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Nernst Equation

Chemistry: Cambridge International A Level, topic 1.6.4

Nernst Equation

The Nernst equation can be used to calculate cell potentials under non-standard conditions. In particular, it is used when non-standard concentrations (not 1 mol dm-3) are used.

Non-standard conditions

Non-standard conditions

  • Standard conditions are a temperature of 298 K, a concentration of 1 mol dm-3, and a pressure of 1 atmosphere.
  • A deviation from any of these means conditions are non-standard.
  • In non-standard cells, the concentrations of the active species, therefore, impact the cell potential.
  • For your exam, you need to be able to calculate the cell potential when concentrations are non-standard.
Nernst equation

Nernst equation

  • The Nernst equation is shown below:
  • 𝐸cell = 𝐸ocell + (0.059/z) log [oxidized species][reduced species]\large \frac {[oxidized\ species]}{[reduced\ species]}
  • 𝐸cell is the cell potential under the new conditions.
  • 𝐸ocell is the standard cell potential.
  • 0.059 is a temperature and pressure constant.
  • z is the number electrons are transferred.
Interpreting Nernst equation

Interpreting Nernst equation

  • The equation describes how the potential of a redox system (such as a galvanic cell) varies from its standard state value.
  • Specifically, it shows how the potential of a redox system is a function of the number of electrons transferred, zz.

Test yourself on Nernst Equation

  • What is the Nernst equation?

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