Nernst Equation (Cell Potential vs Concentration)
The electrochemistry member the lab chemistry set (ideal gas, Arrhenius) was missing.
Example
You enter
- Standard potential E0 (V) 1.1
- Electrons transferred n 2
- Reaction quotient Q 0.01
- Temperature (°C) 25
You get
- Cell / electrode potential E 1.1592 V
- Nernst slope (per decade of Q) 29.58 mV/decade
Checked against published worked examples from: Nernst (standard-state cross-check).
Details, formula, and sources
ScopeCorrects a standard potential for the actual mix of species: E = E0 - (RT/nF) ln Q, R = 8.314 J/(mol*K), F = 96485 C/mol, T in kelvin. At 25 C each tenfold change in the reaction quotient Q shifts the potential by 0.05916/n V, so a one-electron pH electrode reads 59 mV per pH unit. When Q = 1 the potential equals E0. Reports the cell potential and the Nernst slope per decade. Uses concentrations for activities and ignores junction potential and overpotential. A first-principles chemistry aid.
Formula or tableE = E0 - (RT/nF) ln Q; R = 8.314 J/(mol*K), F = 96485 C/mol, T in kelvin. At 25 C the slope is 0.05916/n V per decade of Q. Nernst slope = RT ln(10)/(nF).
Source and editionThe Nernst equation (Nernst, 1889); standard electrochemistry. First principles.
Free accessThe Nernst equation and the constants R and F are public first-principles chemistry; the standard potential, electron count, and reaction quotient are the user's own inputs.
What governsVerify protocol against your lab's SOP before pipetting. A miscalculated dilution can ruin a run or a sample.
API field namesstandard_potential_v, electrons_n, reaction_quotient, temperature_c, cell_potential_v, nernst_slope_v
- Nernst equation E = E0 - (RT/nF) ln Q; R = 8.314, F = 96485, T in kelvinNernst (1889)
- 25 C slope 0.05916/n V per decade of Q (59 mV/pH for n = 1)RT ln(10)/F at 298.15 K
- Scope activities approximated by concentrations; excludes junction potential and overpotentialscope of this tile