Nernst Equation Calculator
Calculate cell potential and reduction potential using the Nernst equation for electrochemical reactions
Calculate Cell Potential
Standard reduction potential under standard conditions
Temperature at which the reaction occurs
Number of moles of electrons transferred in the reaction
Activities can be approximated by concentrations (M)
Nernst Equation Results
Nernst Equation: E = E₀ - (RT/zF) × ln([red]/[ox])
Calculation: 0 - (8.314 × 298.1) / (1 × 96485.3) × ln(1.000)
Analysis: The reaction is at equilibrium under these conditions
Electrochemical Analysis
Example Calculation
Galvanic Cell Example
Reaction: Pb²⁺(aq) + Mg(s) → Mg²⁺(aq) + Pb(s)
Half-reactions:
• Mg → Mg²⁺ + 2e⁻ (E₀ = +2.38 V)
• Pb²⁺ + 2e⁻ → Pb (E₀ = -0.13 V)
Total E₀: 2.38 + (-0.13) = 2.25 V
Conditions: [Mg²⁺] = 0.020 M, [Pb²⁺] = 0.200 M, 25°C
Expected Result
E = 2.25 - (8.314 × 298.15)/(2 × 96,485.3) × ln(0.020/0.200)
E = 2.25 - 0.0128 × ln(0.1)
E ≈ 2.28 V (Spontaneous reaction)
Nernst Equation Components
Cell Potential
Actual potential (V)
Under given conditions
Standard Potential
Standard conditions (V)
25°C, 1 M, 1 bar
Electrons
Moles transferred
In the reaction
Physical Constants
R = 8.314 J/(K·mol)
F = 96,485.3 C/mol
Standard T = 298.15 K (25°C)
Standard P = 1 bar
Electrochemistry Tips
Positive E = spontaneous reaction (galvanic cell)
Negative E = non-spontaneous (electrolytic cell)
Higher [ox]/[red] ratio increases cell potential
Temperature affects cell potential via RT term
Understanding the Nernst Equation
What is the Nernst Equation?
The Nernst equation, developed by Walther Nernst in 1889, relates the cell potential of an electrochemical reaction to the standard electrode potential, temperature, and the activities (or concentrations) of the chemical species involved. It's fundamental to understanding electrochemistry and predicting reaction behavior.
Key Applications
- •Battery design and performance prediction
- •Corrosion studies and prevention
- •Electroplating and electrorefining
- •pH measurement and ion-selective electrodes
The Nernst Equation
E = E₀ - (RT/zF) × ln([red]/[ox])
- E: Cell potential under given conditions (V)
- E₀: Standard reduction potential (V)
- R: Gas constant (8.314 J/(K·mol))
- T: Temperature (K)
- z: Number of electrons transferred (mol)
- F: Faraday constant (96,485.3 C/mol)
- [red]/[ox]: Activity ratio (reduced/oxidized forms)
Note: At 25°C, RT/F = 0.0257 V, simplifying calculations for standard conditions.
Practical Significance
Energy Storage
Determines voltage and capacity of batteries, fuel cells, and other energy storage devices.
Industrial Processes
Essential for electroplating, metal refining, and chemical synthesis via electrolysis.
Analytical Chemistry
Basis for potentiometric measurements, pH meters, and ion-selective electrodes.