Question

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 $E_{M^{3+}/M^{2+}}$ value?

• A. $Cr(Z=24)$
• B. $Mn(Z=25)$
• C. $Fe(Z=26)$
• D. $Co(Z=27)$

Answer 1

The correct option is D $Co(Z=27)$

$E_{M{n}^{3+}/M{n}^{2+}}=1.57V$

$E_{C{r}^{3+}/C{r}^{2+}}=-0.41V$

$E_{F{e}^{3+}/F{e}^{2+}}=0.77V$

$E_{C{o}^{3+}/C{o}^{2+}}=1.97V$

So $Co$ has highest $E_{M^{3+}/M^{2+}}$ value.

Hence, the correct option is $D$.