Q.

The E° value for the Mn3+/Mn2+ couple is more positive than that of Cr3+/Cr2+ or Fe3+/Fe2+ due to change of       [2024]

1 d5 to d4 configuration  
2 d5 to d2 configuration  
3 d4 to d5 configuration  
4 d3 to d5 configuration  

Ans.

(3)

Mn25[Ar]3d54s2

Mn3+[Ar]3d4

Mn2+[Ar]3d5

As d5 is a half-filled electronic configuration, it is highly stable configuration. Thus, Mn3+ has high tendency to get reduced to Mn2+.