IB Chemistry › R3.2 › R3.2.13

The Electrochemical Series

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

Reactivity 3.2 HL Extension ⏱️ ~5 min revision
HL Extension

The Electrochemical Series Hierarchy

The electrochemical series tabulates standard reduction potentials in descending or ascending order, enabling immediate prediction of relative oxidising and reducing capabilities.

Reading the Series

How to Read the Standard Reduction Potential Series

Standard Electrochemical Reduction Series Oxidising Agents (OA) Increasing OA Strength (Gain e⁻) F₂ (Strongest) Cl₂ 2H⁺ (SHE: 0V) Zn²⁺ Li⁺ (Weakest) Standard Reduction Half-Equations F₂(g) + 2e⁻ ⇌ 2F⁻(aq) +2.87 V Cl₂(g) + 2e⁻ ⇌ 2Cl⁻(aq) +1.36 V 2H⁺(aq) + 2e⁻ ⇌ H₂(g) 0.00 V Zn²⁺(aq) + 2e⁻ ⇌ Zn(s) −0.76 V Li⁺(aq) + e⁻ ⇌ Li(s) −3.04 V ↻ Spontaneous: Top-Left + Bottom-Right Reducing Agents (RA) Increasing RA Strength (Lose e⁻) F⁻ (Weakest) Cl⁻ H₂ (SHE: 0V) Zn Li (Strongest)
HL Extension

Anti-Clockwise Spontaneity Rule

  • Top (most positive \(E^\circ\)): Strongest oxidising agents on left (e.g. \(\text{F}_2 + 2\text{e}^- \rightarrow 2\text{F}^-\), \(+2.87\text{ V}\)).
  • Bottom (most negative \(E^\circ\)): Strongest reducing agents on right (e.g. \(\text{Li}^+ + \text{e}^- \rightarrow \text{Li}\), \(-3.04\text{ V}\)).
  • Anti-clockwise rule: A species on the top-left will spontaneously react with any species below it on the right.
Exam Tip

IB Data Booklet Reduction Table Usage

In Section 24 of the IB Chemistry Data Booklet, half-equations are always written as reductions. To find the oxidation half-equation, reverse the equation from right to left.

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