Question

The E° value for the Mn³⁺/Mn²⁺ couple is more positive than that of Cr³⁺/Cr²⁺ or Fe³⁺/Fe²⁺ due to change of

• A. d⁵ to d⁴ configuration
• B. d⁵ to d² configuration
• C. d⁴ to d⁵ configuration
• D. d³ to d⁵ configuration

Answer 1

The Correct Option is C

1. $Mn^{3+}$ has a $d^4$ configuration, which upon reduction to $Mn^{2+}$ becomes $d^5$, a half-filled stable configuration.
2. This stability contributes to the more positive $E^o$ value for $Mn^{3+}/Mn^{2+}$ compared to Cr or Fe.