OCR A-Level Chemistry AS Breadth in chemistry (01), June 2024: Question 17

1 mark · Medium difficulty · Multiple Choice

Identify the correct statement about the addition polymer given its repeat unit structure.

Practise this question

Question

Multiple choice question 17 showing the repeat unit of an addition polymer inside square brackets with a backbone carbon-carbon single bond and attached groups (CH3 and H on the left carbon, Cl and H on the right carbon), with extension bonds passing through the brackets. Four options A to D follow, with option C stating that the monomer is H3CCH=CHCl. An empty box is provided for the answer.
Question text

17 The repeat unit of an addition polymer is shown below.

CH3 Cl

C C

H H

Which statement about this addition polymer is correct?

A Combustion produces toxic alkaline fumes.

B The addition polymer is biodegradable.

C The monomer is H3CCH=CHCl.

D The repeat unit above is shown as a displayed formula.

Your answer [1]

Mark scheme

Show the mark scheme Mark scheme for question 17 indicating the correct answer is C, worth 1 mark.

17 C 1

How to answer it

Evaluating Addition Polymer Properties and Monomer Structures

📌 What this question tests

This question assesses your understanding of addition polymers, the relationship between repeat units and their parent monomers, definitions of organic chemical formulae types (such as displayed vs. structural/skeletal), and the general chemical properties of polyalkenes.

Question 17 Analysis

Multiple Choice Question (Total: 1 Mark)

✅ Correct Answer: C

The monomer is H₃CCH=CHCl (1-chloropropene). Converting the repeat unit back to the monomer requires removing the single carbon-carbon backbone bond and forming a carbon-carbon double bond between the two backbone carbon atoms.

💡 Key Knowledge

  • Addition Polymers: Formed by opening the C=C double bond of unsaturated alkene monomers.
  • Deduce Monomers: To find the monomer from a repeat unit, take the two backbone carbon atoms, convert their single bond into a C=C double bond, and keep all attached groups (H, CH₃, Cl) on their respective carbons.

🧠 Exam Technique

Evaluate options systematically and eliminate incorrect statements one by one:

  • A: Combustion of halogen-containing polymers produces acidic fumes (like HCl), not alkaline fumes.
  • B: Addition polymers have strong carbon-carbon sigma backbone chains and are non-polar overall, making them non-biodegradable.
  • D: The diagram shows bonds between carbon and hydrogen explicitly drawn out as lines (e.g., C-H), but the carbon-chlorine bond is written as Cl without showing the line explicitly, and methyl groups are condensed as CH₃ . Therefore, it is a partially displayed formula, not a fully displayed one.

❌ Common Errors

  • Confusing acidic and alkaline combustion products when halogens are present in a polymer chain.
  • Failing to recognize the difference between a fully displayed formula (where every single atom and every single covalent bond must be drawn out explicitly) and a structural/partially displayed formula.
  • Incorrectly placing the double bond in the monomer during conversion.
Mark Scheme Allocation: Correct answer is C (1 mark).

Topics

Module 4: Core organic chemistry · Module 6: Organic chemistry and analysis · 4.1 Basic concepts and hydrocarbons · 6.2 Nitrogen compounds, polymers and synthesis

Question and mark scheme from the OCR A-Level Chemistry examination, AS Breadth in chemistry (01), June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.