For `M^(2+)|M` and `M^(3+)|M^(2+)` systems the `E^(0)` values for some metals are as follows :
`{:(Cr^(2+)"|"Cr,,-0.9V,,Cr^(3+)|Cr^(2+),,-0.4V),(Mn^(2+)"|"Mn,,-1.2V,,Mn^(3+)|Mn^(2+),,+1.5V),(Fe^(2+)"|"Fe,,-0.4V,,Fe^(3+)|Fe^(2+),,+0.8V):}`
Use this data to comment upon :
the stability of `Fe^(3+)` in acid solution as compared to that of `Cr^(3+)` or `Mn^(3+)`

Explanation

We know that, greater the reduction potential of a system `(M^(3+)|M^(2+))`, higher is the tendency its highest `(M^(3+))` to undergo reduction. Thus, `Mn^(3+)` with highest reduction potential would be most readily reduced to `Mn^(2+)` and hence, is least stable. The negative reduction potential of `Cr^(3+)|Cr^(2+)` system shows that `Cr^(3+)` ion has the least tendency to undergo reduction to `Cr^(2+)` , and hence, is most stable. So stability sequence is : `Mn^(3+)lt Fe^(3+)lt Cr^(3+)`.