The equilibrium constant for the reaction sr(s) + mg2+(aq) ⇌ sr2+(aq) + mg(s) is 3.69 × 1017 at 25°c. calculate e o for a cell made up of sr / sr2+ and mg / mg2+ half-cells.

We are going to use this formula:

E° = 0.0592/ n * ㏒K

when E° is the standard state cell potential

and n is number of moles of electrons transferred in the balanced equation

for the reaction of the cell.

Sr(s) + Mg2+ (aq) ↔ Sr2+(aq) + Mg(s)

we can get it by using the given balanced equation, we here have 2 electrons

transferred so, n = 2 

and K the equilibrium constant = 3.69 x 10^17

so, by substitution:

∴ E° = 0.0592 / 2 * ㏒ (3.69 x 10^17)

        = 0.52 V

Both models are effective because they show the valence electrons, and these valence electrons indicate the reactivity of an element.