OCR A-Level Chemistry Periodic table, elements and physical chemistry (01), June 2024: Question 5

1 mark · Easy difficulty · Multiple Choice

Identify the statement that explains the trend in boiling points down the halogens group.

Practise this question

Question

Multiple choice question 5 asking which statement explains the trend in boiling points down the halogens group, with options A (bond enthalpy increases), B (halogens become less electronegative), C (induced dipole-dipole interactions become stronger), and D (reactivity decreases).
Question text

5 Which statement explains the trend in boiling points down the halogens group?

A The bond enthalpy of the covalent bonds increases.

B The halogens become less electronegative.

C The induced dipole–dipole interactions (London forces) become stronger.

D The reactivity of the halogens decreases.

Your answer [1]

Mark scheme

Show the mark scheme Mark scheme indicating the correct answer for question 5 is C, worth 1 mark.

5 C 1

How to answer it

Halogen Boiling Points Trend

What this question tests

This question assesses your understanding of intermolecular forces in Group 7 (halogens). Specifically, it tests your ability to link physical properties (boiling points) down a group to the changing strength of induced dipole-dipole interactions (London forces) caused by increasing molecular size and number of electrons.

Question 5

Multiple Choice Analysis

✅ Correct Answer: C

As you go down Group 7 from fluorine to iodine, molecules become larger with more electrons. This leads to stronger induced dipole-dipole interactions (London forces) between molecules, requiring more thermal energy to overcome during boiling.

💡 Key Knowledge

  • Halogens exist as diatomic molecules (F₂, Cl₂, Br₂, I₂).
  • Boiling involves overcoming intermolecular forces, not covalent bonds.
  • Down the group: atomic radius increases, electron number increases, and London forces become stronger.

🧠 Exam Technique

Read multiple-choice questions carefully to distinguish between intramolecular properties (like covalent bond enthalpy) and intermolecular properties (like boiling points and London forces).

❌ Common Errors

  • Choosing A: Confusing boiling with thermal decomposition. Boiling breaks intermolecular forces, whereas covalent bond enthalpy refers to breaking intramolecular covalent bonds.
  • Choosing B or D: Mixing up periodic trends in electronegativity or chemical reactivity with physical properties like boiling points.
Mark Allocation: 1 mark for selecting C.

Topics

Module 3: Periodic table and energy · 3.1 The periodic table

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