25
+0 34
Explain the irregularity in the above values The E
o (M
2+/M) values are not regular which can be explained from
the irregular variation of ionisation enthalpies (
i
i

1 
2
H
H ) and also
the sublimation enthalpies which are relatively much less for
manganese and vanadium Why is the E
o value for the Mn
3+/Mn
2+ couple much more positive
than that for Cr
3+/Cr
2+ or Fe
3+/Fe
2+