CIE A Level Chemistry (9701) exams from 2022

Revision Notes

7.7.3 Repeat Units & Monomers

Deducing the Repeat Unit of a Condensation Polymer

  • In condensation polymerisation the monomers either contain 2 of the same functional group or one single monomer has both functional groups needed for polymerisation
    • For example Diamine and dicarboxylic acid
    • Or an aminocarboxylic acid
  • When presented with 2 monomers there are steps to take in order to deduce the repeat unit of a condensation polymer

Exam Tip

  • Remember: in condensation polymerisation, a small molecule is expelled as a result of the 2 monomers joining together.
  • When a dioic acid and diamine polymerise, a water molecule is expelled
    • OH from acid and H from the amine
  • When a dioyl acid and diamine are polymerised, a hydrochloric acid molecule is expelled
    • Cl from the dioyl acid and H from the amine

Identifying Monomers in Condensation Polymers

  • When a section of polymer is presented, the monomers can be identified by considering the small molecules expelled from the monomers
  • If a water molecule is expelled, the -OH must have been from an acid group
  • The hydrogen atom may be from an amine group of a monomer.
  • If the molecule was hydrochloric acid (HCl), a dioyl chloride monomer may have been used

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.

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