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    Ashadeep Iit: Answer The Following Questions (1) 2)

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    Ashadeep Iit: Answer The Following Questions (1) 2)

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    POLYMER DPP - 04.pdf

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    Ashadeep Iit: Answer The Following Questions (1) 2)

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    of 2

    ASHADEEP IIT

    Std – 12th Science Sub - Chemistry

    DPP - 04

    * ANSWER THE FOLLOWING QUESTIONS


    (1) How can you differentiate between addition and condensation polymerisation?
    (2) Write the name and structure of one of the common initiators used in free radical addition
    polymerisation.
    (3) Which of the following statements is not true about low density polythene?
    (a) Tough (b) Hard
    (c) Poor conductor of electricity (d) Highly branched structure
    (4) What is the structural difference between HDP and LDP? How does the structure account for
    different behaviour and nature, hence the use of a polymer?
    (5) Low density polythene (LDP) is used in the insulation of electricity carrying wires and manufacture
    of flexible pipes and squeeze bottles because
    (a) it is tough, hard and rigid
    (b) it is chemically inert, tough, flexible and poor conductor of electricity
    (c) it is very tough, good conductor of electricity and flexible
    (d) it is chemically inert, very soft, water absorbent and poor conductor of heat.
    (6) High density polythene is obtained by
    (a) polymerisation of ethene in a hydrocarbon solvent in the presence of Ziegler–Natta catalyst
    (b) polymerisation of ethene under high pressure and temperature
    (c) free radical polymerisation of ethene at low temperature in presence of peroxide
    (d) polymerisation of ethene in presence of carbon tetrachloride.
    (7) Which of the following is not true about high density polythene?
    (a) Tough (b) Hard (c) Inert (d) Highly branched
    (8) The difference in the densities of low density (LDP) and high density polymers (HDP) is due to the
    fact that
    (a) LDP are highly branched structures while HDP consists of closely packed linear molecules
    (b) LDP are linear chains while HDP are branched chains of polythene
    (c) both LDP and HDP are unbranched linear chains with different lengths
    (d) at high temperature, the density of polymer is reduced.
    (9) Composition of Ziegler–Natta catalyst is

    (a) (Et3)3Al  TiCl2 (b) (Me)3Al  TiCl2 (c) (Et)3Al  TiCl4 (d) (Et)3Al  PtCl4
    *****ANSWER KEY*****
    (3)(b) (5)(b) (6)(a) (7)(d) (8)(a) (9)(c)

    *****DETAILED SOLUTION*****
    (1) Sol: In addition polymerisation, the molecules of the same or different monomers add together
    to form a large polymer molecule without the elimination of simple molecules like H 2O, HCl etc.
    Condensation polymerisation is a process in which two or more bifunctional molecules undergo a
    series of condensation reactions with the elimination of some simple molecules like H 2O, HCl,
    alcohol leading to the formation of polymers.
    (2) Sol: Benzoyl peroxide
    O O
    || ||
    C6 H 5C  O  O  CC6 H 5

    (3) Sol: Low density polythene is tough but flexible (not too hard) and a poor conductor of
    electricity. It has highly branched structure.
    (4) Sol: Low density polythene (LDP) is obtained by polymerisation of ethene under high pressure of
    1000–2000 atm at a temperature of 350 K to 570 K in presence of traces of dioxygen or peroxide
    initiator. It is formed by free radical addition and has branched structure.
    LDP is chemically inert, tough, slightly flexible and poor conductor of electricity. Hence it is used for
    insulation of electric wires and manufacturing of squeeze bottles and flexible pipes.
    High density polythene (HDP) is formed by polymerisation of ethene in a hydrocarbon solvent in
    presence of Ziegler–Natta catalyst, at a pressure of 6–7 atm and temperature of 333 K to 343 K.
    HDP is a linear molecule and has high density which makes it tougher and harder. Hence it is used in
    manufacturing buckets, jars, etc.
    (5)
    (6)
    (7) Sol: High density polymer is not branched. It is made up of linear molecules which are closely
    packed.
    (8)
    (9)

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