Electrochemical Cell Potential Calculator

An electrochemical cell generates voltage by coupling two half-reactions: an oxidation at the anode and a reduction at the cathode. The total cell potential is the difference between their standard reduction potentials.

E°cell = E°cathode - E°anode

Standard reduction potentials are measured relative to the standard hydrogen electrode (SHE), defined as 0.000 V. A positive E°cell means the reaction is spontaneous under standard conditions (1 M concentrations, 1 atm, 25°C).

Some common standard reduction potentials (E° vs SHE):

• Zn²⁺ + 2e⁻ → Zn: -0.76 V (commonly the anode in zinc-based cells)
• Fe²⁺ + 2e⁻ → Fe: -0.44 V
• 2H⁺ + 2e⁻ → H₂: 0.00 V (reference electrode)
• Cu²⁺ + 2e⁻ → Cu: +0.34 V
• Ag⁺ + e⁻ → Ag: +0.80 V
• Cl₂ + 2e⁻ → 2Cl⁻: +1.36 V

A classic zinc-copper Daniell cell: E°cell = 0.34 - (-0.76) = 1.10 V

The relationship to Gibbs free energy:

ΔG° = -n × F × E°cell

Where n = moles of electrons transferred and F = Faraday’s constant (96,485 C/mol). A negative ΔG° confirms the reaction is thermodynamically favorable.

The equilibrium constant Keq can also be found: log(Keq) = n × E°cell / 0.05916 (at 25°C).

Note: the Nernst equation adjusts E°cell for non-standard concentrations. E = E° - (RT/nF) × ln(Q), which at 25°C simplifies to E = E° - (0.05916/n) × log(Q).