Standard Electrode Potential Calculator
Calculate the standard cell potential (E°cell) from cathode and anode half-reaction potentials. Also determines the standard Gibbs free energy change (ΔG°), whether the reaction is spontaneous, and the equilibrium constant (Keq).
Electrochemical cells convert chemical energy to electrical energy (galvanic cells) or vice versa (electrolytic cells). The standard cell potential determines the voltage a cell can produce under standard conditions.
Key Equations:
- E°cell = E°(cathode) - E°(anode): The cell potential is the difference between the reduction potentials of the two half-reactions. The cathode is where reduction occurs; the anode is where oxidation occurs.
- ΔG° = -nFE°cell: Links cell potential to thermodynamics. F = 96,485 C/mol (Faraday constant), n = electrons transferred. A positive E°cell gives a negative ΔG° (spontaneous).
- Keq = e^(nFE°/RT): Links cell potential to the equilibrium constant. Even small positive E°cell values correspond to very large Keq values.
Example: Daniell Cell (Zn-Cu):
Cathode: Cu²⁺ + 2e⁻ → Cu (E° = +0.34 V). Anode: Zn²⁺ + 2e⁻ → Zn (E° = -0.76 V). E°cell = 0.34 - (-0.76) = 1.10 V. ΔG° = -2(96485)(1.10)/1000 = -212.3 kJ/mol. The large positive E°cell and very large Keq confirm this reaction strongly favors products.