RP1: Making Salts

Question 1

What is the aim of the experiment?

Answer 1

• prep of a pure, dry sample of a soluble salt from an insoluble oxide or carbonate using a Bunsen burner to heat dilute acid and a water bath or electric heater to evaporate the solution

Question 2

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

Answer 2

1) measure 40cm³ sulfuric acid into beaker
2) set up tripod, gauze and heatproof mat. heat acid gently using Bunsen burner until it is almost boiling. turn off Bunsen burner
3) using spatula, add small amounts of copper (II) oxide powder at a time, stirring with glass rod. continue to do this if, after stirring, black powder disappears and solution is clear blue
4) stop adding when some black powder remains after stirring
5) set up filter funnel and paper over conical flask, using clamp stand to hold funnel. filter contents of beaker.
6) when filtration is complete, pour contents of conical flask into evaporating basin. evaporate gently using a water bath on the tripod and gauze until around half the solution remains
7) transfer remaining solution to crystallising dish. leave in cool place for at least 24 hours
8) remove crystals from concentrated solution with spatula and gently pat dry between two pieces of filter paper. these are pure dry crystals of copper (II) sulfate

Question 3

What are the potential risks?

Answer 3

• do not boil the acid; the resulting frothing of copper (II) oxide may go over the top of the beaker

Question 4

What safety precautions should be taken?

Answer 4

• Wear safety goggles as sulphuric acid is corrosive.
• Make sure hair is tied back.
• When the Bunsen burner is not in use, turn it off or leave it on the orange safety flame.

Question 5

State the chemical equation for the reaction between CuO and H2SO4

Answer 5

• CuO + H2SO4 —> CuSO4 + H2O