1 - Making Salts

• How could you prepare a sample of pure, dry copper sulfate crystals from a sample of insoluble copper oxide?

  • React sulfuric acid with copper oxide
  • Filter to remove the excess copper oxide
  • Heat the solution to start evaporation
  • Turn off the heat and leave until all the water has evaporated
  • Left with copper sulfate crystals
• Write the chemical equation for the reaction between CuO and H2SO4.

  CuO + H2SO4 → CuSO4 + H2O
• What safety precautions need to be considered when preparing a pure dry salt from an insoluble compound?

  • Safety goggles - sulfuric acid is corrosive.
  • Bunsen burner turned off or put in the safety flame when not in use.
  • Tie hair back to avoid it catching fire/becoming an obstacle.
• What are two methods of separating mixtures?

  Filtration and crystallisation.
• How can you separate an insoluble product from a solution?

  Filtration:

  • Filter paper is placed in a funnel over a conical flask
  • Pour the mixture through the funnel
  • The insoluble product is left on the filter paper
• How can you separate soluble solids from solutions?

  Evaporation:

  • Place the mixture in an evaporating dish
  • Slowly heat the solution
  • The solvent evaporates and the solution becomes more concentrated so crystals will start to form
  • Keep heating the evaporating dish until you have dry crystals
• How could you separate a soluble solid from the solution if the solid decomposes when heated?

  Crystallisation:

  • Pour the solution into an evaporating dish and heat gently
  • When crystals begin to form, remove the dish from the heat and leave to cool
  • Once cooled, filter the crystals out of the solution and leave them in a warm place to dry
• What is the method for this practical?

  1. Measure 20cm3 of dilute sulfuric acid into a measuring cylinder and pour into a beaker.
  2. Heat the acid gently with a bunsen burner.
  3. Add small amounts of copper oxide to the acid until no more reacts.
  4. Filter using filter paper and funnel the solution to remove any excess copper oxide.
  5. Pour the solution into the evaporating basin.
  6. Evaporate the solution using a water bath until crystals begin to form.
  7. Leave the basin in a cool place for 24 hours.
  8. Pat the crystals dry.