The Nernst Equation is used to determine the cell potential Ecell of a galvanic cell. It is given by:
Ecell=E∘cell−RTnFlnQ
Where, E∘cell is the cell potential at standard conditions,
Q is the reaction quotient ,
n is the number of electrons exchanged between the cathode and the anode,
R=8.3145Jmol⋅K is the universal gas constant ,
and F=96485Cmol e− is Faraday's constant .
For example, consider the following cell at 25∘C, where the reaction is:
2Al(s)+3Mn2+(aq)→2Al3+(aq)+3Mn(s)
[Mn2+]=0.50M and [Al3+]=1.50M.
Q=[Al3+]2[Mn2+]3
and n=6 in this case.
E∘cell=0.48V
Ecell=0.48−8.3145×2986×96485ln((1.50)2(0.50)3)=0.47V
Here is a video that explains in details the Nernst Equation and its uses:
Electrochemistry | The Concentration Cell.