Required practical 1 - Making salts

Question 1

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

Answer 1

1) React sulfuric acid with excess copper oxide.
2) Filter to remove the excess copper oxide.
3) Heat the solution to start evaporation.
4) Turn off the heat and leave until all the water has evaporated.
5) Left with copper sulphate crystals.

Question 2

Write the chemical equation for the reaction between CuO and H₂SO₄

Answer 2

CuO + H₂SO₄ → CuSO₄ + H₂O

Question 3

What safety precautions need to be considered when preparing a pure, dry salt from an insoluble compound?

Answer 3

• Bunsen burned should be turned off or put on the safety flame when not in use.
• Wear eye protection as sulfuric acid is corrosive.

Question 4

What are 2 methods of separating mixtures?

Answer 4

Filtration and crystillisation.

Question 5

How can you separate an insoluble product from a solution?

Answer 5

Filtration:

• Filter paper placed in a funnel over a conical flask.
• Pour mixture through the funnel.
• Insoluble product left on the filter paper.

Question 6

How can you separate soluble solid from solutions?

Answer 6

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.

Question 7

How could you separate a soluble solid from a solution, if the solid decomposes when heated?

Answer 7

Crystallisation:

• Pour the solution into an evaporating dish and heat gently.
• When the crystals start to form, remove the dish from the heat and leave to cool.
• Once cold, filter the crystals out of the solution and leave them in a warm place to dry.