Balance electron transfer in a redox reaction and calculate the cell potential.
A positive cell potential means a spontaneous reaction, and the free energy change scales with both potential and electron count. Electron numbers must be equalised between half-reactions before combining, though this does not change the potential. Cell potential is intensive and does not depend on how the equation is scaled, whereas free energy does — a distinction that catches out many students.
Redox Reaction
E°cell = E°oxidation + E°reduction; ΔG° = −nFE°cell
E°cell = E°oxidation + E°reduction; ΔG° = −nFE°cell A positive cell potential means a spontaneous reaction, and the free energy change scales with both potential and electron count. Electron numbers must be equalised between half-reactions before combining, though this does not change the potential.
Cell potential is intensive and does not depend on how the equation is scaled, whereas free energy does — a distinction that catches out many students.
This calculator takes 4 inputs: Standard potential of the oxidation half-reaction, Standard potential of the reduction half-reaction, Electrons in the oxidation half-reaction, Electrons in the reduction half-reaction. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.