Which is a stronger reducing agent Cr2+ or Fe2+ and why?
The following reactions are involved when Cr2+ and Fe2+ act as reducing agents.
`Cr^(2+) -> Cr^(3+)Fe^(2+) -> Fe^(3+)`
The `E_((Cr^(3+))/(Cr^(2+)))^@` value is -0.14 V and `E_(" "(Fe^(3+))/(Fe^(2+)))^@` is + 0.77 V. This means that Cr2+ can be easily oxidized to Cr3+, but Fe2+ does not get oxidized to Fe3+ easily. Therefore, Cr2+ is a better reducing agent that Fe3+.
Cr2+ is a stronger reducing agent than Fe2+. This is because E°(Cr3+/Cr2+) is negative (- 0.41V) whereas E°(Fe3+/Fe2+) is positive (+ 0.77 V). Thus, Cr2+ is easily oxidised to Fe3+ but Fe2+ cannot be easily oxidised to Fe3+.