# Electrochemical Cell Voltage Calculator

Free electrochemical cell calculator. Calculate E°_cell from half-cell potentials. Includes ΔG°, equilibrium constant, and spontaneity.

## What this calculates

Calculate the standard cell potential from half-cell reduction potentials: E°_cell = E°_cathode - E°_anode. Also calculates ΔG° and the equilibrium constant K.

## Inputs

- **Cathode Half-Cell** — options: Custom (enter value below), Cu²⁺/Cu: +0.340 V, Ag⁺/Ag: +0.799 V, Fe³⁺/Fe²⁺: +0.771 V, Cl₂/Cl⁻: +1.360 V, Au³⁺/Au: +1.500 V, O₂/H₂O (acidic): +1.229 V, H⁺/H₂ (SHE): 0.000 V, Sn²⁺/Sn: -0.136 V, Ni²⁺/Ni: -0.257 V — Select the cathode (reduction occurs here).
- **Anode Half-Cell** — options: Custom (enter value below), Zn²⁺/Zn: -0.763 V, Fe²⁺/Fe: -0.440 V, Pb²⁺/Pb: -0.126 V, Ni²⁺/Ni: -0.257 V, Sn²⁺/Sn: -0.136 V, H⁺/H₂ (SHE): 0.000 V, Cu²⁺/Cu: +0.340 V, Al³⁺/Al: -1.660 V, Mg²⁺/Mg: -2.372 V, Li⁺/Li: -3.040 V — Select the anode (oxidation occurs here).
- **Cathode E° (reduction)** (V) — Standard reduction potential of the cathode.
- **Anode E° (reduction)** (V) — Standard reduction potential of the anode.
- **Electrons Transferred (n)** — min 1, max 20 — Number of electrons transferred (for ΔG calculation).

## Outputs

- **Standard Cell Potential (E°_cell)** (V) — E°_cell = E°_cathode - E°_anode.
- **Spontaneity** — formatted as text — Whether the cell reaction is spontaneous.
- **ΔG°** (kJ/mol) — Standard Gibbs free energy: ΔG° = -nFE°.
- **Equilibrium Constant (log K)** — formatted as text — log K = nFE° / (2.303RT) at 25°C.
- **Calculation** — formatted as text — Step-by-step calculation.

## Frequently Asked Questions

**Q: How do I calculate E°_cell?**

A: E°_cell = E°_cathode - E°_anode. Use the standard reduction potentials for both half-cells. The cathode is where reduction occurs, and the anode is where oxidation occurs. A positive E°_cell means the reaction is spontaneous.

**Q: What is the standard hydrogen electrode?**

A: The SHE (Standard Hydrogen Electrode) is the reference electrode with E° = 0.000 V. All other standard reduction potentials are measured relative to the SHE. The half-reaction is 2H⁺ + 2e⁻ → H₂.

**Q: What is the difference between galvanic and electrolytic cells?**

A: A galvanic (voltaic) cell has a positive E°_cell and spontaneously generates electricity. An electrolytic cell has a negative E°_cell and requires external electricity to drive the non-spontaneous reaction.

**Q: Do I flip the sign of E° for the anode?**

A: No. Always use standard reduction potentials from the table as-is. The formula E°_cell = E°_cathode - E°_anode already accounts for the anode undergoing oxidation (the reverse of reduction).

---

Source: https://vastcalc.com/calculators/chemistry/electrochemical-cell
Category: Chemistry
Last updated: 2026-04-21