If N₁, N₂, N₃,.... are the number of molecules with molecular masses M₁, M₂, M₃..... respectively, then mass average molecular mass is expressed.

1. $\frac{{\mathrm{\Sigma N}}_{\mathrm{i}}{\mathrm{M}}_{\mathrm{i}}^2}{{\mathrm{\Sigma N}}_{\mathrm{i}}{\mathrm{M}}_{\mathrm{i}}}$

2. $\frac{{\mathrm{\Sigma N}}_{\mathrm{i}}{\mathrm{M}}_{\mathrm{i}}}{{\mathrm{\Sigma N}}_{\mathrm{i}}}$

3. $\frac{{\mathrm{\Sigma M}}_{\mathrm{i}}^2}{{\mathrm{\Sigma N}}_{\mathrm{i}}}$

4. $\frac{{\mathrm{\Sigma N}}_{\mathrm{i}}{\mathrm{M}}_{\mathrm{i}}}{{\mathrm{\Sigma M}}_{\mathrm{i}}}$

 

A copolymer of vinyl chloride and vinyl acetate is called:

1. Vinylon

2. Saran

3. Dynel

4. Orlon

In vulcanisation of rubber:

(1) Sulphur reacts to form new compound.

(2) Sulphur cross-links are introduced which resists wear and tear due to friction.

(3) Sulphur forms a very thin protective layer over rubber.

(4) All of the above.

The starting materials of PCTFE are:

(1) monochloro trifluoro ethylene

(2) tetrafluoroethylene

(3) vinyl chloride

(4) styrene

The abbreviation PDI refers to:

(1) name of the polymer

(2) polydispersity index of polymer

(3) application of polymer

(4) poly diagonal index

Caprolactam can be obtained from:

(1) benzaldehyde

(2) cyclohexane

(3) benzophenone

(4) adipic acid

The monomer units of silicons a water repellant, acid resistant and heat resistant polymer is:

1. Si                         

2. SiO₂

3. R₂SiO                   

4. None of these

A polymer of acrylonitrile is called:

1. Saran

2. Orlon

3. Dacron

4. Tetron

Which one of the following pairs is not correctly matched?

1. Terylene—condensation polymer of terephthalic acid and ethylene glycol

2. Teflon—thermally stable cross-linked polymer of phenol and formaldehyde

3. Perspex—a homopolymer of methyl methacrylate

4. Synthetic rubber —a copolymer of butadiene and styrene

Natural silk and artificial silk differ in one respect that one of them contains:

(1) N                     

(2) S

(3) P                       

(4) none of these