Class 12th

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Rubber is a natural polymer. It is also known as an elastomer due to its elastic properties. It is manufactured from rubber latex.

This is a short answer type question as classified in NCERT Exemplar

The cis-polyisoprene molecule is made up of several chains that are held together by weak van there Waals interactions and has a coiled structure. Thus, it can be stretched like a spring and exhibits elastic properties.

This is a short answer type question as classified in NCERT Exemplar

The polymer shown above is cross-linked or network polymer. They are formed from bi or tri-functional monomers that contain strong covalent bond between polymer chains.

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This is a type of chain-growth polymerization. The molecules of the same monomer or different monomer are added together to form this type of polymer.

This is a short answer type question as classified in NCERT Exemplar

Addition polymers formed by the polymerization from two different monomers are co-polymers. The above-given polymer is a co-polymer. For example Buna-N, Buna-S.

This is a short answer type question as classified in NCERT Exemplar

Addition polymers formed by the polymerization of a single monomeric species are known as homopolymers. The above-given polymer is a homopolymer.

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While manufacturing tyre rubber, 5 % sulfur is used as a crosslinking agent. A natural linear polymer of 2-methyl-1, 3-butadiene becomes hard on treatment with sulfur and forms vulcanised rubber. The structure of the product formed is,

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Option (A) and (D)

Explanation: Vulcanisation is a process used to improve the physical properties of natural rubber. This method involves heating a mixture of raw rubber, sulphur, and an appropriate additive to temperatures ranging from 373 K to 415 K. Sulphur forms cross links at the reactive sites of double bonds during vulcanisation, stiffening the rubber.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A), (B) and (D)

Explanation: Polyacrylonitrile is formed by the addition polymerisation of acrylonitrile in the presence of a peroxide catalyst. Polyacrylonitrile is used as a wool substitute in the manufacture of commercial fibers such as orlon or acrilan.

Polystyrene has the monomer unit styrene.

Teflon is made by heating tetrafluoroethene at high pressures with a free radical or persulphate catalyst.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A) and (D)

Explanation: Polyamides: These polymers with amide linkages are important examples of synthetic fibers and are known as nylons.

Polyesters: These are the polycondensation products of dicarboxylic acids and diols.

Dacron or terylene is the most well-known example of a polyester.