Electrochemistry II

How do we measure the the standard electrode potential?

Metals in contact with their ions in aqueous solutions
For example, we want to measure the standard electrode potential of Cu2+(aq)/Cu(s) half cell. The Cu2+(aq) /Cu(s) half cell consists of a copper electrode immersed in a 1M solution of Cu2+.

Ions of the same element in different oxidation state
For example, we want to measure the standard electrode potential of the Fe3+(aq)/Fe2+(aq) half cell. This half cell will consist of a platinum electrode immersed in a solution containing 1M Fe3+ and 1M Fe2+ ions

How to calculate standard cell potential by using standard electrode potential values in the data booklet?

For example if we want to calculate the standard cell potential for the following redox reaction:


We would look up the values for the standard half cell reactions from the data booklet.

Note that the standard electrode potential are always given as reduction potential. In our redox reaction Zn is oxidized, hence we have to reverse the sign of its standard electrode potential. Hence the standard cell potential would be +0.76 + (+0.34) = +1.10V

The standard cell potential is a positive value, indicating that the redox reaction is feasible.