Question

How are E° values helpful in explaining the stability of transition metal ions in aqueous medium?

Answer 1

1. The standard electrode potential (E°) values indicate the tendency of a transition metal ion to be reduced or oxidised in aqueous solution.
2. A higher positive E° value means the ion is more easily reduced; hence, the higher oxidation state is less stable.
3. Conversely, a negative or low positive E° means the ion is more stable in that oxidation state as it resists reduction.
4. For example, Cr³⁺ has a negative E° for Cr³⁺/Cr²⁺, showing Cr³⁺ is stable and not easily reduced.
5. Mn³⁺ has a large positive E°, indicating it is unstable and readily reduced to Mn²⁺.
6. Fe³⁺ has a moderately positive E°, so it is more stable than Mn³⁺ but less stable than Cr³⁺.

Therefore, E° values help predict which oxidation states are favored and stable in aqueous media for transition metals.