Use the data to answer the following and also justify giving rason: `{:(," "Cr," "Mn," "Fe," "Co),(E_(M^(2+)//M)^0,-0.91,-1.18,-0.44,-0.28),(E_(M^(2+)//M^(2+))^0,-0.41,+1.57,+0.77,+1.97):}`
( a) Which is a stronger redusing agent in aqueous medium `Cr^(2) or Fe^(2+)` and why ?
( b) Which is the most stable ion in +2 oxidartion and why ?

Explanation

`Cr^2` is stronger reducting agent then `fe^(2+)` because `E^(@)_(Cx^(2+)//Cx^(2+)` is -ve (-0.14 V) whereas `E^(@)_(Fe^3+//Fe^(2+))` is + Ve (+0.77 V).
Thus `Cr^2+` is easily oxidized to `Fe^(3+)` but `Fe^(2+)` cannot be easily oxidized to `Fe^(3+)` .Hence `Cr^2` is stronger reducting agent than `Fe^(2+)`
( b ) `E^@` value for Mn(-118) is more negative than expected from gerneral trend due to extra stability of half filled `Mn^(++)`ion