Answer to Question #150736 in General Chemistry for diana

Question

Balance the reaction in acid and base medium using half reaction method.

1. Fe⁺² + MnO4ˉ → Fe⁺³ + Mn⁺²

Answer 1

In acidic medium:

Half reactions

I. Fe²⁺ ---> Fe³⁺ (oxidation)

II. MnO₄^- ----> Mn²⁺ (reduction)

Balancing the equations atomically:

III. Fe²⁺ -----> Fe³⁺

IV. MnO₄^- + 8H⁺ ----> Mn²⁺ + 4H₂O

Balancing the equations electrically:

V. Fe ²⁺-----> Fe³⁺ + e^-

VI. MnO₄^- + 8H⁺ + 5e^- -----> Mn²⁺ + 4H₂O

Multiply V by 5 to balance electrons.

VII. 5Fe²⁺ ----> 5Fe³⁺ + 5e^-

VI. MnO₄^- + 8H⁺ + 5e^- -----> Mn²⁺ + 4H₂O

Add equations VI and VII

Net ionic equation in acidic medium:

5Fe²⁺ + MnO₄^- + 8H⁺ -----> 5Fe³⁺ + Mn²⁺ + 4H₂O

In basic medium.

To balance in basic medium, add 8OH^- to both sides of the net ionic equation in the acidic medium.

5Fe²⁺ + MnO₄^- + 8H⁺ + 8OH^- ----> 5Fe³⁺ + Mn²⁺ + 4H₂O + 8OH^-

5Fe²⁺ + MnO₄^- + 8H₂O ----> 5Fe³⁺ + Mn²⁺ + 4H₂O + 8OH^-

Net ionic equation in basic medium:

5Fe²⁺ + MnO₄^- + 4H₂O ----> 5Fe³⁺ + Mn²⁺ + 8OH^-