# Nernst Equation

(Difference between revisions)
 Revision as of 21:30, 14 November 2010 (view source) (Created page with '= Nernst Equation
= '''Nernst Equation''' is an equation used to calculate the electrical potential of a chemical reaction. In its equilibrium state, the Nernst equation sh…') Revision as of 21:37, 14 November 2010 (view source)Newer edit → Line 23: Line 23: 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; 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:
+ + + + [[Image:Nernst_equation2.png|304x107px]] + + + + or + + + + [[Image:Nernst_equation3.png|439x115px]] + + + + where

# 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).

## 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