrm{\beta }$-glucose 

4. $\mathrm{\beta }$-galactose

Toluene di-isocyanate is used to prepare

(1) polyamides

(2) polyurethanes

(3) polycarbonates

(4) polyesters

An example of elastomer among the following is: 

1. Dacron

2. Melamine

3. Vulcanized rubber

4. Polystyrene

A polymer of prop-2-ene nitrile is called

(1) Tetron

(2) Saran

(3) Orlon

(4) Dacron