# Nernst Equation

(Difference between revisions)
 Revision as of 21:37, 14 November 2010 (view source)← Older edit Revision as of 21:38, 14 November 2010 (view source)Newer edit → Line 1: Line 1: − = Nernst Equation
= − '''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).
'''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).
Line 25: Line 23: R is the universal gas constant; R = 8.314471 J K-1 mol-1 R is the universal gas constant; R = 8.314471 J K-1 mol-1 − T is the thermodynamics temperature, in ''Kelvin''; 0 K = -273.15oC
+ T is the thermodynamics temperature, in ''Kelvin''; 0 K = -273.15oC
− z is the number of moles of electrons transferred between cells (defined by the valency of ions)
+ 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
+ F is the Faraday's constant; F = 96,485.3415 C mol-1
− [red] is the concentration of ion that gained electrons (reduction)
+ [red] is the concentration of ion that gained electrons (reduction)
− [oxi] is the concentration of ion that lost electrons (oxidation)
+ [oxi] is the concentration of ion that lost electrons (oxidation)

+
− == Membrane Potential
== + == 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:
+ 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:
+
+ [[Image:Nernst equation2.png|304x107px]] − [[Image:Nernst_equation2.png|304x107px]] +
+ or +
− or + [[Image:Nernst equation3.png|439x115px]] − + − + − + − [[Image:Nernst_equation3.png|439x115px]] + − + +
where where

## 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

Ecell is the half-cell potential difference

Eθcell 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 = -273.15oC

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