Copper(II) oxide is a black solid. When excess dilute sulfuric acid is added to copper(II) oxide powder and the mixture is warmed, the black solid disappears and a blue solution forms. Explain what type of reaction is taking place, identifying which species is the acid and which is the base, and describe what happens to the copper(II) oxide in terms of ions formed.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Copper(II) oxide is an insoluble black powder. When it reacts with dilute sulfuric acid, the black solid dissolves to produce a blue copper(II) sulfate solution and water.
Model answer (5 marks)
The reaction is a neutralisation reaction.
The sulfuric acid is the acid – it donates H⁺ ions.
Copper(II) oxide is the base – it accepts H⁺ ions.
Copper(II) oxide releases Cu²⁺ ions into the solution.
The O²⁻ ions from CuO combine with H⁺ ions from H₂SO₄ to form water.
The sulfuric acid is the acid – it donates H⁺ ions.
Copper(II) oxide is the base – it accepts H⁺ ions.
Copper(II) oxide releases Cu²⁺ ions into the solution.
The O²⁻ ions from CuO combine with H⁺ ions from H₂SO₄ to form water.
Examiner tips
- Use the word ‘neutralisation’ to show you know the reaction type.
- Identify the acid as H₂SO₄ and the base as CuO explicitly.
- Show the ion exchange: Cu²⁺ + 2OH⁻ → Cu(OH)₂ → Cu²⁺ + 2H₂O.
- Mention that O²⁻ + 2H⁺ → H₂O to demonstrate the acid–base step.
Common mistakes
- Calling the reaction a ‘combination’ or ‘decomposition’ instead of neutralisation.
- Forgetting to state which species is the acid and which is the base.
- Not showing the formation of Cu²⁺ ions or the water from O²⁻ and H⁺.
Mark scheme (5 marks)
- The reaction is a neutralisation reaction
- The sulfuric acid is the acid (donates H⁺ / protons)
- Copper(II) oxide is the base (accepts H⁺ / protons / neutralises the acid)
- Copper(II) oxide provides / releases Cu²⁺ ions (into solution)
- The O²⁻ ions from copper(II) oxide combine with H⁺ ions from the acid to form water
Key terms in this question
Related
- All OCR A-Level Chemistry A (H432) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Acid-base and redox reactions questions
- Magnesium ribbon is added to dilute hydrochloric acid. Explain the changes in ox…
- Iron rusting is an example of an oxidation reaction. A student investigates the …
- A student adds dilute hydrochloric acid to sodium hydroxide solution. Explain wh…
- A student investigates the reaction between zinc metal and dilute sulfuric acid.…