Set up an electrochemical cell consisting of Mg|MgSO4(1M) asone electrode by dipping a magnesium wire in 1 M MgSO4 solution andstandard hydrogen electrode Pt, H2 (1 atm)|H‌+(1 M) as the second electrode.Measure the EMF of the cell andalso note the direction of deflection in thevoltmeter. The direction of deflection shows that the electrons flow frommagnesium electrode to hydrogen electrode, i.e., oxidation takes place onmagnesium electrode and reduction on hydrogen electrode.Thus, the cell may be represented as follows :
E°cell=E° H+∕H2−E°Mg2+∕Mg
Put E° H+∕H2=0
Hence E°Mg2+∕Mg=−E°cell
It is observed that EMF of the cell comes out to be 2.36 V.
Hence standard electrode potential for Mg‌2+|Mg system will be E°=–2.36V.