IGCSE Chemistry: Redox Reactions – Exam Tips & Revision Guide
This guide covers IGCSE Chemistry redox reactions. You will revise oxidation (loss of electrons; gain of oxygen), reduction (gain of electrons; loss of oxygen), OIL RIG (Oxidation Is Loss, Reduction Is Gain of electrons), and oxidising and reducing agents.
Key concepts to revise
- Oxidation – Loss of electrons; gain of oxygen; increase in oxidation number (if used).
- Reduction – Gain of electrons; loss of oxygen; decrease in oxidation number.
- Redox – Both oxidation and reduction occur in the same reaction; one species loses electrons (oxidised), another gains (reduced).
- Oxidising agent – Accepts electrons; is reduced. Reducing agent – Donates electrons; is oxidised.
Exam tips and command words
- State – Whether a species is oxidised or reduced (loss or gain of electrons/oxygen).
- Identify – The oxidising agent (the one that is reduced) and the reducing agent (the one that is oxidised).
- Describe – What happens to the oxidation state or electrons in a half-equation.
- Write – Half-equations for oxidation (e.g. Mg → Mg2+ + 2e-) and reduction (e.g. Cu2+ + 2e- → Cu).
Common mistakes
- Confusing oxidising agent (gets reduced) with reducing agent (gets oxidised).
- Saying “oxygen is oxidised” (oxygen is often the oxidising agent; it is reduced to O2- or in compounds).
- Not balancing half-equations (same number of electrons lost and gained when combining).
Revision checklist
- Define oxidation and reduction in terms of electrons (OIL RIG) and in terms of oxygen.
- Identify which species is oxidised and which is reduced in a given reaction (e.g. displacement).
- State the oxidising agent and reducing agent in a reaction.
- Write simple half-equations (e.g. Fe → Fe2+ + 2e-; Cl2 + 2e- → 2Cl-).
Next steps
Book a free trial with an IGCSE Chemistry tutor to practise redox questions, or explore Tutopiya’s learning portal for more revision resources.
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