Transition and InnerTransition Elements - Result Question 122
####22. Four successive members of the first row transition elements listed below with atomic numbers. Which one of them is expected to have the highest $E _{M^{3+} / M^{2+}}^{\circ}$ value? (2013 Main)
(a) $Cr(Z=24)$
(b) $\operatorname{Mn}(Z=25)$
(c) $Fe(Z=26)$
(d) $Co(Z=27)$
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Solution:
- SRP value normally increases from left to right in the period of $d$-block elements. Some SRP value are exceptionally higher due to stability of product ion. e.g.
$$ E _{Mn^{3+} / Mn^{2+}}^{0}=+1.57 V ; E _{Co^{3+} / Co^{2+}}^{0}=+1.97 V $$
Thus, $E _{M^{3+} / M^{2+}}^{\circ}$ is highest for Co.
