Question

Which is the stronger reducing agent Cr²⁺ or Fe²⁺?

Answer 1

Cr²⁺ and Fe²⁺

Cr (Z = 24)

Electronic configuration – [Ar] 3d⁵ 4s¹

Cr²⁺ Electronic configuration – [Ar] 3d⁴ 4s⁰

Fe (Z = 26)

Electronic configuration – [Ar] 3d⁶ 4s²

Fe²⁺ Electronic confimiration – [Ar] 3d⁶ 4s⁰

If the standard electrode potential (E⁰) of metal is large and negative, the metal is a powerful reducing agent

$$\mathrm{Cr}{\phantom{A}}^{2+}+2\mathrm{e}{\phantom{A}}^{-}⟶\mathrm{Cr}$$

$$\mathrm{Fe}{\phantom{A}}^{2+}+2\mathrm{e}{\phantom{A}}^{-}⟶\mathrm{Fe}$$

E⁰ = – 0.91 V

E⁰ = – 0.44 V

By comparing the above equation, Cr²⁺ is a powerful reducing agent.