Question

Give reasons :

E° value for Mn³⁺/Mn²⁺ couple is much more positive than that for Fe³⁺/Fe²⁺. 

Answer 1

The comparatively high value for Mn shows that Mn²⁺(d⁵ ) is particularly stable / Much larger third ionisation energy of Mn (where the required change is from d⁵ to d⁴ ).

Detailed Answer :

(a) Because Mn²⁺ is more stable than Mn³⁺ due to half-filled d⁵ configuration whereas Fe²⁺ becomes unstable after loosing an electron from half filled orbital.