Electrochemistry Calculator
Calculate standard cell potential, Gibbs free energy, the equilibrium constant and the Nernst equation for galvanic cells, with each step shown.
What this calculator does
Work out E°cell from the half-cell potentials, convert it to ΔG° and K, or apply the Nernst equation to non-standard conditions.
When you need it
Cell potentials predict whether a redox reaction is spontaneous and how much voltage a battery gives. The same equations describe corrosion, electroplating and fuel cells.
Formulas
- E°cell = E°cathode − E°anode
- ΔG° = −nFE°
- F = 96 485 C/mol
- E = E° − (RT ÷ nF) ln Q
How to use it
- Choose the calculation: cell potential, ΔG°, K or Nernst.
- Enter the potentials, the number of electrons n and, for Nernst, Q and the temperature.
- Read the result and whether the cell is spontaneous.
Worked example
A zinc-copper cell has E°(Cu²⁺/Cu) = +0.34 V and E°(Zn²⁺/Zn) = −0.76 V. Find E°cell and ΔG°.
- E°cell = 0.34 − (−0.76) = 1.10 V
- n = 2 electrons
- ΔG° = −nFE° = −2 × 96 485 × 1.10 = −212 267 J
Answer
E°cell = 1.10 V and ΔG° = −212 kJ/mol, so the cell is spontaneous.
Common mistakes
- Flipping the sign of the anode potential twice.
- Multiplying E° by the coefficients: potentials are not scaled by the balanced equation.
- Using J and kJ in the same step.
Related tools
Frequently asked questions
What is a standard cell potential?
The voltage of a galvanic cell with all species at standard conditions. A positive E°cell means the cell reaction is spontaneous.
What is the Nernst equation?
It corrects the cell potential for concentrations that are not standard: E = E° − (RT ÷ nF) ln Q.
How are E° and K related?
ΔG° = −nFE° = −RT ln K, so a positive E° means K is greater than 1.