Question

How would you determine the standard electrode potential of the system Mg²⁺ | Mg? 

Answer 1

The standard electrode potential of Mg²⁺ | Mg can be measured with respect to the standard hydrogen electrode, represented by 

Pt_(s), H_2(g) (1 atm) | H⁺_(aq)(1 M).
A cell, consisting of Mg | MgSO₄ (aq 1 M) as the anode and the standard hydrogen electrode as the cathode, is set up.

Then, the emf of the cell is measured and this measured emf is the standard electrode potential of the magnesium electrode.

E^ø  = E^ø_R  - E^ø_L

Here,E^øR for the standard hydrogen electrode is zero.

∴ E^ø = 0 - E^ø_L

₌ - E^ø_L