OCR A-Level Chemistry AS Breadth in chemistry (01), June 2024: Question 5

1 mark · Medium difficulty · Multiple Choice

Identify which reaction produces a product with linear molecules from a given set of chemical equations.

Practise this question

Question

Multiple choice question 5 asks which reaction produces a product with linear molecules, with options A (2B + 3F2), B (C + O2), C (2H2 + O2), and D (N2 + 3H2). Below the options is an answer box and the mark allocation [1].
Question text

5 Which reaction produces a product with linear molecules?

A 2B + 3F2

B C + O2

C 2H2 + O2

D N2 + 3H2

Your answer [1]

Mark scheme

Show the mark scheme The mark scheme indicates that the correct answer for question 5 is B, worth 1 mark.

5 B 1

How to answer it

Predicting Molecular Shapes from Reactions

📌 What this question tests

This question assesses your ability to deduce the formula of reaction products, apply Electron Pair Repulsion Theory (VSEPR), and recognise standard molecular shapes (specifically linear geometry) based on bonding and lone pairs around a central atom.

Question 5 Analysis

Identifying Linear Molecules in Chemical Reactions

✅ Correct Answer: B

Reaction B is C + O₂ → CO₂ . Carbon dioxide ( CO₂ ) contains a central carbon double-bonded to two oxygen atoms, resulting in 2 regions of electron density and a linear shape (180° bond angle).

💡 Key Knowledge (VSEPR Theory)

  • Boron trifluoride ( BF₃ ) from A: Trigonal planar (3 bond pairs, 0 lone pairs).
  • Water ( H₂O ) from C: Non-linear / bent (2 bond pairs, 2 lone pairs).
  • Ammonia ( NH₃ ) from D: Trigonal pyramidal (3 bond pairs, 1 lone pair).

🧠 Exam Technique

Do not just guess based on the reagents! Quickly write out the balanced equations for each option to identify the exact product formed before determining its shape.

❌ Common Errors

Students frequently confuse the shape of H₂O (Option C) with linear because it has three atoms, forgetting that oxygen retains two lone pairs that push the bonds downward into a bent geometry.

Mark Allocation: [1] mark awarded for selecting option B.

Topics

Module 2: Foundations in chemistry · 2.2 Electrons, bonding and structure

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.