CBSE Class 12 Chemistry Chapter 15: Polymers NCERT Solutions

Solution: Polymers are large, high molecular mass macromolecules that are formed by the repetition of smaller structural units called monomers. These monomers are chemically bonded together to form long chains. Polymers can have molecular masses ranging from thousands to millions of atomic mass units ($10^3\; -\; 10^7\; u$). They can be found in nature (natural polymers) or synthesized in laboratories (synthetic polymers). Common examples include polythene, rubber, and nylon 6, 6.

Solution: Polymers can be classified into three main types based on their structural arrangement:

1. Linear polymers: These polymers consist of long, straight, and unbranched chains of repeating monomer units. They can be visualized as simple chains. Examples include high-density polythene (HDP) and polyvinyl chloride.

   

2. Branched chain polymers: These polymers are characterized by a main polymer chain that has shorter side chains or branches attached to it. They are essentially linear chains with additional branches. Examples include low-density polythene (LDP) and amylopectin.

   

3. Cross-linked or Network polymers: In these polymers, different linear polymer chains are joined together by covalent bonds, forming a three-dimensional network structure. This cross-linking often involves bi-functional or tri-functional monomers, leading to a rigid and strong structure. Examples include Bakelite and Melmac.

   

Solution:

1. The polymer $$\backslash left\backslash \{\backslash operatorname\{CF\}\_\{2\}-\backslash operatorname\{CF\}\_\{2\}\backslash right\backslash \}\_\{n\}$$ is Polytetrafluoroethene (PTFE), commonly known as Teflon. Its monomer is Tetrafluoroethene ($$\backslash mathrm\{CF\}\_\{2\}=\backslash mathrm\{CF\}\_\{2\}$$).
2. The polymer $$\backslash left\backslash \{\backslash mathrm\{NH\}-\backslash left(\backslash mathrm\{CH\}\_\{2\}\backslash right)\_\{6\}-\backslash mathrm\{NH\}-\backslash mathrm\{CO\}-\backslash left(\backslash mathrm\{CH\}\_\{2\}\backslash right)\_\{4\}-\backslash mathrm\{CO\}\backslash right\backslash \}\_\{n\}$$ is Nylon 6,6. Its monomers are Hexamethylenediamine ($$\backslash mathrm\{H\}\_\{2\}\; \backslash mathrm\{~N\}-\backslash left(\backslash mathrm\{CH\}\_\{2\}\backslash right)\_\{6\}-\backslash mathrm\{NH\}\_\{2\}$$) and Adipic acid ($$\backslash mathrm\{HOOC\}-\backslash left(\backslash mathrm\{CH\}\_\{2\}\backslash right)\_\{4\}-\backslash mathrm\{COOH\}$$).
3. The polymer $$\backslash left\backslash \{\backslash mathrm\{NH\}-\backslash mathrm\{CH\}\_\{2\}-\backslash mathrm\{CO\}\backslash right\backslash \}\_\{n\}$$ is Nylon 6. Its monomer is Caprolactam.

Solution: The classification of the given polymers is as follows:

Addition polymers: These polymers are formed by the repeated addition of monomers without the loss of any small molecules. The monomers usually contain a double bond.

• Polyvinyl chloride (formed from vinyl chloride)
• Polythene (formed from ethene)

Condensation polymers: These polymers are formed when two different monomers (or the same monomer with two different functional groups) react with each other to form a larger structural unit, with the simultaneous elimination of small molecules like water, ammonia, or methanol.

• Terylene (formed from ethylene glycol and terephthalic acid, with elimination of water)
• Bakelite (formed from phenol and formaldehyde, with elimination of water)