Nernst Equation Calculator Formula

Understand the math behind the nernst equation calculator. Each variable explained with a worked example.

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Formulas Used

Cell Potential (E)

e_cell = e_standard - ((8.314 * temp) / (n_electrons * 96485)) * log(q)

Variables

VariableDescriptionDefault
e_standardStandard Cell Potential (E°)(V)1.1
n_electronsElectrons Transferred (n)2
tempTemperature (T)(K)298
qReaction Quotient (Q)0.01

How It Works

Nernst Equation

Formula

E = E° − (RT / nF) × ln(Q)

Where:

  • E = cell potential under non-standard conditions (V)
  • E° = standard cell potential (V)
  • R = 8.314 J/(mol·K)
  • T = temperature (K)
  • n = number of electrons transferred
  • F = 96485 C/mol (Faraday constant)
  • Q = reaction quotient

    • At 25°C this simplifies to: E = E° − (0.0592/n) × log₁₀(Q)

    Worked Example

    Cu/Zn cell with E° = 1.10 V, n = 2, T = 298 K, Q = 0.01.

    e_standard = 1.1n_electrons = 2temp = 298q = 0.01
    1. 01E = E° - (RT/nF) × ln(Q)
    2. 02E = 1.10 - (8.314×298)/(2×96485) × ln(0.01)
    3. 03E = 1.10 - (0.01285) × (-4.605)
    4. 04E = 1.10 + 0.0592
    5. 05E = 1.159 V

    Frequently Asked Questions

    When is the Nernst equation needed?

    Use it when concentrations are not 1 M (non-standard conditions). The standard cell potential assumes all concentrations are 1 M.

    What happens when Q = 1?

    When Q = 1, ln(Q) = 0, so E = E°. Standard conditions correspond to Q = 1.

    What happens at equilibrium?

    At equilibrium, E = 0 and Q = K. The Nernst equation gives: 0 = E° - (RT/nF)ln(K), which relates E° to K.

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