NCERT Solutions for Class 12 Chemistry Chapter 15 Polymers in Hindi and English Medium updated for new academic session 2022-2023. Get here class 12 Chemistry unit 15 intext and exercises question answers in simplified format to prepare for the exams.
NCERT Solutions for Class 12 Chemistry Chapter 15
Class 12 Chemistry Chapter 15 Polymers Question Answers
A polymer is a large molecule of high molecular mass formed by the repetitive bonding of many small molecules called monomers. The process by which the monomers are transformed into polymers is called polymerisation.
Class 12 Chemistry Chapter 15 MCQ
Bakelite is an example of
The S in Buna-S refers to
Which of the following belongs to the class of natural polymers?
Which of the following is a polymer containing nitrogen?
Classification of Polymers
One of the common: Classifications of polymers is based on source from which polymer is derived.
- Natural polymers
These polymers are found in plants and animals. Examples are proteins, cellulose, starch, some resins and rubber.
- Semi-synthetic polymers
Cellulose derivatives as cellulose acetate (rayon) and cellulose nitrate, etc. are the usual examples of this sub category.
- Synthetic polymers
A variety of synthetic polymers as plastic (polythene), synthetic fibres (nylon 6, 6) and synthetic rubbers (Buna – S) are examples of man-made polymers extensively used in daily life as well as in industry.
Types of Polymerisation Reactions
There are two broad types of polymerisation reactions, i.e., the addition or chain growth polymerisation and condensation or step growth polymerisation.
Addition Polymerisation or Chain Growth Polymerisation
In this type of polymerisation, the molecules of the same monomer or diferent monomers add together on a large scale to form a polymer. The monomers used are unsaturated compounds, e.g., alkenes, alkadienes and their derivatives.
Mechanism of Addition Polymerisation
A variety of alkenes or dienes and their derivatives are polymerised in the presence of a free radical generating initiator (catalyst) like benzoyl peroxide, acetyl peroxide, tert-butyl peroxide, etc. For example, the polymerisation of ethene to polythene consists of heating or exposing to light a mixture of ethene with a small amount of benzoyl peroxide initiator. The process starts with the addition of phenyl free radical formed by the peroxide to the ethene double bond thus generating a new and larger free radical. This step is called chain initiating step.
12th Chemistry Unit 15 Multiple Choice Questions
Which of the following is called a polyamide?
Natural rubber is a polymer of
Which of the following is a condensation polymer?
Teflon, styron and neoprene are all
Some Important Addition Polymers
Polythenes are linear or slightly branched long chain molecules. These are capable of repeatedly softening on heating and hardening on cooling and are thus thermoplastic polymers.
It is prepared by the condensation polymerisation of hexamethylenediamine with adipic acid under high pressure and at high temperature. Nylon 6, 6 is fibre forming solid. It possesses high tensile strength. This characteristic can be attributed to the strong intermolecular forces like hydrogen bonding. These strong forces also lead to close packing of chains and thus impart crystalline nature. Nylon 6, 6 is used in making sheets, bristles for brushes and in textile industry.
These are the polycondensation products of dicarboxylic acids and diols. Dacron or terylene is the best known example of polyesters. It is manufactured by heating a mixture of ethylene glycol and terephthalic acid at 420 to 460 K in the presence of zinc acetate-antimony trioxide catalyst as per the reaction given earlier. Dacron fibre (terylene) is crease resistant and is used in blending with cotton and wool fibres and also as glass reinforcing materials in safety helmets, etc.
Natural rubber and Synthetic rubbers
Rubber is a natural polymer and possesses elastic properties. It is also termed as elastomeric polymer. In elastomeric polymers, the polymer chains are held together by the weak intermolecular forces.
Synthetic rubber is any vulcanisable rubber like polymer, which is capable of getting stretched to twice its length. However, it returns to its original shape and size as soon as the external stretching force is released. Thus, synthetic rubbers are either homopolymers of 1, 3 – butadiene derivatives or copolymers of 1, 3 – butadiene or its derivatives with another unsaturated monomer.
Class 12 Chemistry Chapter 15 Important Questions
What is a polymer with examples?
Polymer A substance made from long chains of repeating groups of atoms. Manufactured polymers include nylon, polyvinyl chloride (better known as PVC) and many types of plastics. Natural polymers include rubber, silk and cellulose (found in plants and used to make paper, for example).
What are polymers used?
Polymers are used in almost every area of modern living. Grocery bags, soda and water bottles, textile fibers, phones, computers, food packaging, auto parts, and toys all contain polymers. Even more-sophisticated technology uses polymers.
Why are plastics called polymers?
Plastics are polymers. A polymer is a substance made of many repeating units. The word polymer comes from two Greek words: poly, meaning many, and meros, meaning parts or units. A polymer can be thought of as a chain in which each link is the “mer,” or monomer (single unit).