Chemistry - Complete d-block Question with Solution | TestHub

The $E^{\circ }$ value of $M{n}^{+3}/M{n}^{+2}$ is much more positive than $C{r}^{+3}/C{r}^{+2}$ because $M{n}^{+3}$ has a $d^4$ configuration, which is unstable. After gaining an electron, it achieves the stable half-filled $d^5$ configuration. This makes $M{n}^{+3}$ a better oxidizing agent and gives it a more positive reduction potential. The third ionization enthalpy of Mn is also a contributing factor.