Cell EMF Calculator
Determine standard and non-standard cell potentials from half-reaction data, temperature, and reaction conditions.
Use Q = 1 for standard-state conditions.
Standard EMF
1.56 V
Adjusted EMF
1.56 V
Nernst adjustment
0 V
How to Use This Calculator
Collect half-reaction data
Look up standard reduction potentials for the cathode and anode from electrochemical tables.
Enter stoichiometry
Specify the number of electrons transferred in the balanced overall reaction.
Provide reaction conditions
Set the reaction quotient and temperature to evaluate non-standard conditions.
Review the EMF results
Compare the standard EMF with the Nernst-adjusted value to gauge driving force.
Formula
Ecell0 = Ecathode0 - Eanode0
Ecell = Ecell0 - (RT / nF) ln(Q)
Use R = 8.314 J/(mol K), F = 96485 C/mol, temperature in Kelvin, electrons n, and reaction quotient Q based on activities or concentrations.
Example
With Ecathode0 = 0.80 V, Eanode0 = -0.76 V, n = 2, Q = 0.010, and T = 298 K: E0 = 1.56 V and E = 1.56 - (0.0257/2) ln(0.010) is about 1.60 V.
Full Description
Electrochemical cells produce electrical work from redox reactions. The electromotive force depends on the intrinsic driving force between cathode and anode plus any deviation from standard conditions.
This calculator combines tabulated half-cell potentials with the Nernst equation so you can quickly estimate operating voltages for galvanic or electrolytic setups.
Frequently Asked Questions
Why subtract anode potential?
Anode potentials are oxidation potentials. Convert to reduction form or subtract the reduction values to find the cell EMF.
What if I only need the standard voltage?
Leave Q at 1 and temperature at 298 K. The calculator will report only the standard EMF.
Can Q include gases?
Yes. Use partial pressures (atm) for gaseous species and concentrations for solutes to form the reaction quotient.
How accurate is the Nernst equation?
It works well for dilute solutions and ideal behavior. Activities or activity coefficients improve precision for concentrated systems.
Does temperature affect the standard potentials?
Standard tables are typically reported at 298 K. Temperature changes alter both the Nernst correction and the underlying potentials slightly.