Does Le Chatelier's principle apply to electrochemical cells?

1 Answer

Le Chatelier's Principle is very important when applied to electrochemical cells.

Consider the Daniel Cell:

The 2 half cells are:

Zn2++2eZn Eo=0.76V

Cu2++2eCu E0=+0.34V

To find E0cell you subtract the least positive value from the most positive value:

E0cell=+0.34(0.76)=+1.1V

And the cell reaction is therefore:

Zn+Cu2+Zn2++Cu

These refer to standard conditions i.e unit concentrations, 298K and pH zero.

What would happen if we were to reduce the concentration of Cu2+(aq) from 1mol/l to 0.1mol/l ?

Looking at the Cu2+/Cu half - cell Le Chatelier's Principle would predict that would cause the position of equilibrium to shift to the left to produce more Cu2+.

This would cause the E0 value to become less positive. This would therefore reduce the potential difference between the 2 half - cells and therefore the value of Ecell.

We can calculate the new value using the Nernst Equation which in this case is:

Ecell=E0cell0.05912log([Zn2+][Cu2+])

Ecell=1.10.05912×1

Ecell=+1.07V

So as predicted by Le Chatelier,. the value of Ecell has been reduced.