Core Practical: Preparing Copper Sulfate (Edexcel GCSE Chemistry)

Core Practical: Preparing Copper Sulfate

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:

Hydrated copper(II) sulfate crystals should be bright blue and regularly shaped

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