24.2.9—Nernst equation

At 25 °C, E = E° + (0.059/z) log([oxidised]/[reduced]) for the stated reduction half-equation. z is the number of electrons transferred.

Use activities/concentrations only for aqueous species in the simplified syllabus form, keep the ratio in the correct direction, and use base-10 logarithms.

For Fe³⁺ + e⁻ ⇌ Fe²⁺, increasing [Fe³⁺]/[Fe²⁺] makes E more positive. For Cu²⁺/Cu, the solid copper is omitted from the ratio.

Do not use z from the overall cell equation if the half-equation transfers a different number of electrons, and do not include pure solids.