Chemical ChangesTopic Summary
Knowledge Organiser: Displacement Reactions
Part of Displacement Reactions · GCSE GCSE Chemistry revision
This topic summary covers Knowledge Organiser: Displacement Reactions within Displacement Reactions for GCSE Chemistry. Revise Displacement Reactions in Chemical Changes for GCSE Chemistry with 20 exam-style questions and 20 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. 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.
Topic position
Section 13 of 13
Practice
20 questions
Recall
20 flashcards
Knowledge Organiser: Displacement Reactions
Key Terms
- Displacement: more reactive replaces less reactive
- OIL RIG: Oxidation Is Loss, Reduction Is Gain
- Spectator ion: unchanged throughout the reaction
- Ionic equation: spectator ions removed
- Exothermic: displacement reactions release heat
Must-Know Facts
- More reactive metal always displaces less reactive
- Less reactive added = no reaction
- Displacing metal is oxidised (loses electrons)
- Displaced metal ion is reduced (gains electrons)
- Mg + CuSO₄ → MgSO₄ + Cu (key example)
- Colour change: blue CuSO₄ → colourless; brown Cu forms
- Halogen displacement: Cl₂ > Br₂ > I₂
Key Equations
- Mg + CuSO₄ → MgSO₄ + Cu (metal displacement)
- Fe + CuSO₄ → FeSO₄ + Cu (iron displaces copper — second key example)
- Cu + MgSO₄ → NO REACTION (Cu less reactive than Mg)
- Mg → Mg²⁺ + 2e⁻ (oxidation half-equation)
- Cu²⁺ + 2e⁻ → Cu (reduction half-equation)
Common Mistakes
- Getting OIL RIG backwards: The displacing metal is OXIDISED (loses electrons); the metal ion being displaced is REDUCED (gains electrons)
- Saying a less reactive metal can displace a more reactive one: Displacement only works one way — more reactive always displaces less reactive
- Forgetting to balance ionic equations: Check that charge is balanced on both sides as well as atoms
- Missing spectator ions in ionic equations: Spectator ions (e.g. SO₄²⁻) do not appear in the ionic equation — only the species that change