What is the Nernst equation?

1 Answer
Feb 6, 2016

Ecell=EcellRTnFlnQ

Explanation:

The Nernst Equation is used to determine the cell potential Ecell of a galvanic cell. It is given by:

Ecell=EcellRTnFlnQ

Where, Ecell 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=8.3145JmolK is the universal gas constant ,

and F=96485Cmol e is Faraday's constant .

For example, consider the following cell at 25C, 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.

Ecell=0.48V

Ecell=0.488.3145×2986×96485ln((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.