3.2.12 (HL)—Standard electrode potential (E⦵)

$E°(SHE) = 0 V by convention$

Use reduction-form data: a more positive E° means greater tendency to be reduced and stronger oxidizing behaviour. A very negative metal reduction potential indicates ease of reverse oxidation and strong reducing behaviour.

The standard hydrogen electrode uses H₂(g) at 100 kPa in contact with aqueous H⁺ of unit activity (commonly represented as 1 mol dm⁻³) at 298 K on an inert platinum surface, and is assigned E° = 0.00 V. Pair an unknown half-cell with this reference, use polarity to identify reduction, then interpret more positive reduction potential as stronger oxidizing tendency.

Representative question

[Maximum number: 2]

Comment on the sign and value of the standard reduction potential of lithium that make it suitable to use in the battery. Use section 19 of the data booklet.

Retrieve the route: assign oxidation states, balance half-equations, predict displacement, label cells, trace electrons and ions, follow organic redox pathways, calculate potentials and choose electrolysis products.

Check electron loss/gain, anode/cathode versus polarity, spontaneous sign, salt-bridge direction, ions present, organic functional-group direction and object-cathode placement.

3.2.12 (HL)—Standard electrode potential (E⦵)

The Standard Hydrogen Electrode

Interpreting Standard Potentials

Assessment in practice

Electron Transfer Reactions Summary

Question 1