Required Practical 1 - Making Salts

Question 1

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

Answer 1

• React sulfuric acid with excess 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

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 burner should be turned off or put on the safety flame when not in use
• Sulfuric acid is corrosive so wear eye protection

Question 4

What are two methods of separating mixtures?

Answer 4

-Filtration
-Crystallisation

Question 5

How can you separate an insoluble product from a solution?

Answer 5

1. 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 solids from solutions?

Answer 6

2. 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

3. 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