Question

Write the ionic equations for the oxidizing action of (MnO_4^-) in acidic medium with : (I) (Fe^2+) ion (II) (I^-) ion

Hint:

In acidic medium, permanganate ion is reduced from Mn(VII) to Mn(II), making it one of the strongest oxidizing agents among common laboratory reagents.

Answer 1

Concept: Permanganate ion ((MnO_4^-)) is a powerful oxidizing agent in acidic medium. During oxidation reactions, manganese is reduced from oxidation state (+7) to (+2). The reduction half-reaction in acidic medium is: [ MnO_4^-+8H^++5e^- Mn^2++4H_2O ] This reduction is coupled with oxidation of the reacting species. (I) Oxidation of (Fe^2+)

Step 1: Oxidation half-reaction [ Fe^2+ Fe^3++e^- ]

Step 2: Balance electrons Multiplying by 5: [ 5Fe^2+ 5Fe^3++5e^- ]

Step 3: Add reduction half-reaction [ MnO_4^-+8H^++5e^- Mn^2++4H_2O ]

Step 4: Overall ionic equation [ MnO_4^-+8H^+ +5Fe^2+ Mn^2+ +5Fe^3+ +4H_2O ]

(II) Oxidation of (I^-)

Step 1: Oxidation half-reaction [ 2I^- I_2+2e^- ]

Step 2: Balance electrons Multiplying oxidation reaction by 5 and reduction reaction by 2: [ 10I^- 5I_2+10e^- ] [ 2MnO_4^-+16H^++10e^- 2Mn^2++8H_2O ]

Step 3: Add both equations [ 2MnO_4^- +16H^+ +10I^- 2Mn^2+ +5I_2 +8H_2O ]