Core Practical: Preparing Copper Sulfate (Edexcel GCSE Chemistry: Combined Science)

Aim:

To prepare a pure, dry sample of hydrated copper(II) sulfate crystals

Materials:

• 1.0 mol / dm³ dilute sulfuric acid
• Copper(II) oxide
• Spatula & glass rod
• Measuring cylinder & 100 cm³ beaker
• Bunsen burner
• Tripod, gauze & heatproof mat
• Filter funnel & paper, conical flask
• Evaporating basin and dish.

The preparation of copper(II) sulfate by the insoluble base method

Practical Tip:

The base is added in excess to use up all of the acid, which would become dangerously concentrated during the evaporation and crystallisation stages

Method:

1. Add 50 cm³ dilute acid into a beaker and warm gently using a Bunsen burner
2. Add the copper(II) oxide slowly to the hot dilute acid and stir until the base is in excess (i.e. until the base stops dissolving and a suspension of the base forms in the acid)
3. Filter the mixture into an evaporating basin to remove the excess base
4. Gently heat the solution in a water bath or with an electric heater to evaporate the water and to make the solution saturated
5. Check the solution is saturated by dipping a cold glass rod into the solution and seeing if crystals form on the end
6. Leave the filtrate in a warm place to dry and crystallise
7. Decant excess solution and allow the crystals to dry

Results:

Hazards, risks and precautions

Hazard symbols to show substances that are corrosive, harmful to health and hazardous to the environment

• Copper(II) oxide and solid copper(II) sulfate can cause serious eye irritation and is a skin irritant. It is harmful if swallowed or inhaled and is toxic to aquatic life
• For all substances, avoid contact with the skin and use safety goggles
• For copper(II) oxide, care should be taken not to breathe in the powder