IB Chemistry R3.2 R3.2.13
R3.2.13 HL

The Electrochemical Series

Ordering species by E° to predict oxidising and reducing strength.

📘 IB Understanding

Half-cells arranged in order of their E° values form the electrochemical series. This allows us to predict the relative strengths of oxidising and reducing agents.

Reading the Series

Oxidising Agents Reducing Agents F₂ (strongest) Li (strongest) Li⁺ (weakest) F⁻ (weakest) Strength increases ↑ Strength increases ↑

💡 Key Rules

  • More positive E° = stronger oxidising agent (species on left of half-equation)
  • More negative E° = stronger reducing agent (species on right of half-equation)
  • The anti-clockwise rule: the species at the top-left (strongest oxidiser) will react with the species at the bottom-right (strongest reducer)

📋 Exam Tip

In the IB data booklet, half-equations are listed as reductions. To identify the reducing agent, look at the product side (right) of the most negative E° value.

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