For `(M)^(2 *) / (M)` and `(M)^(3+) / (M)^(2+)` systems the `(E)^(0)` values for some metals are as follows: `(C)^(2+) / (Cr)` `(Cr)^(t) / (Cr)^(2+) -0.4 (~V)` Use this data to comment upon: i. the stability of Feitin acid solution as compared to that of `(Cr)^(3+)` or `(Mn)^(2)+` ii. the ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.

Explanation

i. .(Cr)^(3+) / (Cr)^(3+). has a negative reduction potential. Hence, .(Cr)^(3+). ion cannot be reduced to .(Cr)^(2+). ion, i.e. .(Cr)^(3+). ion is most stable. .(Mn)^(3) /. .(Mn)^(2+). has large positive .(E)^(circ). value. Hence .(Mn)^(3+). can be easily reduced to .(Mn)^(2+).
.(Fe)^(2+). is positive, but small. Hence .(Fe)^(3+). is more stable than .(Mn)^(3+). bat less stable than .(Cr)^(3+).
ii. .Oxidation potentials for the given pairs will be .+0.9 (~V),+1,2 (~V). and .+0.4. volt. Thus the order of their getting oxidized will be in the order .dot(M)_(n)gtC rgtF e.