For $M^{2+} / M$ and $M^{3+} / M^{2+}$ systems,the ${E^{\Theta}}$ values for some metals are as follows:
$Cr^{2+} / Cr : -0.9 \ V$
$Cr^{3+} / Cr^{2+} : -0.4 \ V$
$Mn^{2+} / Mn : -1.2 \ V$
$Mn^{3+} / Mn^{2+} : +1.5 \ V$
$Fe^{2+} / Fe : -0.4 \ V$
$Fe^{3+} / Fe^{2+} : +0.8 \ V$
Use this data to comment upon:
$(i)$ The stability of $Fe^{3+}$ in acid solution as compared to that of $Cr^{3+}$ or $Mn^{3+}$ and
$(ii)$ The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.

(N/A) $(i)$ The ${E^{\Theta}}$ value for $Fe^{3+} / Fe^{2+}$ is $+0.8 \ V$,which is higher than that for $Cr^{3+} / Cr^{2+}$ $(-0.4 \ V)$ and lower than that for $Mn^{3+} / Mn^{2+}$ $(+1.5 \ V)$.
Since a higher reduction potential indicates easier reduction,$Mn^{3+}$ is most easily reduced to $Mn^{2+}$,followed by $Fe^{3+}$,and $Cr^{3+}$ is the least easily reduced.
Therefore,the stability of these ions in acid solution follows the order: $Mn^{3+} < Fe^{3+} < Cr^{3+}$.
$(ii)$ The reduction potentials for the $M^{2+} / M$ pairs are: $Mn^{2+} / Mn$ $(-1.2 \ V)$,$Cr^{2+} / Cr$ $(-0.9 \ V)$,and $Fe^{2+} / Fe$ $(-0.4 \ V)$.
Lower reduction potential indicates easier oxidation of the metal to its $M^{2+}$ ion.
Since the reduction potential values are in the order $Mn^{2+} / Mn < Cr^{2+} / Cr < Fe^{2+} / Fe$,the ease of oxidation follows the order: $Fe < Cr < Mn$.