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NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET PDF Download

MULTIPLE CHOICE QUESTIONS - I

Q.1. Which of the following polymers of glucose is stored by animals?
(1) Cellulose
(2) Amylose
(3) Amylopectin
(4) Glycogen
Ans. 
(4)
Solution.

Glycogen is a polymer of glucose found in liver, brain and muscles of animals. Cellulose is a polymer found in plant while amylase and amylopectin are structural units of starch.

Q.2. Which of the following is not a semisynthetic polymer?
(1) Cis-polyisoprene
(2) Cellulose nitrate
(3) Cellulose acetate
(4) Vulcanised rubber
Ans. 
(1)
Solution.

m-polyisoprene is a natural polymer.

Q.3. The commercial name of polyacrylonitrile is _________.
(1) Dacron
(2) Orlon (acrilan)
(3) PVC
(4) Bakelite
Ans. 
(2)
Solution.

The commercial name of polyacrylonitrile is Orion or acrilan.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

Q.4. Which of the following polymer is biodegradable?
(1)NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
(2) NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
(3) NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
(4) NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
Ans. 
(3)
Solution.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

Q.5. In which of the following polymers ethylene glycol is one of the monomer units?
(1)NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
(2)NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
(3)NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
(4)NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
Ans. (a)
Solution.
Given polymer can be obtained condensation polymerization of ethylene glycol and phthalic acid with the elimination of water molecule.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
Q.6. Which of the following statements is not true about low density polythene?
(1) Tough
(2) Hard
(3) Poor conductor of electricity
(4) Highly branched structure
Ans. 
(2)
Solution.

Low density polythene is tough but flexible (not too hard) and a poor conductor of electricity. It has highly branched structure.

Q.7.NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEETis a polymer having monomer units _________.
(1)NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
(2)NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
(3)NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
(4)NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

Ans. (1)
Solution.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

Q.8. Which of the following polymer can be formed by using the following monomer unit?
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET(1) Nylon 6, 6
(2) Nylon 2–nylon 6
(3) Melamine polymer
(4) Nylon-6

Ans. (4)
Solution.
Nylon -6 is the polymer formed by polymerisation of caprolactam.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEETNCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET


MULTIPLE CHOICE QUESTIONS - II

Note : In the following questions two or more options may be correct.
Q.9. Which of the following polymers, need at least one diene monomer for their preparation?
(1) Dacron
(2) Buna-S

(3) Neoprene
(4) Novolac
Ans. 
(2, 3)
Solution.

Buna-S and neoprene are two such polymers which need at least one diene monomer for their preparation.
(b) Buna-S is prepared by copolymerization of 1, 3-butadierie and styrene.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET(c) Neoprene is prepared by polymerisation of chloroprene
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
Q.10. Which of the folloiwng are characteristics of thermosetting polymers?
(1) Heavily branched cross linked polymers.
(2) Linear slightly branched long chain molecules.
(3) Become infusible on moulding so cannot be reused.
(4) Soften on heating and harden on cooling, can be reused.
Ans. 
(1, 3)
Solution.

Thermosetting polymers are heavily branched cross linked polymers. They cannot be reused because they cannot melt on heating and cannot be remoulded.

Q.11. Which of the following polymers are thermoplastic?
(1) Teflon
(2) Natural rubber
(3) Neoprene
(4) Polystyrene
Ans. 
(1, 4)
Solution.

Teflon and polystyrene are thermoplastics since they can be moulded again by heating and melting.

Q.12. Which of the following polymers are used as fibre?
(1) Polytetrafluoroethane
(2) Poly chloroprene
(3) Nylon
(4) Terylene
Ans. 
(3, 4)
Solution.

Nylon and terylene are used as fibres due to strong intermolecular forces like H-bonding which lead to close packing in chain and thus impart crystalline nature.

Q.13. Which of the following are addition polymers?
(1) Nylon
(2) Melamine formaldehyde resin
(3) Orlon
(4) Polystyrene
Ans. 
(3, 4)
Solution.

Orion and polystyrene are addition polymers made by polymerisation of CH2 = CH – CN (acrylonitrile) and, C6H5 – CH = CH2 styrene respectively.

Q.14. Which of the following polymers are condensation polymers?
(1) Bakelite
(2) Teflon
(3) Butyl rubber
(4) Melamine formaldehyde resin
Ans. 
(1, 4)
Solution.

Bakelite is a condensation polymer of phenol and formaldehyde. Melamine formaldehyde resin is a condensation polymer of melamine (2, 4, 6-triamino-1, 3, 5-triazine) and formaldehyde.

Q.15. Which of the following monomers form biodegradable polymers?
(1) 3-hydroxybutanoic acid + 3-hydroxypentanoic acid
(2) Glycine + amino caproic acid
(3) Ethylene glycol + phthalic acid
(4) Caprolactum
Ans. 
(1, 2)
Solution.
The polymers which are easily decomposed and not harmful for the environment are known as biodegradable polymer.
(1) PHBV is obtained by condensation polymerization of 3 hydroxybutanoic acid and 3 hxydroypentanoic acid.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET(2) Glycine and aminocaproic acid produces nylon-2-nylon-6 polymer.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
Q.16. Which of the following are example of synthetic rubber?
(1) Polychloroprene
(2) Polyacrylonitrile
(3) Buna-N
(4) cis-polyisoprene
Ans. 
(1, 3)
Solution.

Polychloroprene is a polymer of chloroprene and it is synthethic rubber
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEETBuna-N is a synthetic rubber made from the polymerisation of 1, 3-butadiene and acrylonitrile
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
Q.17. Which of the following polymers can have strong intermolecular forces?
(1) Nylon
(2) Polystyrene
(3) Rubber
(4) Polyesters
Ans. 
(1, 4)
Solution.

Nylon and polyester are thread forming fibres which possesses high tensile strength and high melting point. They have strong intermolecular forces like hydrogen bonding.

Q.18. Which of the following polymers have vinylic monomer units?
(1) Acrilan
(2) Polystyrene
(3) Nylon
(4) Teflon
Ans. 
(1, 2, 4)
Solution.

Acrilan, polystyrene and teflon has vinylic monomer units shown as follows:
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEETNCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEETNCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
Q.19. Vulcanisation makes  rubber __________.
(1) More elastic
(2) Soluble in inorganic solvent
(3) Crystalline
(4) More stiff
Ans. 
(1, 4)
Solution.

Vulcanisation makes rubber more elastic and more stiff. On vulcanization sulphur forms cross links at the reactive sites of double bonds or at their reactive allylic position and thus rubber gets stiffened.


SHORT ANSWER TYPE QUESTIONS

Q.20. A natural linear polymer of 2-methyl-1, 3-butadiene becomes hard on treatment with sulphur between 373  to 415 K and —S—S— bonds are formed between chains. Write the structure of the product of this treatment?
Ans.
Vulcanized rubber.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
When it is heated with s at 373 - 415 K, it results into -S-S- links forming.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

Q.21. Identify the type of polymer. —A—A—A—A—A—A—
Ans.
It is a homopolymer, since its repeating structural unit is derived from only one type of monomer units, i.e., A.

Q.22. Identify the type of polymer. —A—B—B—A—A—A—B—A—
Ans.
It is a copolymer, since, its repeating structural unit is derived from two types of monomer units, i.e., A and B.

Q.23. Out of chain growth polymerisation and step growth polymerisation, in which type will you place the following.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
Ans. 
It is an example of chain growth polymerisation, since in this polymerisation only addition occurs.

Q.24. Identify the type of polymer given in the following figure.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
Ans. It is a cross linked polymer, since the various polymer chains are joined together to form a three-dimensional network structure (giant molecule).

Q.25. Identify the polymer given below :
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
Ans. The polymer is cis-polyisoprene (natural rubber), since the polymer is formed by 1, 4-addition of 2-methyl buta-1, 3-diene (isoprene).

Q.26. Why are rubbers called elastomers?
Ans.
Rubbers are stretched on application of force and come to its original position after the force is removed. Therefore, these are called elastomers.

Q.27. Can enzyme be called a polymer?
Ans.
Enzymes are biocatalysts which are proteins and thus can be called polymers.

Q.28. Can nucleic acids, proteins and starch be considered as step growth polymers?
Ans. 
Yes, step growth polymers (nucleic acids, proteins and starch) are conden-sation polymers and they can be formed by the loss of simple molecule like water leading to the formation of high molecular mass polymers.

Q.29. How is the following resin intermediate prepared and which polymer is formed by this monomer unit?
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEETAns. Melamine and formaldehyde are starting materials for this intermediate. Its polymerisation gives melamine formaldehyde polymer.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

Q.30. To have practical applications why are cross links required in rubber?
Ans. 
The cross links make the rubber hard, tough with greater tensile strength. The vulcanized rubber has excellent elasticity, low water absorption tendency, resistance to oxidation arid organic solvents.

Q.31. Why does cis-polyisoprene possess elastic property?
Ans. 
The cw-polyisoprene molecule consists of various chains held together by weal van der Waals interactions and has a coiled structure. Thus, it can be stretched like a spring and shows elastic properties.

Q.32. What is the structural difference between HDP and LDP? How does the structure account for different behaviour and nature, hence the use of a polymer?
Ans. 
LDP consists of highly branched chain molecules. Due to branching, the molecules do not pack well and therefore, it has low density (0.92 g cm 3) and low melting point. LDP is transparent of moderate tensile strength and high toughness. It is chemically inert. HDP consists of linear chains and therefore, the molecules can closely pack in space. Therefore, it has high density (0.97 g cm 3) and high melting point. It is quite hard, tougher and has greater tensile strength than LDP.

Q.33. What is the role of benzoyl peroxide in addition polymerisation of alkenes? Explain its mode of action with the help of an example.
Ans. 
Benzoyl peroxide acts as an initiator in free radical addition polymerisation of alkenes by providing chain initiation. The radical formed adds to the carbon-carbon double bond of an alkene molecules and ultimately forms the polymer. The new free radical adds to a double bond of monomer to form a larger free radical which adds to another alkene molecules and ultimately forms the polymer.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
The radical formed adds to the carbon-carbon double bond of an alkene molecules and ultimately forms the polymer.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
The new free radical adds to a double bond of monomer to form a larger free radical which adds to another alkene molecules and ultimately forms the polymer.
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

Q.34. Which factor imparts crystalline nature to a polymer like nylon?
Ans. 
Strong intermolecular forces like hydrogen bonding and linear structure lead to close packing of polymer chains that imparts crystalline character.

Q.35. Name the polymers used in laminated sheets and give the name of monomeric units involved in its formation.
Ans. 
The polymer is urea-formaldehyde resin
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

Q.36. Which type of biomolecules have some structural similarity with synthetic polyamides? What is this similarity?
Ans. 
Proteins have structural similarity with synthetic polyamides. Polyamides and proteins both contain amide linkage.

Q.37. Why should the monomers used in addition polymerisation through free radical pathway be very pure?
Ans. 
Pure monomers are required because even the traces of impurities may act as initiators which leads to the formation of polymers of small chain lengths.


MATCHING TYPE QUESTIONS

Note : Match the items of Column I with the items in Column II.
Q.38. Match the polymer of column I with correct monomer of column II.

 Column I
 Column II
 (i) High density polythene (a) Isoprene
 (ii) Neoprene (b) Tetrafluoroethene
 (iii) Natural rubber (c) Chloroprene
 (iv) Teflon (d) Acrylonitrile
 (v) Acrilan (e) Ethene

Ans. (i → e), (ii → c), (iii → a), (iv → b), (v → d)

Q.39. Match the polymers given in Column I with their chemical names given in Column II.

 Column I Column II
 (i) Nylon 6 (a) Polyvinyl chloride
 (ii) PVC (b) Polyacrylonitrile
 (iii) Acrilan (c) Polycaprolactum
 (iv) Natural rubber (d) Low density polythene
 (v) LDP (e) cis-polyisoprene

Ans. (i → c), (ii → a), (iii → b), (iv → e), (v → d)

Q.40. Match the polymers given in Column I with their commercial names given in Column II.

 Column I Column II
 (i) Polyester of glycol and phthalic acid (a) Novolac
 (ii) Copolymer of 1, 3-butadiene and styrene (b) Glyptal
 (iii) Phenol and formaldehyde resin (c) Buna-S
 (iv) Polyester of glycol and terephthalic acid (d) Buna-N
 (v) Copolymer of 1, 3-butadiene and acrylonitrile (e) Dacron

Ans.(i → b), (ii → c), (iii → a), (iv → e), (v → d)

Q.41. Match the polymers given in Column I with their main applications given in Column II.

 Column I Column II
 (i) Bakelite (a) Unbreakable crockery
 (ii) Low density polythene (b) Non-stick cookwares
 (iii) Melamine-formaldehyde resin (c) Packaging material for shock absorbance
 (iv) Nylon 6 (d) Electrical switches
 (v) Polytetrafluoroethane (e) Squeeze bottles
 (vi) Polystyrene (f) Tyre, cords

Ans. (i → d), (ii → e), (iii → a), (iv → f), (v → b), (vi → c)

Q.42. Match the polymers given in Column I with the preferred mode of polymerisation followed by their monomers.

 Column I Column II
 (i) Nylon-6,6 (a) Free radical polymerisation
 (ii) PVC (b) Ziegler -Natta polymerisation or coordination polymerisation
 (iii) HDP (c) Anionic polymerisation

 (d) Condensation polymerisation

Ans. (i → d), (ii → a), (iii → b)

Q.43. Match the polymers given in Column I with the type of linkage present in them given in Column II.

 Column I Column II  
 (i) Terylene (a) Glycosidic linkage
 (ii) Nylon (b) Ester linkage
 (iii) Cellulose (c) Phosphodiester linkage
 (iv) Protein (d) Amide linkage
 (v) RNA

Ans. (i → b), (ii → d), (iii → a), (iv → d), (v → c)

Q.44. Match materials given in Column I with the polymers given in Column II.

 Column I Column II
 (i) Natural rubber latex
 (a) Nylon
 (ii) Wood laminates (b) Neoprene
 (iii) Ropes and fibres (c) Dacron
 (iv) Polyester fabric (d) Melamine formaldehyde resins
 (v) Synthetic rubber (e) Urea-formaldehyde resins
 (vi) Unbreakable crockery (f) cis-polyisoprene

Ans. (i → f), (ii → e), (iii → a), (iv → c), (v → b), (vi → d)

Q.45. Match the polymers given in Column I with their repeating units given in Column II.

 Column I Column II
 (i) Acrilan (a) NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
 (ii) Polystyrene (b) NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
 (iii) Neoprene (c)NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
 (iv) Novolac (d)NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
 (v) Buna—N (e) NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

 (f)NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

Ans. (i → d), (ii → a), (iii → b),(iv → e),(v → c)


ASSERTION AND REASON TYPE

Note : In the following questions a statement of assertion followed by a statement of reason is given. 
Q.46. Assertion : Rayon is a semi synthetic polymer and is taken as a better choice than cotton fabric.
Reason : 
Mechanical and aesthetic properties of cellulose can be improved by acetylation.
(1) Assertion and reason both are correct statement but reason does not explain assertion.
(2) Assertion and reason both are correct statements and reason explains the assertion.
(3) Both assertion and reason are wrong statement.
(4) Assertion is correct statement and reason is wrong statement.
(5) Assertion is wrong statement and reason is correct statement.

Ans. (2)
Solution.
Rayon is semi-synthetic polymer and is a better choice than cotton because properties of cellulose are improved by acetylation while processing.

Q.47. Assertion : Most of the Synthetic polymers are not biodegradable.
Reason : 
Polymerisation process induces toxic character in organic molecules.
(1) Assertion and reason both are correct statement but reason does not explain assertion.
(2) Assertion and reason both are correct statements and reason explains the assertion.
(3) Both assertion and reason are wrong statement.
(4) Assertion is correct statement and reason is wrong statement.
(5) Assertion is wrong statement and reason is correct statement.
Ans. 
(4)
Solution.

Most of the synthetic polymers are not degraded by enzymatic hydrolytic and environmental oxidation. Polymerisation does not induce toxic characters.

Q.48. Assertion : Olefinic monomers undergo addition polymerisation.
Reason : 
Polymerisation of vinylchloride is initiated by peroxides/ persulphates.
(1) Assertion and reason both are correct statement but reason does not explain assertion.
(2) Assertion and reason both are correct statements and reason explains the assertion.
(3) Both assertion and reason are wrong statement.
(4) Assertion is correct statement and reason is wrong statement.
(5) Assertion is wrong statement and reason is correct statement.
Ans. 
(1)
Solution.

Olefins like ethene undergo addition polymerization to give polymer like polythene.

Q.49. Assertion : Polyamides are best used as fibres because of high tensile strength.
Reason : 
Strong intermolecular forces (like hydrogen bonding within polyamides) lead to close packing of chains and increase the crystalline character, hence, provide high tensile strength to polymers.
(1) Assertion and reason both are correct statement but reason does not explain assertion.
(2) Assertion and reason both are correct statements and reason explains the assertion.
(3) Both assertion and reason are wrong statement.
(4) Assertion is correct statement and reason is wrong statement.
(5) Assertion is wrong statement and reason is correct statement.
Ans. 
(2)
Solution.

Polyamides like nylons are best used fibres. They have high tensile strength due to presence of strong inter molecular hydrogen bond.

Q.50. Assertion : For making rubber synthetically, isoprene molecules are polymerised.
Reason : 
Neoprene (a polymer of chloroprene) is a synthetic rubber.
(1) Assertion and reason both are correct statement but reason does not explain assertion.
(2) Assertion and reason both are correct statements and reason explains the assertion.
(3) Both assertion and reason are wrong statement.
(4) Assertion is correct statement and reason is wrong statement.
(5) Assertion is wrong statement and reason is correct statement.
Ans. 
(5)
Solution.

Isoprene molecule is the monomer for natural rubber, while neoprene a synthetic rubber is formed by polymerisation of chloroprene.

Q.51. Assertion : Network polymers are thermosetting.
Reason : 
Network polymers have high molecular mass.
(1) Assertion and reason both are correct statement but reason does not explain assertion.
(2) Assertion and reason both are correct statements and reason explains the assertion.
(3) Both assertion and reason are wrong statement.
(4) Assertion is correct statement and reason is wrong statement.
(5) Assertion is wrong statement and reason is correct statement.
Ans. 
(1)
Solution.

Extensive cross linking during polymerisation leads to the formation of three-dimensional network which is hard, infusible and insoluble.

Q.52. Assertion : Polytetrafluoroethene is used in making non-stick cookwares.
Reason : 
Fluorine has highest electronegativity.
(1) Assertion and reason both are correct statement but reason does not explain assertion.
(2) Assertion and reason both are correct statements and reason explains the assertion.
(3) Both assertion and reason are wrong statement.
(4) Assertion is correct statement and reason is wrong statement.
(5) Assertion is wrong statement and reason is correct statement.
Ans. 
(1)
Solution.

Teflon is used in making nonstick cookware as it is chemically inert and thermally stable.


LONG ANSWER TYPE QUESTIONS

Q.53. Synthetic polymers do not degrade in the environment for a long time. How can biodegradable synthetic polymers be made. Differentiate between biopolymers and biodegradable polymers and give examples of each type.
Ans. 
Synthetic polymers are quite resistant to environmental degradation process and are responsible for accumulation of polymer solid waste material. New biodegradable synthetic polymers have been designed and developed. These polymers contain similar functional groups as present in biopolymers, e.g., aliphatic polyesters
Biopolymers are polymers of amino acids or carbohydrates which are linked to each other by peptide or glycosidic linkages as shown below
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
Polymer of amino acid Biopolymer can or cannot be biodegradable. e.g., protein, starch etc., are biodegradable but keratin are non-biodegradable. Biodegradable polymer are polymers which can be degradable always, e.g., DHBV nylon-2, nylon-6.

Q.54. Differentiate between rubbers and plastics on the basis of intermolecular forces.
Ans. 
Rubber is a natural polymer which is capable of returning to its original length, shape or size after being stretched or deformed. It is a common example of an elastomer. The m-polyisoprene molecule (natural rubber) consists of various chains held together by weak van der Waals interactions and has a coiled structure.
Thermoplastics are the polymers in which intermolecular forces of attraction are in between those of elastomers and fibres. They are neither very strong nor very weak and have no cross links between the chains molecules capable of repeatedly softening on heating and hardening on cooling.

Q.55. Phenol and formaldehyde undergo condensation to give a polymar (A) which on heating with formaldehyde gives a thermosetting polymer (B). Name the polymers. Write the reactions involved in the formation of (A). What is the structural difference between two polymers?
Ans. 
Polymer ‘A’ is Novalac and‘‘B’ is Bakelite. The reactions involved in the formation of these two polymers are given below:
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET
NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

Novalac on heating with HCHO undergo cross-linkage to form an infusible solid called Bakelite.
Novolac is linear chain polymer while Bakelite is cross linked polymer.

Q.56. Low density polythene and high density polythene, both are polymers of ethene but there is marked difference in their properties. Explain.
Ans. 
Low density and high density polythenes are obtained under different reaction conditions. LDP is obtained through free radical addition at high pressure (1000 to 2000 atm) and a temperature of 350 K to 570 K and is highly branched structure. LDP is chemically inert and tough but slightly flexible.
High density polythene or HDP is obtained by addition polymerisation of ethene in presence of hydrocarbon solvent at low pressure of hydrocarbon solvent at low pressure (6-7 atm) and a temperature of 333 K to 343 K in presence of Ziegler-Natta catalyst. Under these conditions the polymer is linear and has high density due to close packing. It is tougher, and harder than LDP.

Q.57. Which of the following polymers soften on heating and harden on cooling? What are the polymers with this property collectively called? What are the structural similarities between such polymers? Bakelite, urea-formaldehyde resin, polythene, polyvinyls, polystyrene.
Ans. 
Polythene, polyvinyl and polystyrene soften on heating and harden on cooling. Such polymers are called thermoplastic polymers. These possess intermolecular forces of attraction whose strength lies between strength of intermolecular forces of elastomers and fibres. These polymers are linear or slightly branched long chain molecules.

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FAQs on NCERT Exemplar: Polymers (Old NCERT) - Chemistry Class 12 - NEET

1. What are polymers and how are they formed?
Ans. Polymers are large molecules made up of repeating subunits called monomers. They are formed through a process called polymerization, where monomers join together to form long chains or networks.
2. What are some common examples of polymers in everyday life?
Ans. Some common examples of polymers in everyday life include plastics, rubber, nylon, polyester, and DNA. These polymers are used in various applications such as packaging, clothing, construction materials, and biomedical devices.
3. How are polymers classified based on their structure?
Ans. Polymers can be classified into three main categories based on their structure: linear polymers, branched polymers, and cross-linked polymers. In linear polymers, the monomers are arranged in a straight chain. In branched polymers, side chains or branches are present along the main chain. Cross-linked polymers have covalent bonds between different polymer chains, forming a network structure.
4. What are the properties of polymers that make them useful in various applications?
Ans. Polymers possess several properties that make them useful in various applications. Some of these properties include high strength-to-weight ratio, flexibility, electrical insulation, chemical resistance, and low cost. These properties can be tailored by modifying the monomers and the polymerization process, leading to a wide range of polymer materials with different properties.
5. How are polymers recycled and what are the challenges associated with polymer recycling?
Ans. Polymers can be recycled through various processes such as mechanical recycling, chemical recycling, and energy recovery. Mechanical recycling involves melting and reprocessing the polymer to obtain new products. Chemical recycling involves breaking down the polymer into its monomers or small molecules for further processing. However, there are challenges associated with polymer recycling, such as the need for specialized recycling facilities, sorting and separation of different types of polymers, and the presence of additives or contaminants in the recycled material. These challenges need to be addressed to improve the efficiency and sustainability of polymer recycling.
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Important questions

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NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

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Previous Year Questions with Solutions

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NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

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NCERT Exemplar: Polymers (Old NCERT) | Chemistry Class 12 - NEET

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Summary

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Semester Notes

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past year papers

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Sample Paper

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