This topic summary covers Knowledge Organiser: Oxidation and Reduction (Redox) within Oxidation & Reduction for GCSE Chemistry. Revise Oxidation & Reduction 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 14 of 14 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Oxidation and Reduction (Redox)
Key Terms
- Oxidation: loss of electrons (OIL)
- Reduction: gain of electrons (RIG)
- Redox: both occur simultaneously
- Reducing agent: donates electrons (is itself oxidised)
- Oxidising agent: accepts electrons (is itself reduced)
- OIL RIG / LEO GER: key mnemonics
Must-Know Facts
- Oxidation and reduction always happen together
- Oxidation = loss of e⁻ OR gain of O OR loss of H
- Reduction = gain of e⁻ OR loss of O OR gain of H
- Half equations: e⁻ on right (oxidation), left (reduction)
- Anode = oxidation; Cathode = reduction (OARC)
- Displacement, combustion, rusting = all redox
Key Equations
- Mg → Mg²⁺ + 2e⁻ (oxidation half-equation)
- Cu²⁺ + 2e⁻ → Cu (reduction half-equation)
- 2Fe₂O₃ + 3C → 4Fe + 3CO₂ (reduction of iron oxide by carbon)
Common Mistakes
- Confusing the reducing agent and oxidising agent: The reducing agent DONATES electrons (is itself oxidised); the oxidising agent ACCEPTS electrons (is itself reduced)
- Saying only electron transfer counts as redox: Redox also includes gaining/losing oxygen or hydrogen — combustion and rusting are redox reactions
- Writing half-equations with unbalanced charges: Both atoms and charges must balance — check the total charge on each side matches
- Forgetting OARC: At the Anode = Oxidation; at the Cathode = Reduction — applies to electrolysis and electrochemical cells
Practice questions for Oxidation & Reduction
What does OIL stand for in the mnemonic OIL RIG?
In the reaction Mg + CuSO₄ → MgSO₄ + Cu, identify which species is oxidised and which is reduced. (2 marks)
Quick recall flashcards
What does OIL RIG stand for?
Oxidation Is Loss (of electrons)
Reduction Is Gain (of electrons)
What is a redox reaction?
A reaction where oxidation and reduction happen simultaneously