Bihar Board Class 12 Chemistry Solutions Chapter 15 Polymers
BSEB Bihar Board Class 12 Chemistry Solutions Chapter 15 Polymers
Bihar Board Class 12 Chemistry Polymers Intext Questions and Answers
Question 1.
What are polymers?
Answer:
Polymers are high molecular mass substances consisting of large number of repeating structural units. They are also called as macromolecules. Some examples of polyethene, bakelite, rubber, nylon 6,6 etc.
Question 2.
How are polymers classified on the basis of structure?
Answer:
On the basis of structure, the polymers are classified as below :
- Linear polymer as polyethene, polyvinyl chloride etc.
- Branched-chain polymers as low-density polyethene.
- Cross-linked polymers such as bakelite, melamine etc.
Question 3.
Write the names of the monomers of the following polymers:
Answer:
(i) Hexamethylene diamine and adipic acid.
(ii) Caprolactum.
(iii) Tetrafluoroethene.
Question 4.
Classify the following as addition and condensation polymers:
Terylene, Bakelite, Polyvinylchloride, Polyethene.
Answer:
Addition polymers: Polyvinyl chloride, Polyethene. Condensation Polymers: Terylene, Bakelite.
Question 5.
Explain the difference between Buna-N and Buna-S.
Answer:
Buna-N is a copolymer of 1, 3-butadiene and acrylonitrile, whereas Buna-S is a copolymer of 1, 3-butadiene and styrene.
Question 6.
Arrange the following polymers in increasing order of their intermolecular forces.
(i) Nylon 6,6, Buna-S, Polyethene
(ii) Nylon 6, Neoprene, Polyvinylchloride.
Answer:
Polymers in increasing order of intermolecular forces
(i) Buna-S, Polyethene, Nylon 6,6.
(ii) Neoprene, Polyvinylchloride, Nylon 6.
Bihar Board Class 12 Chemistry Polymers Text Book Questions and Answers
Question 1.
Explain the terms polymer and monomers.
Answer:
(i) Polymer is a high molecular mass macromolecule consisting of repeating structural units derived from monomers, e.g., polyethene, polyvinyl chloride, Nylon 6,6 etc.
(ii) Monomer is a simple molecule capable of undergoing polymerization and leading to the formation of the corresponding polymer, e.g., ethene, vinyl chloride etc.
Question 2.
What are natural and synthetic polymers? Give two examples of each type.
Answer:
- Natural polymers are high molecular mass macromolecules and are found in plants and animals. The examples are proteins and nucleic acids.
- Synthetic polymers-They are man-made high molecular mass macromolecules. These include synthetic plastics, fibres and synthetic rubber. The two specific examples are polyethene and dacron.
Question 3.
Distinguish between the terms homopolymer and copolymer and give an example of each.
Answer:
(i) Addition polymers formed by the polymerisation of a single monomeric species are known as homopolymers e.g., polyethene.
(ii) Copolymers-These are the polymers made by the addition polymerization from two different monomers, e.g., Buna-S.
Question 4.
How do you explain the functionality of a monomers?
Answer:
Functionality-It is defined as the number of bonding sites in a monomer.
Question 5.
Define the term polymerization.
Answer:
Polymerization is a process of formation of a high molecular mass polymer from one or more monomers by linking together of repeating structural units with covalent bonds.
Question 6.
Is (NH-CHR-CO)n homopolymer or Copolymer?
Answer:
Since the unit (NH-CHR-CO)n is obtained from the single monomer unit NH2-CHR-COOH, it is a homopolymer.
Question 7.
In which classes, the polymers are classified on the basis of molecular forces?
Answer:
On the basis of molecular forces present between the chains of various polymers, the classification of polymers is given as follows :
- Elastomers,
- Fibres,
- Thermoplastics and
- Thermosetting plastics.
Question 8.
How can you differentiate between addition and condensation polymerization?
Answer:
In addition polymerization, the molecules of the same or different monomers add together to form a large polymer molecule without the elimination of simple molecules like H2O, HCl etc. Condensation polymerisation is a process in which two or more bifunctional molecules undergo a series of condensation reactions with the elimination of some simple molecules like H2O, HCl, alcohol and leading to the formation of polymers.
Question 9.
Explain the term copolymerization and give two examples.
Answer:
Copolymerization is a process in which a mixture of more than one monomeric species is allowed to polymerise. The copolymer contains multiple units of each monomer in the chain. The examples are copolymers of 1, 3-butadiene and styrene. Another example is the copolymer of 1,3-butadiene and acrylonitrile.
Question 10.
Write the free-radical mechanism for the polymerization of ethene.
Answer:
Ethene undergoes polymerization in the presence of benzoyl proxide through free radical mechanism as described below:
(i) Chain initiating step-
Question 11.
Define thermoplastics and thermosetting polymers with two examples of each.
Answer:
Thermoplastic polymer-It can be repeatedly softened on heating and hardened on cooling, hence it can be used again and again. The examples are polyethene and polypropylene etc.
Thermosetting Polymer-A thermosetting polymer is a permanent setting polymer as it gets hardened and set during moulding process and cannot be softened again. The examples are bakelite and melamine-formaldehyde polymers.
Question 12.
Write the monomers used for getting the following polymers, (i) Polyvinyl chloride, (ii) Teflon, (iii) Bakelite.
Answer:
- The monomer of polyvinyl chloride is vinyl chloride: CH2 = CHCl
- The monomer of Teflon is tetrafluoroethylene (CF2 = CF2).
- The monomers for the formation of bakelite are phenol (C6H5OH) and formaldehyde (HCHO).
Question 13.
Write the name and structure of one of the common initiators used in free radical addition polymerization.
Answer:
Question 14.
How do double bonds in rubber molecules influence their structure a.nd reactivity?
Answer:
From the structural point of view, the natural rubber is a linear cis-1, 4-polyisoprene. In the polymer double bonds are located between C2 and C3 of isoprene units. This cis-configuration about double bonds do not allow the chains to come closer for effective attraction due to weak intermolecular attractions. Hence the natural rubber has a coiled and shows elasticity.
Question 15.
Discuss the main purpose of vulcanisation of rubber.
Answer:
Natural rubber becomes soft at high temperature and brittle at low temperatures. On vulcanisation, sulphur forms cross-links at the reactive sites of double bonds and thus the rubber gets stiffened.
Question 16.
What are the monomeric repeating units of Nylon-6 and Nylon-6,6?
Answer:
The monomeric repeat unit of Nylon-6 polymer is [NH- (CH2)5-CO].
The monomeric repeat unit of Nylon-6,6 polymer is derived from the two monomers: hexamethylene diamine and adipic acid.
[NH-(CH2)6-NH-CO-(CH2)4-CO].
The two monomers are NH2 (CH2)6NH2 and COOH (CH2)4 COOH.
Question 17.
Write the names and structures of the monomers of the following polymers:
(i) Buna-S
(ii) Buna-N
(iii) Dacron
(iv) Neoprene.
Answer:
The names and structures of monomers are
Answer:
The monomers forming the polymer are:
(i) Decanoic acid HOOC-(CH2)8-COOH and Hexamethylene diamine H2N (CH2)6NH2.
Question 20.
What is a biodegradable polymer? Give an example of a biodegradable aliphatic polyester?
Answer:
Biodegradable Polymer is one which disintegrates of its own in biological systems during a certain period of time by enzymatic hydrolysis and to some extent by oxidation. Such a polymer does not cause any environment pollution.
The most important class of biodegradable polymers are aliphatic polyesters. One such example Poly-β-Hydroxybutyrate-co-β-Hydroxy valerate [PHBV]. It is a copolymer of 3-hydroxybutyric acid and 3-hydroxy pentanoic acid.