📘 IB Understanding
An oxidising agent accepts electrons (gets reduced). A reducing agent donates electrons (gets oxidised). Use the mnemonic OIL RIG: Oxidation Is Loss, Reduction Is Gain.
Key Definitions
| Term | What It Does | What Happens to It |
|---|---|---|
| Oxidising agent | Causes oxidation in another species | Gets reduced (gains e-) |
| Reducing agent | Causes reduction in another species | Gets oxidised (loses e-) |
Example: Halogen Displacement
Cl2(aq) + 2Br-(aq) → 2Cl-(aq) + Br2(aq)
Identifying the Agents
- Cl2 gains electrons (0 → -1): it is the oxidising agent
- Br- loses electrons (-1 → 0): it is the reducing agent
Writing Half-Equations
Splitting the Reaction
- Reduction: Cl2 + 2e- → 2Cl-
- Oxidation: 2Br- → Br2 + 2e-
⚠️ Exam Tip
When identifying agents, always name the entire substance (e.g. "chlorine" or "bromide ions"), not just the atom.
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