Standard electrode potentials E°, standard cell potentials Ecell and the Nernst equation

Need to know

What you need to know

• **Standard Conditions:** 298 K (25 °C), 1.00 mol dm⁻³ concentration of all aqueous ions, and 1 atm pressure for all gases.
• **Reference:** The Standard Hydrogen Electrode (SHE): 2H⁺(aq) + 2e⁻ ⇌ H₂(g), E° = 0.00 V.
• **Interpretation:** A more positive E° means the species on the left of the half-equation is a strong oxidising agent. A more negative E° means the species on the right is a strong reducing agent.

Explanation

Electrochemical Tug-of-War

1. E° measures tendency to reduce — higher E° = stronger oxidising agent.
2. E°cell = E°(cathode) − E°(anode) for a spontaneous cell.
3. ΔG° = −nFE°cell — link thermodynamics to electrochemistry.
4. Nernst: E = E° − (RT/nF) ln Q — non-standard concentrations.