AQA A-Level Chemistry Paper 3, 2024: Question 32

✅ Correct answer (1 mark)

B — a polyamide

To score the mark: select B . No explanation is required for MCQ, but your revision should focus on the “why”.

💡 Key knowledge: what enables hydrogen bonding?

• Hydrogen bonding needs:
  • a δ⁺ H bonded to N, O or F (a “donor”), and
  • a lone pair on N, O or F (an “acceptor”).
• Polyamides contain the amide link: –CONH–
  • N–H provides the H-bond donor.
  • C=O oxygen provides the H-bond acceptor.
• Therefore polyamide chains can form strong intermolecular hydrogen bonds between chains.

🧠 Exam technique: how to answer in under 10 seconds

• Scan the options for –NH– in the repeat unit (or the word amide).
• If the polymer has N–H and a lone pair acceptor (usually O in C=O), it’s a hydrogen-bonding polymer.
• Don’t overthink: AQA often tests the “headline” intermolecular force for each polymer family.

❌ Common errors (and why they lose marks)

• Choosing polyester (D) because it has oxygen atoms:
  • Polyesters have –COO– (acceptors) but no O–H or N–H, so they cannot hydrogen bond to each other strongly in the same way.
• Choosing polychloroalkene (C) due to polarity:
  • C–Cl gives dipole–dipole forces, but not hydrogen bonding (H must be bonded to N/O/F).
• Choosing polyalkene (A) assuming “all big molecules stick together”:
  • Polyalkenes are essentially non-polar → mainly London forces; no suitable groups for hydrogen bonding.

Polyalkene

• Typical link: –CH₂–CH(R)–
• Main IMF: London forces
• Hydrogen bonding? No

Polychloroalkene

• Contains C–Cl (polar bond)
• Main IMF: dipole–dipole + London
• Hydrogen bonding? No (no H–N/O/F)

Polyester

• Link: –COO–
• Has acceptors (O lone pairs) but no donor
• Hydrogen bonding between chains? Not significant / no

Polyamide (correct)

• Link: –CONH–
• Donor: N–H and acceptor: C=O
• Hydrogen bonding between chains? Yes