Oxidation & Reduction
Year 10 (IGCSE) ⚗️ Chemical Reactions Define redox using electron transfer; assign oxidation states; apply OIL RIG.
🔄 OIL RIG
Oxidation and reduction always occur together in redox reactions.
OIL RIG
$$\text{Oxidation = Loss of electrons} \quad \text{Reduction = Gain of electrons}$$2Mg + O₂ → 2MgO: Mg: 0 → +2 (oxidised). O: 0 → −2 (reduced).
📊 Oxidation States
Oxidation state (number) shows the effective charge on an atom in a compound.
Rules:
• Free elements: oxidation state = 0
• O = −2 (usually); H = +1 (usually)
• Sum of oxidation states = overall charge
Find S in H₂SO₄: 2(+1) + S + 4(−2) = 0 → S = +6
• Free elements: oxidation state = 0
• O = −2 (usually); H = +1 (usually)
• Sum of oxidation states = overall charge
Find S in H₂SO₄: 2(+1) + S + 4(−2) = 0 → S = +6
⚗️ Oxidising & Reducing Agents
Definitions
$$\text{Oxidising agent: gains electrons (is reduced)}$$
$$\text{Reducing agent: loses electrons (is oxidised)}$$Fe + CuSO₄ → FeSO₄ + Cu:
Fe (0→+2): oxidised → reducing agent.
Cu²⁺ (+2→0): reduced → oxidising agent.
Fe (0→+2): oxidised → reducing agent.
Cu²⁺ (+2→0): reduced → oxidising agent.
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Interactive Demonstration — Oxidation & Reduction
OIL RIG — Oxidation Is Loss, Reduction Is Gain (of electrons). Assign oxidation states.
Identify what is oxidised and what is reduced.
🔄 Oxidation State Calculator
Calculate the oxidation state of an element in a compound.