Core practical
Making copper sulfate crystals
There are a number of ways that you could make copper sulfate crystals in Chemistry. This is an outline of the required steps to undertake one of these methods.
Aims
To investigate the preparation of pure, dry hydrated copper sulfate crystals starting from copper oxide.
Method
- Place some sulfuric acid in a conical flask and warm it in a water bath.
- Add a spatula of copper oxide powder to the acid and stir with a glass rod.
- Continue adding copper oxide powder until it is in In chemistry, a substance is in excess if there is more than enough of it to react with another reactant..
- Filter the mixture to remove the excess copper oxide.
- Pour the filtrate (the copper sulfate solution) into an evaporating basin.
- Heat the copper sulfate solution to evaporate half of the water.
- Pour the solution into a watch glass and leave to allow all of the water to evaporate.
Results
Record the appearance of the copper sulfate crystals, including their colour and shape.
Analysis
Hydrated copper sulfate crystals should be blue and regularly shaped. Describe how your crystals compare to this description. Suggest an explanation for any differences.
Evaluation
Question
Explain why the sulfuric acid is warmed in a water bath in step 1.
Warm acid will react faster than cold acid, helping to make sure that all the acid reacts with the copper oxide.
Hazards, risks and precautions
It is important in this practical activity to use appropriate apparatus and methods. This includes the safe use and careful handling of substances and equipment.
Evaluate the hazards and the precautions needed to reduce the risk of harm. For example:
| Hazard | Possible harm | Precaution |
| Sulfuric acid | Concentrated acid is corrosive and damages skin and clothes | Use dilute sulfuric acid |
| Boiling water bath | Skin burns | Ensure the boiling water bath is stable |
| Hot copper sulfate solution spitting out during crystallisation | Damage to eyes and skin | Wear eye protection and avoid standing over the hot apparatus |
| Hazard | Sulfuric acid |
|---|---|
| Possible harm | Concentrated acid is corrosive and damages skin and clothes |
| Precaution | Use dilute sulfuric acid |
| Hazard | Boiling water bath |
|---|---|
| Possible harm | Skin burns |
| Precaution | Ensure the boiling water bath is stable |
| Hazard | Hot copper sulfate solution spitting out during crystallisation |
|---|---|
| Possible harm | Damage to eyes and skin |
| Precaution | Wear eye protection and avoid standing over the hot apparatus |