Question

If $F{e}^{3+}+y^{4-}\rightleftharpoons Fe{Y}^{\ominus };K_f=1.3\times {10}^{25}$

$F{e}^{3+}+Y^{4-}\rightleftharpoons Fe{Y}^{2-};K_f=2.1\times {10}^{14}$

And $F{e}^{3+}+e^{-}\rightleftharpoons F{e}^{2+};E^{\ominus }=+0.77V$

$E^{\ominus }$ for $Fe{Y}^{\ominus }+e^{-}\to Fe{Y}^{2-}$ :

• A. $0.13$ V
• B. $0.26$ V
• C. $1.2$ V
• D. $1.6$ V

Answer 1

The correct option is A $0.13$ V

For $Fe{Y}^{\ominus }+e^{-}\to Fe{Y}^{2-}$,

The change is
$F{e}^{3+}+e^{-}\to F{e}^{2+}$
$E_{F{E}^{3+}|Fe{Y}^{2-}|Fe{Y}^{\ominus }}^{\ominus }$
$=E_{FE|F{e}^{2+}}^{\ominus }+\frac{0.059}{1}log\frac{\left[Fe{Y}^{2-}\right]\left[F{e}^{3+}\right]}{\left[Fe{Y}^{\ominus }\right]\left[F{e}^{2+}\right]}$
$=0.77+\frac{0.059}{1}log\frac{2.1\times {10}^{14}}{1.3\times {10}^{25}}=0.77-0.64=0.13V$