Question

Which of following complex has higher ${\Delta }_o$ value ?

• A. ${\left[Fe{\left(H_{2}O\right)}_6\right]}^{3+}$
• B. ${\left[Fe{\left(H_{2}O\right)}_6\right]}^{2+}$
• C. ${\left[Fe{\left(H_{2}O\right)}_6\right]}^{3-}$
• D. all have equal

Answer 1

The correct option is C ${\left[Fe{\left(H_{2}O\right)}_6\right]}^{3-}$

${\left[Fe{\left(H_{2}O\right)}_6\right]}^{3+}$
Fe has an oxidation state of $+3$.
${\Delta }_o=(-2/5)3+3/5\ast 2=0$
${\left[Fe{\left(H_{2}O\right)}_6\right]}^{2+}$
Fe has an oxidation state of $+2$.
${\Delta }_o=(-2/5)4+3/5\ast 2=-0.4$
${\left[Fe{\left(H_{2}O\right)}_6\right]}^{3-}$
Fe has an oxidation state of $-3$.
${\Delta }_o=(-2/5)6+3/5\ast 3=-0.6$