Question

Give: E⁰_{Mn⁺⁷|Mn⁺²} = 1.5 V and E⁰_{Mn⁺⁴|Mn⁺²} = 1.2 V, then E⁰_{Mn⁺⁷|Mn⁺⁴} is

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

Answer 1

Answer: (A)

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