What is the Nernst equation?

1 Answer
Feb 6, 2016

Answer:

#E_(cell)=E_(cell)^@-(RT)/(nF)lnQ#

Explanation:

The Nernst Equation is used to determine the cell potential #E_(cell)# of a galvanic cell. It is given by:

#E_(cell)=E_(cell)^@-(RT)/(nF)lnQ#

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=8.3145J/(mol*K)# is the universal gas constant ,

and #F=96485C/("mol "e^-)# is Faraday's constant .

For example, consider the following cell at #25^@C#, where the reaction is:

#2Al(s) + 3Mn^(2+)(aq) -> 2Al^(3+)(aq) + 3Mn(s)#

#[Mn^(2+)] = 0.50 M# and #[Al^(3+)] = 1.50 M#.

#Q=([Al^(3+)]^2)/([Mn^(2+)]^3)#

and #n=6# in this case.

#E_(cell)^@=0.48V#

#E_(cell)=0.48-(8.3145xx298)/(6xx96485)ln(((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.