Question

Give: E0Mn+7|Mn+2 = 1.5 V and E0Mn+4|Mn+2 = 1.2 V, then E0Mn+7|Mn+4 is

• A. 1.7 V
• B. 2.1 V
• C. 0.3 V
• D. 0.1 V

Answer 1

Answer: (A)

1.7 V

Answer 2

$Mn^{+7} +5e^{-} \to Mn^{2+}$
$Mn^{+4}+2e^{-} \to Mn^{2+}$
$Required \, equation$
$Mn^{+7}+3e^{-} \to Mn^{4+}$
$\therefore\, -3FE^{�-}=-7.5F+2.4F$
$\therefore\, E^{�-}=1.7 V$
$\Delta G^{�-}=-5 F 1.5,$
$\Delta G^{�-}=-2 F 1.2,$
$\Delta G^{�-}=-3FE^{�-}$