大象传媒

What useful products can be made from acids? - OCR 21st CenturyPractical activity - producing salts

Many products require ingredients made by the reaction of acids. These include cleaning products and food additives. Acids are used on an industrial scale to produce chemicals such as fertilisers.

Part of Combined ScienceMaking useful chemicals

Practical activity - producing salts

There are a number of ways that you could produce salts in Chemistry. This is an outline of the required steps to undertake one of these methods.

It is important in this practical activity to safely use a Bunsen burner and a water bath. This includes the safe use of a range of equipment to separate and purify mixtures, including filtration and crystallisation.

Aims

To investigate the preparation of , dry hydrated copper sulfate from copper oxide.

Method

Apparatus required for the core practical involving copper sulfate

The reaction

1. Add some dilute sulfuric acid to a small beaker.

2. Add some hot water from a kettle to larger beaker or water bath. Place the beaker of sulfuric acid into the hot water to warm up the acid.

3. 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 .

Filtration

4. Fold a piece of filter paper and put it into a filter funnel. Fit the filter funnel into a conical flask.

5. Add the reaction mixture from the beaker to the filter paper.

6. Collect the , the copper sulfate . Do not collect the , the unreacted copper oxide.

7. Pour the filtrate into an evaporating basin.

Crystallisation

8. Set up a Bunsen burner, tripod and gauze on a heat resistant mat.

9. Put a beaker of water on the gauze and the evaporating basin on the beaker.

10. Heat the water, adjusting the Bunsen burner flame so the water is just simmering.

11. Stop heating before all the water in the evaporating basin leaves the copper sulfate solution.

12. Allow the evaporating basin to cool, then leave it aside for a few days or in a drying oven.

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.

Copper sulfate crystals
Image caption,
Copper sulfate crystals

Evaluation

Question

Explain why the sulfuric acid is warmed at step 2.

Question

Explain why an excess of the solid reactant is used at step 3.

Question

Describe how you could modify the method to make a pure, dry sample of an insoluble salt.

Hazards, risks and precautions

Evaluate the hazards and the precautions needed to reduce the risk of harm. For example:

HazardPossible harmPossible precaution
Sulfuric acidConcentrated acid is corrosive and damages skin and clothesUse dilute sulfuric acid
Boiling water bathSkin burnsEnsure the boiling water bath is stable on the gauze
Hot copper sulfate solution spitting out during crystallisationDamage to eyes and skinWear eye protection and avoid standing over the hot apparatus
HazardSulfuric acid
Possible harmConcentrated acid is corrosive and damages skin and clothes
Possible precautionUse dilute sulfuric acid
HazardBoiling water bath
Possible harmSkin burns
Possible precautionEnsure the boiling water bath is stable on the gauze
HazardHot copper sulfate solution spitting out during crystallisation
Possible harmDamage to eyes and skin
Possible precautionWear eye protection and avoid standing over the hot apparatus