Skip to main content

Cell Potential Under Nonstandard Conditions

Electrochemical cell potentials are often measured under standard conditions, but in real-world scenarios, concentrations and pressures vary. The Nernst equation allows us to calculate cell potential under nonstandard conditions.

Nernst Equation​

  • Equation:
    E = E⁰ − (0.0592 / n) log Q (at 25°C)
    Where:

    • E⁰ = standard cell potential
    • n = number of electrons transferred
    • Q = reaction quotient = [products]^coefficients / [reactants]^coefficients

  • Significance:

    • Adjusts the cell potential for non-1 M concentrations or non-1 atm pressures.
    • Shows how Ecell changes as a reaction progresses.

Reaction Quotient (Q)​

  • Calculated using concentrations of reactants and products:
    • Q = [C]^c [D]^d / [A]^a [B]^b
    • Example: For a reaction aA + bB → cC + dD
  • As Q changes, the cell potential decreases until equilibrium is reached (Ecell = 0).

Key Points​

  • Ecell decreases as the reaction approaches equilibrium.
  • At equilibrium:
    • Q = K
    • Ecell = 0
    • ΔG = 0
  • Nonstandard conditions are common in real-world electrochemical applications, so the Nernst equation is essential for accurate predictions.

Have Questions?​

If you have any questions, or are looking for more resources, you can join our Discord Server