How this calculation works
Enter E° and electron count for the same balanced reaction as written. Supply log₁₀(Q) directly or build its natural logarithm from positive dimensionless species activities and signed stoichiometric coefficients.
E = E° − (R T / (n F)) ln(Q); ln(Q) = sum(signed stoichiometric coefficient × ln(activity))A worked example
At 298.15 K, E° 1.1 V, n 2 and log₁₀(Q) 2, the Nernst correction is about 0.059159 V. The resulting ideal cell potential is about 1.040841 V.
Good to know
Educational equilibrium-activity model, not electrode design or safety guidance. No activity-coefficient solving, kinetics, resistance, junction potential, overpotential or automatic battery SOC inference.
Reference: OpenStax: Nernst equation and reaction potential (opens in a new tab) ↗
Keep the reaction direction consistent
The standard potential, electron transfer count and reaction quotient must all refer to the same balanced reaction. Reversing a reaction changes the potential sign and inverts its quotient.
A positive coefficient marks a product activity in the numerator; a negative coefficient marks a reactant contribution in the denominator. Coefficients are exponents, not amounts in moles.
The gas mixture partial pressure calculator adds compute ideal dry-gas mole fractions and partial pressures from component moles or masses, then add an independently entered vapor-pressure component. The arrhenius two temperature rate calculator adds predict a rate constant or infer apparent activation energy from two absolute temperatures, with explicit unit conventions and logarithmic calculations. The buffer ph ratio after strong addition calculator adds neutralize an entered strong addition against a weak conjugate pair, then estimate buffer pH only while both members remain present.
Activities are dimensionless
A raw concentration in mol/L or pressure in kPa is not automatically a thermodynamic activity. The relevant standard state and, when needed, activity coefficient determine that conversion.
Pure solids and pure liquids normally contribute unit activity and are omitted. The calculator cannot infer those phase conventions from an arbitrary species label.
Logarithmic input supports wide quotients
Direct log₁₀(Q) input avoids constructing extremely large or tiny quotients. Activity mode also sums logarithms rather than multiplying many factors and risking an avoidable overflow.
The Nernst correction is subtracted from the entered standard potential. A negative correction therefore raises E; neither the sign nor the resulting potential is silently replaced with an absolute value.
Use the result with the next measurement
The gas mixture partial pressure calculator can produce ideal component pressures. Convert those pressures to appropriate dimensionless activities before using them in this reaction quotient.
Educational equilibrium-activity model, not electrode design or safety guidance. No activity-coefficient solving, kinetics, resistance, junction potential, overpotential or automatic battery SOC inference.
A few questions, answered
Are species coefficients signed exponents?
Yes, positive for products and negative for reactants.
Can I use concentration as activity without a convention?
No, activities are dimensionless and require an appropriate basis.
Does this estimate real loaded voltage?
No, kinetic and resistance effects are excluded.