Redox potential?

Question

If increasing the concentration of a reducing or oxidisng agent increases its 'reducing' or 'oxidising' power why does the redox potential plateau once you get to a very high concentration? Why does it not continue to get higher/lower with increasing concentration of the solution in question?

Answer 1

The reducing or oxidising power, like all the expressions related to free energy, depends on the log of the concentration.

A logarithm increases much more quickly at lower values that at higher values. For instance, the logarithm increases by the same amount when going from 0.01 to 0.1, from 0.1 to1,or from 1 to 10. So it does continue to change, but much more slowly.