OCR A-Level Chemistry AS Breadth in chemistry (01), June 2018: Question 5

1 mark · Medium difficulty · Multiple Choice

Identify which chemical equation does not represent a neutralisation reaction among the four given options.

Practise this question

Question

Multiple choice question 5 asks 'Which equation does not represent a neutralisation reaction?' with four options: A, Zn + 2HCl -> ZnCl2 + H2; B, 2NH3 + H2SO4 -> (NH4)2SO4; C, Na2CO3 + 2CH3COOH -> 2CH3COONa + CO2 + H2O; D, CuO + 2HNO3 -> Cu(NO3)2 + H2O.
Question text

5 Which equation does not represent a neutralisation reaction?

A Zn + 2HCl → ZnCl2 + H2

B 2NH3 + H2SO4 → (NH4)2SO4

C Na2CO3 + 2CH3COOH → 2CH3COONa + CO2 + H2O

D CuO + 2HNO3 → Cu(NO3)2 + H2O

Your answer [1]

Mark scheme

Show the mark scheme The mark scheme shows the correct answer for question 5 is A, worth 1 mark.

5 A 1

How to answer it

Identifying Neutralisation Reactions

What this question tests

This question assesses your ability to define and recognise a chemical neutralisation reaction. Specifically, you need to distinguish between acid-base neutralisations (which form a salt and water, or a salt, water, and carbon dioxide) and redox reactions involving acids and reactive metals.

Question Analysis & Answer

Multiple Choice Question (Part 5)

✅ Correct Answer: A

Equation A ( Zn + 2HCl → ZnCl₂ + H₂ ) is a redox reaction between an acid and a reactive metal, not a neutralisation reaction. In this reaction, zinc metal is oxidised and hydrogen ions are reduced to hydrogen gas.

💡 Key Knowledge

  • Neutralisation Definition: The reaction between hydrogen ions ( H⁺ ) and a base (such as OH⁻ , O²⁻ , CO₃²⁻ , or NH₃ ) to form a salt and water (often with CO₂ from carbonates).
  • Metal + Acid: Metals react with acids to produce a salt and hydrogen gas ( H₂ ). This is classified as a redox reaction, not a neutralisation.

🧠 Exam Technique

Scan the products of each equation first. If you spot hydrogen gas ( H₂ ) being produced from a reaction with a metal, it is a dead giveaway for a metal-acid redox reaction rather than a standard neutralisation.

❌ Common Errors

Students frequently misidentify any reaction involving an acid as a neutralisation. Remember that acids react in multiple ways, including reacting with metals to form redox systems.

Examiner Note: Option A is the correct response. Across multiple cohorts, candidates who failed this question usually confused the evolution of hydrogen gas (redox) with the formation of water (neutralisation).

Breakdown of Options B, C, and D (Why they ARE neutralisations)

Option B: 2NH₃ + H₂SO₄ → (NH₄)₂SO₄

Ammonia acts as a Brønsted-Lowry base by accepting protons from sulfuric acid to form the ammonium salt. No hydrogen gas is produced.

Option C: Na₂CO₃ + 2CH₃COOH → 2CH₃COONa + CO₂ + H₂O

Sodium carbonate is a basic salt. It reacts with ethanoic acid to form a salt, carbon dioxide, and water—a classic carbonate neutralisation.

Option D: CuO + 2HNO₃ → Cu(NO₃)₂ + H₂O

Copper(II) oxide is a metal oxide (base). It reacts with nitric acid to produce a copper salt and water.

Topics

Module 2: Foundations in chemistry · 2.1 Atoms and reactions

Question and mark scheme from the OCR A-Level Chemistry examination, AS Breadth in chemistry (01), June 2018. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.