Q.Explain why Cr²⁺ is strongly reducing while Mn³⁺ is strongly oxidizing.

Step 1. For chromium: E°(Cr³⁺/Cr²⁺) = -0.41 V, a negative value, meaning the +3 state is thermodynamically preferred over +2. Cr²⁺, therefore, is thermodynamically driven to lose an electron and become Cr³⁺ -- i.e. Cr²⁺ readily acts as a REDUCING agent (donating an electron to some other species while itself being oxidised to the more stable Cr³⁺).

Step 2. For manganese: E°(Mn³⁺/Mn²⁺) = +1.51 V, a strongly positive value, meaning the +2 state is very strongly preferred over +3. This is because Mn²⁺ (3d⁵) reaches the extra-stable, exactly half-filled configuration, while Mn³⁺ (3d⁴) does not. Mn³⁺, therefore, is thermodynamically driven to gain an electron and become Mn²⁺ -- i.e. Mn³⁺ readily acts as an OXIDISING agent (accepting an electron from some other species while itself being reduced to the more stable Mn²⁺). …

Compare the M³⁺/M²⁺ reduction potentials for Cr and Mn, and explain the resulting redox character (reducing vs oxidising) in terms of which oxidation …

• Explaining Cr²⁺'s reducing character and Mn³⁺'s oxidising character without connecting either to the underlying d-electron configuration stability (3d …