NCERT Solutions for Class 12 Science Chemistry Chapter 6 – Polymers
Here are step-by-step explanations for NCERT Solutions for Class 12 Science Chemistry Chapter 6 on Polymers. These solutions are highly favored by Chemistry students for completing homework and exam preparation. All questions and answers from the NCERT Book of Class 12 Science Chemistry Chapter 6, Polymers, are available here for free use. Page No 428: Question 15.1: What are polymers? ANSWER: Polymers are high molecular mass macromolecules, which consist of repeating structural units derived from monomers. Polymers have a high molecular mass (103 − 107u). In a polymer, various monomer units are joined by strong covalent bonds. These polymers can be natural as well as synthetic. Polythene, rubber, and nylon 6, 6 are examples of polymers. Page No 428: Question 15.2: How are polymers classified on the basis of structure? ANSWER: Polymers are classified on the basis of structure as follows: 1. Linear polymers: These polymers are formed of long straight chains. They can be depicted as: For e.g., high density polythene (HDP), polyvinyl chloride, etc. 2. Branched chain polymers: These polymers are basically linear chain polymers with some branches. These polymers are represented as: For e.g., low density polythene (LDP), amylopectin, etc. 3. Cross-linked or Network polymers: These polymers have many cross-linking bonds that give rise to a network-like structure. These polymers contain bi-functional and tri-functional monomers and strong covalent bonds between various linear polymer chains. Examples of such polymers include bakelite and melmac. Page No 428: Question 15.3: Write the names of monomers of the following polymers: ANSWER: (i) Hexamethylenediamine and adipic acid (ii) (iii) Tetrafluoroethene Page No 428: Question 15.4: Classify the following as addition and condensation polymers: Terylene, Bakelite, Polyvinyl chloride, Polythene. ANSWER: Addition polymers: Polyvinyl chloride, polythene Condensation polymers: Terylene, bakelite Page No 435: Question 15.5: Explain the difference between Buna-N and Buna-S. ANSWER: Buna − N is a copolymer of 1, 3−butadiene and acrylonitrile. Buna − S is a copolymer of 1, 3−butadiene and styrene. Page No 435: Question 15.6: Arrange the following polymers in increasing order of their intermolecular forces. (i) Nylon 6, 6, Buna-S, Polythene. (ii) Nylon 6, Neoprene, Polyvinyl chloride. ANSWER: Different types of polymers have different intermolecular forces of attraction. Elastomers or rubbers have the weakest while fibres have the strongest intermolecular forces of attraction. Plastics have intermediate intermolecular forces of attraction. Hence, the increasing order of the intermolecular forces of the given polymers is as follows: (i) Buna − S < polythene < Nylon 6, 6 (ii) Neoprene < polyvinyl chloride < Nylon 6 Page No 437: Question 15.1: Explain the terms polymer and monomer. ANSWER: Polymers are high molecular mass macromolecules composed of repeating structural units derived from monomers. Polymers have a high molecular mass (103 − 107u). In a polymer, various monomer units are joined by strong covalent bonds. Polymers can be natural as well as synthetic. Polythene, rubber, and nylon 6, 6 are examples of polymers. Monomers are simple, reactive molecules that combine with each other in large numbers through covalent bonds to give rise to polymers. For example, ethene, propene, styrene, vinyl chloride. Page No 437: Question 15.2: What are natural and synthetic polymers? Give two examples of each type. ANSWER: Natural polymers are polymers that are found in nature. They are formed by plants and animals. Examples include protein, cellulose, starch, etc. Synthetic polymers are polymers made by human beings. Examples include plastic (polythene), synthetic fibres (nylon 6, 6), synthetic rubbers (Buna − S). Page No 437: Question 15.3: Distinguish between the terms homopolymer and copolymer and give an example of each. ANSWER: Homopolymer Copolymer The polymers that are formed by the polymerization of a single monomer are known as homopolymers. In other words, the repeating units of homopolymers are derived only from one monomer. For example, polythene is a homopolymer of ethene. The polymers whose repeating units are derived from two types of monomers are known as copolymers. For example, Buna−S is a copolymer of 1, 3-butadiene and styrene. Page No 437: Question 15.4: How do you explain the functionality of a monomer? ANSWER: The functionality of a monomer is the number of binding sites that is/are present in that monomer. For example, the functionality of monomers such as ethene and propene is one and that of 1, 3-butadiene and adipic acid is two. Page No 437: Question 15.5: Define the term polymerisation. ANSWER: Polymerization is the process of forming high molecular mass (103 − 107u) macromolecules, which consist of repeating structural units derived from monomers. In a polymer, various monomer units are joined by strong covalent bonds. Page No 437: Question 15.6: Is , a homopolymer or copolymer? ANSWER: is a homopolymer because it is obtained from a single monomer unit, NH2−CHR−COOH. Page No 437: Question 15.7: In which classes, the polymers are classified on the basis of molecular forces? ANSWER: On the basis of magnitude of intermolecular forces present in polymers, they are classified into the following groups: (i) Elastomers (ii) Fibres (iii) Thermoplastic polymers (iv) Thermosetting polymers Page No 437: Question 15.8: How can you differentiate between addition and condensation polymerisation? ANSWER: Addition polymerization is the process of repeated addition of monomers, possessing double or triple bonds to form polymers. For example, polythene is formed by addition polymerization of ethene. Condensation polymerization is the process of formation of polymers by repeated condensation reactions between two different bi-functional or tri-functional monomers. A small molecule such as water or hydrochloric acid is eliminated in each condensation. For example, nylon 6, 6 is formed by condensation polymerization of hexamethylenediamine and adipic acid. Page No 437: Question 15.9: Explain the term copolymerisation and give two examples. ANSWER: The process of forming polymers from two or more different monomeric units is called copolymerization. Multiple units of each monomer are present in a copolymer. The process of forming polymer Buna−S from 1, 3-butadiene and styrene is an example of copolymerization Nylon 6, 6 is also a copolymer formed by hexamethylenediamine and adipic acid. Page No 437: Question 15.10: Write the free radical mechanism for the polymerisation of ethene. ANSWER: Polymerization of ethene to polythene consists of heating or exposing to …
NCERT Solutions for Class 12 Science Chemistry Chapter 6 – Polymers Read More »