Electrochemistry Calculator — Cell Potential, Nernst Equation, and ΔG

Electrochemistry sits at the intersection of thermodynamics and redox chemistry. Whether you're analyzing a galvanic cell, predicting whether a reaction will proceed spontaneously, or correcting for non-standard concentrations, the math involves a handful of related equations that the CalcHub Electrochemistry Calculator handles in one place.

Standard Cell Potential

For any galvanic (voltaic) cell:

E°cell = E°cathode − E°anode

Standard reduction potentials are measured relative to the standard hydrogen electrode (SHE = 0.00 V). The cathode is where reduction happens (higher E°); the anode is where oxidation happens (lower E°).

Example: Zn-Cu cell (classic Daniell cell)

• E°(Cu²⁺/Cu) = +0.34 V (cathode)
• E°(Zn²⁺/Zn) = −0.76 V (anode)
• E°cell = 0.34 − (−0.76) = +1.10 V

A positive E°cell means the reaction proceeds spontaneously. Negative means it's non-spontaneous.

The Nernst Equation

Standard potentials apply at 25°C with all concentrations at 1 M. Real conditions differ. The Nernst equation corrects for this:

E = E° − (RT/nF) × ln(Q)

At 25°C, this simplifies to:

E = E° − (0.0592/n) × log(Q)

Where:

• n = number of electrons transferred


• Q = reaction quotient (like Keq, but using actual concentrations)


• F = Faraday's constant (96,485 C/mol)

Relationship to Gibbs Free Energy

ΔG° = −nFE°cell

ΔG = −nFE (non-standard)

E°cell	ΔG°	Spontaneous?
Positive	Negative	Yes
Zero	Zero	At equilibrium
Negative	Positive	No (needs energy input)

How to Use the Calculator

1. Open CalcHub and select the Electrochemistry Calculator.
2. For standard calculations: enter the two half-cell reduction potentials.
3. For Nernst calculations: also enter n, temperature, and the reaction quotient Q.
4. For ΔG conversion: enter n and E°cell.

The tool handles all three modes and shows the connecting equations.

Common Reduction Potentials

Half-Reaction	E° (V)
F₂ + 2e⁻ → 2F⁻	+2.87
MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O	+1.51
O₂ + 4H⁺ + 4e⁻ → 2H₂O	+1.23
Cu²⁺ + 2e⁻ → Cu	+0.34
2H⁺ + 2e⁻ → H₂	0.00 (reference)
Zn²⁺ + 2e⁻ → Zn	−0.76
Li⁺ + e⁻ → Li	−3.04

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How does the Nernst equation affect cell potential as a reaction proceeds?

As reactants are consumed and products accumulate, Q increases. The term (0.0592/n)×log(Q) grows, reducing E. When E = 0, Q = Keq and the cell is at equilibrium — this is a dead battery.

What's the difference between a galvanic cell and an electrolytic cell?

A galvanic cell uses a spontaneous reaction to generate electricity (positive E°cell). An electrolytic cell uses external electricity to drive a non-spontaneous reaction (negative E°cell) — like electroplating or the electrolysis of water. The math is the same; the sign and energy direction differ.

Can I use this to predict whether a metal will corrode?

Yes. Corrosion is an electrochemical process. If the cell potential for the metal oxidizing in the presence of water/oxygen is positive, corrosion is thermodynamically favored. Many common corrosion reactions can be analyzed this way.

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