How would you determine the standard electrode potential of the system ${{Mg}^{2+}}$/Mg?



E° value of ${{Mg}^{2+}}$/Mg electrode is determined by setting up an electrochemical cell. For this purpose, a Mg electrode is dipped in 1 M $MgSO_{4}$ solution which acts as one half-cell, i.e. oxidation half-cell.

In the same way, the standard hydrogen electrode acts as the other half-cell, i.e. reduction half-cell. The deflection of voltmeter placed in the cell circuit is towards the Mg electrode which indicates the direction of flow of current. The cell may be represented as:
Mg | ${{Mg}^{2+}}$ (1 M) | ${{H}^{+}}$(1M)| $H_{2}$(l bar), Pt (s)
The reading as given by voltmeter, gives E° cell