Nernst’s Equation for Cell EMF

For a cell in which the net cell reaction involving n electrons is, 

The Nernst equation is written as,

Where, .

The  is called the standard cell potential.

or 

At 298 K, above eq. can be written as,

or 

It may be noted here, that the concentrations of A, B, C and D referred in the eqs. are the concentrations at the time the cell emf is measured.