O-LevelChemistryOrganic Chemistry5070/22 · May/June 2023 · Q107 Marks

Proteins and PET are polymers made by a reaction called condensation polymerisation.

(a)(i)The diagram in Fig. 10.1 shows the structure of a section of a protein. [Figure 10.1] Draw the general structure of the amino acid monomers used to make proteins.[1]
(a)(ii)Proteins are polyamides. Name one other polyamide.[1]
(b)(i)PET is a polymer used to make plastic bottles. The diagram in Fig. 10.2 shows the structure of PET. [Figure 10.2] Name the linkage present in PET.[1]
(b)(ii)Proteins and PET are both made by condensation polymerisation. Describe the differences between condensation polymerisation and addition polymerisation.[2]
(c)Describe two environmental challenges caused by the disposal of plastics such as PET. 1 2[2]

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Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

10(a)(i) H R O / N—C—C / H H OH (1)
10(a)(ii) nylon (1)
10(b)(i) ester (1)
10(b)(ii) any one comment about addition polymerisation
addition polymerisation (involves monomers joining together with) no other product formed (1)
addition polymer has same empirical formula as the monomer (1)
addition polymers uses monomers with a C=C bond (1)
any one comment about condensation polymerisation
condensation polymerisation involves (monomers joining together with) the formation of a simple molecule (1)
condensation polymer does not have same empirical formula as monomer(s) (1)
condensation polymerisation uses monomers with two functional groups (1)
10(c) Any two from:
Land-fills (may fill up) (1)
accumulation of plastics in oceans (1)
formation of toxic gases during burning (1)

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