This topic summary covers Knowledge Organiser: Making Salts within Making Salts for GCSE Chemistry. Revise Making Salts in Chemical Changes for GCSE Chemistry with 20 exam-style questions and 20 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 13 of 13 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Making Salts
Key Terms
- Crystallisation: forming crystals by cooling concentrated solution
- Filtration: removing insoluble solid from liquid
- Evaporation: removing water to concentrate solution
- Precipitation: forming insoluble solid by mixing two solutions
- Excess: more than needed to react completely
Must-Know Facts
- Soluble salt: react acid + insoluble base with excess base; filter, evaporate, cool, dry
- Insoluble salt: mix two solutions; filter precipitate; wash with distilled water; dry
- All nitrates are soluble; all Na/K/NH₄ salts are soluble
- Insoluble: AgCl (white), BaSO₄ (white), PbI₂ (yellow)
- Add EXCESS BASE not excess acid
- FECD: Filter, Evaporate, Cool, Dry
Key Equations
- CuO + H₂SO₄ → CuSO₄ + H₂O (insoluble base + acid → soluble salt)
- BaCl₂ + Na₂SO₄ → BaSO₄↓ + 2NaCl (precipitation)
- AgNO₃ + NaCl → AgCl↓ + NaNO₃ (silver chloride precipitation)
Common Mistakes
- Using excess acid instead of excess base: Always add excess BASE — if excess acid is present, the salt solution will be contaminated and evaporation won't remove it
- Filtering before evaporating for soluble salts: For soluble salt preparation, filter FIRST (to remove excess solid) then evaporate and crystallise
- Confusing soluble and insoluble salt methods: Insoluble salts use precipitation (mix two solutions); soluble salts use acid + excess insoluble base then FECD
- Forgetting to wash the precipitate: When making insoluble salts, wash with distilled water to remove soluble impurities before drying
Practice questions for Making Salts
Which of the following is the correct method for making copper sulfate crystals from copper oxide and sulfuric acid?
Describe the steps involved in the required practical for preparing a pure, dry sample of copper sulfate crystals from copper oxide and dilute sulfuric acid.
Quick recall flashcards
What is crystallisation?
The process of forming solid crystals from a saturated solution
What colour is copper sulfate?
Blue (as crystals and in solution)