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NEET-XII-Chemistry

06: Polymers

 page 4
 
  • Qstn #14
    How does the presence of double bonds in rubber molecules influence their

    structure and reactivity?
    Ans : Natural rubber is a linear cis-polyisoprene in which the double bonds are present between C2 and C3 of the isoprene units.



    Because of this cis-configuration, intermolecular interactions between the various strands of isoprene are quite weak. As a result, various strands in natural rubber are arranged randomly. Hence, it shows elasticity.
  • Qstn #15
    Discuss the main purpose of vulcanisation of rubber.
    Ans : Natural rubber though useful has some problems associated with its use. These limitations are discussed below:

    1. Natural rubber is quite soft and sticky at room temperature. At elevated temperatures (> 335 K), it becomes even softer. At low temperatures (< 283 K), it becomes brittle. Thus, to maintain its elasticity, natural rubber is generally used in the temperature range of 283 K-335 K.

    2. It has the capacity to absorb large amounts of water.

    3. It has low tensile strength and low resistance to abrasion.

    4. It is soluble in non-polar solvents.

    5. It is easily attacked by oxidizing agents.

    Vulcanization of natural rubber is done to improve upon all these properties. In this process, a mixture of raw rubber with sulphur and appropriate additive is heated at a temperature range between 373 K and 415 K.
  • Qstn #16
    What are the monomeric repeating units of Nylon-6 and Nylon-6, 6?
    Ans : The monomeric repeating unit of nylon 6 is, which is derived from Caprolactam.

    The monomeric repeating unit of nylon 6, 6 is, which is derived from hexamethylene diamine and adipic acid.
  • Qstn #17
    Write the names and structures of the monomers of the following polymers:
    () Buna-S () Buna-N
    () Dacron () Neoprene
    () Buna-N
    () Dacron () Neoprene
    () Buna-S () Buna-N
    () Dacron () Neoprene
    () Buna-N
    () Dacron () Neoprene
    Ans :



    Polymer
    		Monomer
    		Structure of monomer
    i
    		 Buna-S
    		 1, 3-butadiene
    Styrene
    ii
    		 Buna-N
    		 1, 3-butadiene
    Acrylonitrile
    iii
    		 Neoprene
    		 Chloroprene
    iv
    		 Dacron
    		 Ethylene glycol
    Terephthalic acid


    () () () () () () () () () () () () () ()
  • Qstn #17-i
    Buna-S () Buna-N
    () Dacron () Neoprene
    Ans : () () ()
  • Qstn #18
    Identify the monomer in the following polymeric structures.
    ()
    ()
    ()
    ()
    Ans : null () The monomers of the given polymeric structure are decanoic acid and hexamethylene diamine .
    () The monomers of the given polymeric structure are


    () The monomers of the given polymeric structure are decanoic acid and hexamethylene diamine .
    () The monomers of the given polymeric structure are


  • Ans : The monomers of the given polymeric structure are decanoic acid and hexamethylene diamine .
  • Ans : The monomers of the given polymeric structure are


  • Qstn #19
    How is dacron obtained from ethylene glycol and terephthalic acid?
    Ans : The condensation polymerisation of ethylene glycol and terephthalic acid leads to the formation of dacron.


  • Qstn #20
    What is a biodegradable polymer? Give an example of a biodegradable aliphatic polyester.
    Ans : A polymer that can be decomposed by bacteria is called a biodegradable polymer.

    Poly-β-hydroxybutyrate-CO-β- hydroxyvalerate (PHBV) is a biodegradable aliphatic polyester.


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