# Nernst Equation

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'''Nernst Equation''' is an equation used to calculate the electrical potential of a chemical reaction. In its equilibrium state, the Nernst equation should be zero. It also shows the direct relation between energy or potential of a cell and its participating ions. The equation is proposed by a German chemist, Walther H. Nernst (1864-1941).<br> | '''Nernst Equation''' is an equation used to calculate the electrical potential of a chemical reaction. In its equilibrium state, the Nernst equation should be zero. It also shows the direct relation between energy or potential of a cell and its participating ions. The equation is proposed by a German chemist, Walther H. Nernst (1864-1941).<br> | ||

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R is the universal gas constant; R = 8.314471 J K<sup>-1</sup> mol<sup>-1</sup> | R is the universal gas constant; R = 8.314471 J K<sup>-1</sup> mol<sup>-1</sup> | ||

− | T is the thermodynamics temperature, in ''Kelvin''; 0 K = -273.15<sup>o</sup>C<br> | + | T is the thermodynamics temperature, in ''Kelvin''; 0 K = -273.15<sup>o</sup>C<br> |

− | z is the number of moles of electrons transferred between cells (defined by the valency of ions)<br> | + | z is the number of moles of electrons transferred between cells (defined by the valency of ions)<br> |

− | F is the Faraday's constant; F = 96,485.3415 C mol<sup>-1</sup><br> | + | F is the Faraday's constant; F = 96,485.3415 C mol<sup>-1</sup><br> |

− | [red] is the concentration of ion that gained electrons (reduction)<br> | + | [red] is the concentration of ion that gained electrons (reduction)<br> |

− | [oxi] is the concentration of ion that lost electrons (oxidation)<br> | + | [oxi] is the concentration of ion that lost electrons (oxidation)<br> |

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− | == Membrane Potential<br> == | + | == Membrane Potential<br> == |

− | Nernst equation is also can be used to calculate the potential of an ion across the membrane. For potential difference of a membrane, we can manipulate the Nernst Equation as follows:<br> | + | Nernst equation is also can be used to calculate the potential of an ion across the membrane. For potential difference of a membrane, we can manipulate the Nernst Equation as follows:<br> |

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+ | [[Image:Nernst equation2.png|304x107px]] | ||

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## Revision as of 21:38, 14 November 2010

**Nernst Equation** is an equation used to calculate the electrical potential of a chemical reaction. In its equilibrium state, the Nernst equation should be zero. It also shows the direct relation between energy or potential of a cell and its participating ions. The equation is proposed by a German chemist, Walther H. Nernst (1864-1941).

## Equation

Nernst equation can be expressed as follows:

where

E_{cell }is the half-cell potential difference

E^{θ}_{cell }is the standard half-cell potential

R is the universal gas constant; R = 8.314471 J K^{-1} mol^{-1}

T is the thermodynamics temperature, in *Kelvin*; 0 K = -273.15^{o}C

z is the number of moles of electrons transferred between cells (defined by the valency of ions)

F is the Faraday's constant; F = 96,485.3415 C mol^{-1}

[red] is the concentration of ion that gained electrons (reduction)

[oxi] is the concentration of ion that lost electrons (oxidation)

## Membrane Potential

Nernst equation is also can be used to calculate the potential of an ion across the membrane. For potential difference of a membrane, we can manipulate the Nernst Equation as follows:

or

where