Question

In aqueous solution, $Cr^{2+}$ is stronger reducing agent than $Fe^{2+}$. This is because

• A. $Cr^{2+}$ ion is more stable than $Fe^{2+}$
• B. $Cr^{3+}$ ion with $d^3$ configuration has favourable crystal field stabilization energy
• C. $Cr^{3+}$ has half-filled configuration and hence more stable
• D. $Fe^{3+}$ in aqueous solution is more stable than $Cr^{3+}$
• E. $Fe^{2+}$ ion with $d^6$ configuration has favourable crystal field stabilization energy

Answer 1

Answer: (B)

$\because Cr ^{3+}$ ion has $d ^{3}$ configuration $\left(t_{2 g}^{3} e _{g}^{0}\right)$, which makes $Cr ^{3+}$ stable by providing crystal field stabilisation energy. Thus, $Cr ^{2+}$ ion can easily changes to $Cr ^{3+}$ (i.e. get oxidised) and acts as a strong reducing agent.

$Cr ^{2+} \longrightarrow Cr ^{3+}+e^{-}$