Describe how a pure, dry sample of copper(II) sulfate crystals could be prepared starting from copper(II) oxide and dilute sulfuric acid.

Cambridge International IGCSE Chemistry (0620) — 7.3 Preparation of salts · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Add excess copper(II) oxide to dilute sulphuric acid and stir until the solid dissolves.
Filter the mixture to remove any unreacted copper(II) oxide.
Heat the filtrate to evaporate water and concentrate the solution.
Cool the concentrated solution; copper(II) sulfate crystals will precipitate, which are then collected and dried.

Examiner tips

  • Use the word ‘add’ and ‘filter’ to show the steps clearly. Show that the copper(II) oxide reacts to give CuSO₄(aq). Mention that excess solid is removed by filtration. Explain that heating removes water and cooling induces crystallisation.
  • common_mistakes
  • :
  • Writing the reaction as CuO + H₂SO₄ → CuSO₄ + H₂O without indicating excess CuO. Forgetting to filter out the unreacted solid. Not stating that cooling is required for crystal formation.

Mark scheme (4 marks)

  1. Add excess copper(II) oxide to the dilute sulfuric acid
  2. Filter to remove the excess (unreacted) copper(II) oxide
  3. Heat / evaporate the filtrate to concentrate the solution
  4. Allow the solution to cool so that copper(II) sulfate crystals form, then dry the crystals

Related

More Preparation of salts questions

▶ Try answering this question with AI marking (free) →