Calculate standard electrode potential and cell potential using the Nernst equation for electrochemical half-cells and full reactions
Cell Potential (E)
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Nernst Term (RT/nF × ln(Q))
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Temperature
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Reference Electrode Correction
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Standard electrode potential (E°) is the voltage of an electrochemical cell when all components are at standard conditions (25°C, 1 atm pressure, 1M concentration). It measures the tendency of a species to be reduced.
The Nernst equation calculates the electrode potential under non-standard conditions: E = E° - (RT/nF) × ln(Q). It accounts for temperature and concentration effects on cell potential.
The reaction quotient Q is the ratio of product activities to reactant activities. For aA + ne⁻ → bB, Q = [B]ᵇ/[A]ᵃ. Use concentrations for dilute solutions and activities for precise calculations.
Temperature affects the kinetic energy of ions and the equilibrium position of redox reactions. Higher temperatures generally decrease cell potential due to the RT term in the Nernst equation.
NHE (Normal Hydrogen Electrode) and SHE (Standard Hydrogen Electrode) are both hydrogen-based references set at 0.000 V. SHE is the modern standard, while NHE is the older designation.
Use the number of electrons transferred in the balanced half-reaction. For example, Cu²⁺ + 2e⁻ → Cu uses n = 2, while Fe³⁺ + e⁻ → Fe²⁺ uses n = 1.
Yes, electrode potentials can be negative. Negative values indicate that the half-reaction is less favorable than the hydrogen reference. Many metals like zinc have negative standard potentials.