Preparing Salts
Year 8 🧪 Acids, Bases & Salts Describe methods for preparing soluble and insoluble salts.
🧂 Methods of Salt Preparation
| Salt type | Method | Example |
|---|---|---|
| Soluble (acid + insoluble base) | Add excess base to warm acid; filter; evaporate; crystallise | CuSO₄ from CuO + H₂SO₄ |
| Soluble (acid + alkali) | Titration; evaporate; crystallise | NaCl from HCl + NaOH |
| Insoluble salt | Precipitation (mix two solutions) | BaSO₄ from BaCl₂ + Na₂SO₄ |
🔬 Making Copper Sulfate
Copper sulfate (CuSO₄) is made by reacting copper oxide (insoluble base) with dilute sulfuric acid.
- Warm dilute H₂SO₄ gently (do not boil).
- Add excess CuO (black powder) — all acid reacts.
- Filter to remove excess CuO.
- Gently evaporate filtrate to concentrate.
- Cool to crystallise blue CuSO₄·5H₂O crystals.
- Filter and dry crystals gently at room temperature.
💧 Crystallisation & Precipitation
Copper Sulfate
$$\text{CuO}(s) + \text{H}_2\text{SO}_4(aq) \rightarrow \text{CuSO}_4(aq) + \text{H}_2\text{O}(l)$$Precipitation: BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s)↓ + 2NaCl(aq)
Filter and wash the BaSO₄ precipitate to obtain the insoluble salt.
Filter and wash the BaSO₄ precipitate to obtain the insoluble salt.
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Interactive Demonstration — Preparing Salts
Choose the correct method to prepare each salt.
Select the preparation method.
🧂 Salt Preparation Guide
Calculate moles and mass of salt produced from acid + base.