Chemistry class 12th Nernst equation explanation

Nernst Equation - Full Explanation



Nernst Equation - Full Explanation


Introduction:
The Nernst equation is a mathematical expression that relates the electrode potential of an
electrochemical cell
to the concentration of ions involved in the reaction. It helps in determining the cell potential under
non-standard conditions.


Nernst Equation:
The general form of the Nernst equation is:


E = E° - (RT/nF) * ln(Q)


Where:
- E = Electrode potential (V)
- E° = Standard electrode potential (V)
- R = Universal gas constant (8.314 J/mol·K)
- T = Temperature in Kelvin (K)
- n = Number of electrons transferred
- F = Faraday's constant (96485 C/mol)
- Q = Reaction quotient (ratio of product and reactant concentrations)


At standard temperature (25°C or 298K), the equation simplifies to:


E = E° - (0.0591/n) * log(Q)


Derivation of the Nernst Equation:
The Nernst equation is derived from the Gibbs free energy equation:


G = G° + RT ln(Q)


Since G = -nFE and G° = -nFE°, we substitute these values:


-nFE = -nFE° + RT ln(Q)