JEE Main · 2013 · 07 Apr 2013 · Offline · d and f Block Elements

Four successive members of the first row transition elements are listed below with atomic numbers. Which one of them is expected to have the highest

E_{M^{3 +} / M^{2 +}}^{0}

value?

Answer: (C)

Solution

The ion whose

M X^{3 +}

is most eager to fall back to

M X^{2 +}

carries the highest standard reduction potential. Among these four, cobalt stands out with

E_{Co X^{3 +} / Co X^{2 +}}^{\circ} \approx 1.97 V

, well above manganese, iron or chromium, because

Co X^{3 +}

is strongly oxidising. Cobalt therefore has the highest

E_{M X^{3 +} / M X^{2 +}}^{\circ}

value.

JEE Main · 2013 · 07 Apr 2013 · Offline · Single correct option