Edexcel A-Level Chemistry Paper 2, November 2021: Question 7

9 marks · Medium difficulty · Extended Writing

Compare and contrast the polymerisation of cyclohexene and 4-hydroxycyclohexanecarboxylic acid, including repeat unit equations, and state three ways waste polymers can be utilised.

Practise this question

Question

Question text

This question is about polymers.

(a) Compare and contrast how each of these monomers forms a polymer.

HO C

cyclohexene 4-hydroxycyclohexanecarboxylic acid

Include equations, showing the formation of a single repeat unit for each polymer.

(6)

(b) Give three ways in which waste polymers can be utilised to improve 13

their sustainability.

(3)

Mark scheme

Show the mark scheme

Question

Answer Additional Guidance Mark

Number

*7(a) This question assesses the student’s ability to show a coherent and Guidance on how the mark scheme should be (6)

logically structured answer with linkages and fully sustained applied:

reasoning. The mark for indicative content should be added

to the mark for lines of reasoning. For example, a

Marks are awarded for indicative content and for how the answer is response with four indicative marking points that

structured and shows lines of reasoning. is partially structured with some linkages and

lines of reasoning scores 4 marks (3 marks for

The following table shows how the marks should be awarded for indicative content and 1 mark for partial structure

indicative content. and some linkages and lines of reasoning).

Number of indicative marking Number of marks awarded for If there were no linkages between the points, then

points seen in answer indicative marking points the same indicative marking points would yield an

64 overall score of 3 marks (3 marks for indicative

5-4 3 content and zero marks for linkages).

3-2 2

The following table shows how the marks should be awarded for

structure and lines of reasoning

Number of marks awarded

for structure of answer and

sustained lines of reasoning

Answer shows a coherent logical

structure with linkages and fully

sustained lines of reasoning

demonstrated throughout

Answer is partially structured

with some linkages and lines of 1

reasoning

Answer has no linkages between

points and is unstructured

Indicative content

• IP1 in both cases many monomers join (by covalent bonds Allow both polymerisations require a catalyst

to form polymers) Allow both polymers are formed from a single

type of monomer

• IP2 cyclohexene forms an addition polymer / the polymer is Allow unsaturated monomer forms saturated

formed by an addition reaction polymer

• IP3 4-hydroxycyclohexanecarboxylic acid forms a

condensation polymer / the polymer is formed by a

condensation reaction

Allow ‘only 1 product in addition but two

• IP4 no additional products from when cyclohexene products in condensation’

polymerises, but water is also formed when Allow only one functional group is needed for

4-hydroxycyclohexanecarboxylic acid polymerises addition polymerisation but two different

functional groups are needed for condensation

polymerisation

Allow cyclohexene polymerisation has 100%

atom economy, 4-hydroxycyclohexanecarboxylic

polymerisation has less than 100% atom economy

• IP5

• IP6

Ignore omitted or misplaced n in IP5 and IP6

Allow 1 IP for IP5 and IP6 if both correct repeat

units shown

Allow 2 oxygen atoms on RHS and none on LHS

for IP6 repeat unit

Question Mark

Answer Additional Guidance

Number

7(b) An answer that makes reference to the following points (3)

• recycling (1) Allow re-use

• incineration to release energy / generate electricity (1) Allow ‘use as a fuel’

• use as a feedstock (for cracking) (1) Allow ‘break down into monomers’ /

‘hydrolyse to form monomers’ / ‘break down

to form small(er) molecules’

Ignore ‘remove toxic waste gases from

incineration’ / developing biodegradable

polymers

(Total Question 7 = 9 marks)

How to answer it

Comparing Addition and Condensation Polymers & Sustainability

📌 What this question tests

This question assesses your ability to compare and contrast two major types of polymerisation (addition and condensation) using specific organic monomers (cyclohexene and 4-hydroxycyclohexanecarboxylic acid). It evaluates your chemical equations, structural drawing skills, understanding of atom economy/by-products, and knowledge of polymer sustainability strategies.

Question 7 (a)

Comparing Polymerisation Types & Equations (6 Marks)

Compare and contrast how each of these monomers forms a polymer, including equations showing the formation of a single repeat unit.

💡 Key Knowledge

Cyclohexene has a C=C double bond, making it unsaturated. It undergoes addition polymerisation where the pi bond breaks, and monomers join together with no other products formed (100% atom economy).
4-hydroxycyclohexanecarboxylic acid contains two different functional groups (-OH alcohol and -COOH carboxylic acid). It undergoes condensation polymerisation, releasing small molecules (water, H₂O) as a by-product.
Both polymerisation types involve many monomers joining via covalent bonds to form long chains.

✅ Correct Equations & Points (Indicative Content)

IP1: Many monomers join via covalent bonds.
IP2: Cyclohexene forms an addition polymer.
IP3: 4-hydroxycyclohexanecarboxylic acid forms a condensation polymer (ester linkage).
IP4: Cyclohexene has no additional products; condensation produces water.
IP5 (Equation 1): Shows n cyclohexene molecules converting to a repeat unit inside square brackets with subscript n and broken double bonds through the bracket lines.
IP6 (Equation 2): Shows n of the hydroxy-acid forming a polyester repeat unit plus n H₂O on the right-hand side.

🧠 Exam Technique (Level of Response)

This is a 6-mark extended response marked using a levels of response approach (up to 4 marks for chemistry content/indicative points, and up to 2 marks for structure, coherence, and logical linkages).

Explicitly use comparative language throughout ("whereas", "in contrast", "both require a catalyst") to secure the structural and logical reasoning marks.

❌ Common Errors

Forgetting to include the polymerisation coefficient n on both sides of the equations or misplacing the continuation bonds outside the square brackets.
Failing to show the lost water molecule ( + nH₂O ) in the condensation equation.
Treating condensation polymerisation as an addition process by leaving out the elimination product.

Mark Breakdown: 4 marks for chemical content (mapping 6 potential indicative points) + 2 marks for structured logical prose and coherent chemical explanations.

Question 7 (b)

Improving Polymer Sustainability (3 Marks)

Give three ways in which waste polymers can be utilised to improve their sustainability.

✅ Correct Answers (Acceptable Points)

Recycling / Re-use: Melting and remoulding thermoplastic waste into new shapes or products.
Incineration to generate energy / electricity: Burning waste polymers to release heat energy, which can be harnessed to generate power.
Use as a feedstock (for cracking): Breaking down waste polymers chemically (via cracking, hydrolysis, or thermal breakdown) to recover original monomers or smaller useful organic molecules.

❌ Common Errors

Vague answers like "just getting rid of them" or "burying them in landfill" (landfill directly reduces sustainability).
Mentioning "removing toxic waste gases from incineration" or "developing biodegradable polymers", which are valid eco-concepts but do not answer how waste polymers are utilised according to this mark scheme.

Mark Breakdown: 1 mark per valid utility method up to a maximum of 3 marks.

Topics

Organic Chemistry · Topic 6: Organic Chemistry I · Topic 17: Organic Chemistry II

Question and mark scheme from the Edexcel A-Level Chemistry examination, Paper 2, November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.