Making Salts

Making Soluble Salts Using the Excess Solid Method

- To make a soluble salt, you need to react an acid with an insoluble base (often metal oxide/metal hydroxide).

Making Hydrated CuSO₄:

1. Put some sulphuric acid into a beaker.
2. Warm gently over a Bunsen burner to speed up the reaction.
3. Add small amounts of copper oxide at a time until no more reaction takes place (ensuring all H₂SO₄ reacted).
→ A blue solution is formed with excess black solid—CuO.
4. Filter residue into a different beaker and pour the filtrate into an evapourating dish.
5. Evaporate 2/3 of the water from the solution using a Bunsen burner.
6. Leave to cool and crystallise.
7. Filter off crystals between pieces of filter paper.

For Anhydrous CuSO₄:

→ Heat to dryness—no waters of crystallisation.

Making Insoluble Salts by Precipitation:

- To make an insoluble salt, you need to mix/react the right 2 soluble salts.

- Making insoluble salts by precipitation:

- To make an insoluble salt, you need to mix/react the right two soluble salts.

Preparing Lead Sulfate:

1. Mix lead (II) nitrate solution with sodium sulfate solution and stir.
2. Filter the mixture to keep residue/precipitation.
3. Use distilled water to wash the ppt, ensuring it removes all soluble magnesium sulphate.
4. Place PPT on filter paper (fresh) and leave to dry in a desiccator.

- Swirl the beaker with more deionised water and tip it into filter paper to ensure all precipitate is removed.

- The soluble lead nitrate solution reacted with the soluble sodium sulfate solution.
- Pb²⁺ ions bonded with SO₄^2- ions to form ppt PbSO₄.
- Mg²⁺ ions + NO₃^- ions remain in solution, forming Mg(NO₃)₂.