RP1 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 evaportation
• 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 are two methods of separating mixture?

Answer 3

filteration
crystallisation

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

how can you separate an insoluble product from a solution?

Answer 4

filtration:
- filter paper placed in a funnel over a conical flask
- pour mixture through the funnel
- insoluble product left on the filter paper

Question 4

how can you separate soluble solids from solutions?

Answer 4

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 4

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

Answer 4

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