CBSE Class 12 Chemistry Chapter 15: Polymers NCERT Solutions

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NCERT Solutions PDF Class 12 PDF

This resource provides detailed NCERT Solutions for Class 12 Chemistry Chapter 15, focusing on Polymers. It covers key concepts such as natural and synthetic polymers, classification based on structure and source, and different polymerization techniques like addition and condensation polymerization. The solutions explain various types of polymers including biodegradable polymers, semisynthetic polymers, and common examples like glycogen, cellulose, polyacrylonitrile, and polyesters. This chapter is crucial for understanding the building blocks of materials around us and their formation processes. These solutions are designed to help students grasp complex topics, clarify doubts, and prepare effectively for their CBSE board examinations by offering step-by-step explanations and accurate answers to the chapter's exercises.

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Quick info

BoardCBSE
ClassClass 12
SubjectChemistry Exemplar
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 15

Chapter summary

Chapter 15 on Polymers in the Class 12 Chemistry syllabus covers the fundamental principles of polymer science. The NCERT Solutions provided here explain the classification of polymers based on their source (natural, semisynthetic, synthetic), structure (linear, branched, cross-linked), and mode of polymerization (addition, condensation). It delves into specific examples like biodegradable polymers and common synthetic polymers, offering clear explanations for each concept and question.

Learning outcomes

  • Identify polymers stored by animals.
  • Distinguish between natural, semisynthetic, and synthetic polymers.
  • Recognize commercial names of polymers like polyacrylonitrile.
  • Identify biodegradable polymers.
  • Determine monomers involved in the formation of specific polymers like Terylene.

Topics covered

Paper topics

  • Classification of Polymers
  • Natural Polymers
  • Semisynthetic Polymers
  • Synthetic Polymers
  • Addition Polymerization
  • Condensation Polymerization
  • Biodegradable Polymers
  • Glycogen
  • Cellulose
  • Polyacrylonitrile (PAN)
  • Terylene (Dacron)
  • Ethylene Glycol

Important topics

  • Classification of Polymers (Source, Structure, Polymerization Mode)
  • Addition vs. Condensation Polymerization
  • Biodegradable Polymers
  • Examples: Glycogen, Cellulose, PAN, Terylene
  • Monomers and Polymer Structures

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Questions and Solutions

Multiple Choice Questions (MCQs) - Q. 1

Q. 1. Which of the following polymers of glucose is stored by animals?
  1. Cellulose
  2. Amylose
  3. Amylopectin
  4. Glycogen
Solution: The correct option is (d) Glycogen. Glycogen serves as the primary form of glucose storage in animals, found predominantly in the liver, brain, and muscles. In contrast, cellulose is a structural polymer found in plant cell walls, while amylose and amylopectin are the two main components of starch, which is the storage polysaccharide in plants.

Multiple Choice Questions (MCQs) - Q. 2

Q. 2. Which of the following is not a semisynthetic polymer?
  1. cis-polyisoprene
  2. Cellulose nitrate
  3. Cellulose acetate
  4. Vulcanised rubber
Solution: The correct option is (a) cis-polyisoprene. This polymer is a natural rubber and is not chemically modified. Cellulose nitrate and cellulose acetate are derived from cellulose (a natural polymer) through chemical reactions, making them semisynthetic. Vulcanised rubber is natural rubber that has undergone a process of vulcanization (cross-linking with sulfur), which also classifies it as a semisynthetic polymer.

Multiple Choice Questions (MCQs) - Q. 3

Q. 3. The commercial name of polyacrylonitrile is ........
  1. dacron
  2. orlon
  3. bakelite
  4. nylon

The structure of polyacrylonitrile (PAN) is shown below:

\left[ \begin{array}{c} \mathrm{CN} \\ | \\ -\mathrm{CH}_2-\mathrm{CH}- \end{array} \right]_n

Solution: The correct option is (b) orlon. Polyacrylonitrile (PAN) is a synthetic polymer known commercially by trade names such as Orlon or Acrilan. It is produced via the addition polymerization of acrylonitrile monomer, typically initiated by peroxide catalysts. The provided chemical structure represents the repeating unit of polyacrylonitrile.

Multiple Choice Questions (MCQs) - Q. 4

Q. 4. Which of the following polymer is biodegradable?
  1. +CH_2 - C = CH - CH_2 +_n CI
  2. +CH_2 - CH = CH - CH_2 - CH_2 - CH_3 - CH_3
  3. +O - CH - CH_2 - C - O - CH - CH_2 - C +_n |
  4. +CH_2 - CH_2 +_n
Solution: The correct option is (c). The polymer represented by +O-CH-CH_2-C-O-CH-CH_2-C-\frac{1}{2} is Poly(β-hydroxybutyrate-co-β-hydroxyvalerate). This copolymer is a biodegradable polymer synthesized by certain bacteria and is used in applications where environmental degradation is desired. The other options represent polymers like PVC (a), polybutadiene (b), and polyethylene (d), which are generally not considered biodegradable.

Multiple Choice Questions (MCQs) - Q. 5

Q. 5. In which of the following polymers ethylene glycol is one of the monomer units?
  1. +OCH_2-CH_2OOC
  2. +CH_2 - CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2 + CH_2
  3. +CH_2-CH=-CH_2-CH--CH_2-
  4. +CH_2-CH_2-NH-CO-CH_2-CH_2-NH-CO+
Solution: The correct option is (a). The polymer structure +OCH_2-CH_2OOC represents Terylene (also known as Dacron). Terylene is a polyester formed through condensation polymerization. One of its monomers is ethylene glycol (HOCH_2-CH_2OH), and the other is terephthalic acid (HOOC-C_6H_4-COOH). During the polymerization process, water molecules are eliminated. The reaction involves the esterification between the hydroxyl groups of ethylene glycol and the carboxyl groups of terephthalic acid.

Common mistakes

  • Confusing the storage polymer in animals with plant-based polymers.
  • Incorrectly classifying polymers as semisynthetic when they are natural or synthetic.
  • Failing to recall commercial names associated with specific polymer structures.
  • Misidentifying the monomers used in condensation polymerization.

Revision tips

  • Create flashcards for common polymers, their monomers, and commercial names.
  • Draw out the structures of different polymer types (linear, branched, cross-linked).
  • Focus on understanding the difference between addition and condensation polymerization mechanisms.
  • Pay special attention to examples of biodegradable and semisynthetic polymers.

Practice MCQs

Q1. Which of the following polymers of glucose is primarily stored in animals?

Q2. Which of the following is NOT classified as a semisynthetic polymer?

Q3. What is the common commercial name for polyacrylonitrile (PAN)?

Q4. Which of the following polymers is biodegradable?

Q5. Ethylene glycol is a monomer unit in which of the following polymers?

Frequently asked questions

What is the main difference between natural and synthetic polymers?

Natural polymers are derived from natural sources like plants and animals (e.g., cellulose, proteins), while synthetic polymers are man-made through chemical synthesis (e.g., nylon, polyethylene).

What are semisynthetic polymers?

Semisynthetic polymers are derived from natural polymers that have been chemically modified. Examples include cellulose nitrate and vulcanised rubber.

Which polymer is used for storing glucose in animals?

Glycogen is the polymer of glucose stored by animals, primarily in the liver and muscles.

What is Terylene and what are its monomers?

Terylene, also known as Dacron, is a synthetic polyester. Its monomers are ethylene glycol and terephthalic acid.

How can we identify a biodegradable polymer?

Biodegradable polymers can be broken down by microorganisms in the environment. Poly(β-hydroxybutyrate-co-β-hydroxyvalerate) is an example discussed in the chapter.

What is the commercial name for polyacrylonitrile?

The commercial names for polyacrylonitrile (PAN) are Orlon and Acrilan.

Important links

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