# Nernst Equation

(Difference between revisions)
 Revision as of 21:59, 14 November 2010 (view source)Nnjm2 (Talk | contribs)← Older edit Revision as of 22:02, 14 November 2010 (view source)Nnjm2 (Talk | contribs) Newer edit → Line 1: Line 1: − '''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 [[Ion|ions]]. The equation is proposed by a German chemist, Walther H. Nernst (1864-1941).
== Equation  == == Equation  == Line 13: Line 13: Eθcell is the standard half-cell potential Eθcell is the standard half-cell potential − R is the universal gas constant; R = 8.314471 J K-1 mol-1 + R is the [[Universal gas constant|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|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|moles]] of [[Electrons|electrons]] transferred between cells (defined by the valency of [[Ion|ions]])
− F is the Faraday's constant; F = 96,485.3415 C mol-1
+ F is the [[Faraday's constant|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|ion]] that gained [[Electrons|electrons]] ([[Reduction|reduction]])
− [oxi] is the concentration of ion that lost electrons (oxidation)
+ [oxi] is the concentration of [[Ion|ion]] that lost [[Electrons|electrons]] ([[Oxidation|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|ion]] across the membrane. For potential difference of a membrane, we can manipulate the Nernst Equation as follows:
[[Image:Nernst equation2.png|278x98px]]
[[Image:Nernst equation2.png|278x98px]]

## Revision as of 22:02, 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

Em is the potential difference of an ion between membranes

R is the universal gas constant; R = 8.314471 J mol-1

T is the thermodynamics temperature, in Kelvin; 0 K = -273.15oC

z is the number of moles of electrons transferred between membranes (defined by the valency of ion)

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

[A-1] is the concentration of ion outside the membrane

[A-1] is the concentration of ion inside the membrane

## Application

### Using Study of Frog Skin

In biochemistry, Nernst equation can be used to calculate the potential difference of ion between membranes. Hans H. Ussing, a Danish scientist, used a frog skin to measure the potential difference of sodium and potassium ions across the membranes with his famous invention, the Ussing chamber.