The reduction potential E 0 , in V of MnO 4 - aq / Mn s is [Given: E MnO 4 - aq / MnO 2 s o = 1 . 68   V ;   E MnO 2 s / Mn 2 + aq o = 1 . 21   V ;     E Mn 2 + aq / Mn s o = - 1 . 03   V ] Truncate/round-off the value to TWO decimal places.
A. A
Given (1) MnO 4 - aq + 4 H + + 3 e ⟶ MnO 2 s + 2 H 2 O ; E ° = 1 . 68   V ΔG 1 ° = - 3   F 1 . 68 = - 5 . 04   F (2) MnO 2 s + 4 H + + 2 e ⟶ Mn 2 + ( aq )   + 2 H 2 O ; E ° = 1 . 21   V ΔG 2 ° = - 2   F 1 . 21 = - 2 . 42   F (3) Mn 2 + aq + 2 e ⟶ Mn s ; E ° = - 1 . 03   V ΔG 3 ° = - 2   F - 1 . 03 = + 2 . 06   F Adding 1 , 2 and 3 , MnO 4 - aq + 8 H + + 7 e ⟶ Mn s + 4 H 2 O ΔG o = ΔG 1 ° + ΔG 2 ° + ΔG 3 ° = - 5 . 04 - 2 . 42 + 2 . 06 F - 7   FE ° = - 5 . 40   F E ° = 0 . 77   V
Related: Chemistry — Electrochemistry · All PYQ Banks