🔋 Nernst Equation Calculator
Find a cell’s actual potential from the standard potential, electrons transferred and reaction quotient, the Nernst equation at 25 °C.
Cell potential E
1.1592 V
Nernst equation at 25 °C: E = E° − (0.0592/n)·log₁₀(Q). n = electrons transferred, Q = reaction quotient. 🔒 Computed in your browser.
How the nernst equation calculator works
At 25 °C the Nernst equation is E = E° − (0.0592/n)·log₁₀(Q), where E° is the standard cell potential, n the number of electrons transferred, and Q the reaction quotient. Enter any three of E, E°, n, Q and the tool solves for the fourth. Rearranged, E° = E + (0.0592/n)·log Q, and Q can be solved from a measured potential; every tenfold change in Q shifts the potential by 0.0592/n volts.
Uses the 25 °C convention (0.0592 = 2.303RT/F at 298 K). As Q changes, the potential shifts away from E°; at equilibrium Q = K and E = 0 (a dead battery).
Frequently asked questions
What is the Nernst equation?
E = E° − (RT/nF)·ln Q, which at 25 °C simplifies to E = E° − (0.0592/n)·log₁₀ Q. It gives a cell’s potential under non-standard concentrations.
How do I calculate cell potential with concentrations?
Compute the reaction quotient Q from the concentrations, then apply E = E° − (0.0592/n)·log Q. Enter E°, n and Q and the tool returns E.
What is n in the Nernst equation?
The number of moles of electrons transferred in the balanced redox reaction. For Cu²⁺ + Zn → Cu + Zn²⁺, n = 2.
Why 0.0592?
It is 2.303·RT/F evaluated at 298 K (25 °C): 2.303 × 8.314 × 298 / 96485 ≈ 0.0592 V. At other temperatures the coefficient changes.
What happens at equilibrium?
Q equals the equilibrium constant K and E = 0, the cell can do no more work (it’s discharged).
A cell has E° = 1.10 V, n = 2, Q = 10, what is E?
E = 1.10 − (0.0592/2)·log 10 = 1.10 − 0.0296 × 1 = 1.07 V. Raising Q (more product) lowers the cell potential.
How does the Nernst equation give the equilibrium constant?
At equilibrium E = 0 and Q = K, so 0 = E° − (0.0592/n)·log K, giving log K = nE°/0.0592. A larger standard potential means a much larger K.
How does concentration change a cell’s voltage?
Through Q: raising product-ion concentration or lowering reactant-ion concentration increases Q and lowers E, while the reverse raises E. This is how concentration cells generate a voltage from the same electrode material at two different concentrations.
Why is the Nernst equation important for pH and ion-selective electrodes?
A pH meter is an electrochemical cell whose voltage depends on [H⁺] through the Nernst relation. Each pH unit (a tenfold change in [H⁺]) shifts the electrode potential by about 0.0592 V, which the meter converts back to pH.