Question

Balance the oxidation–reduction half reactions for hydrogen peroxide and permanganate ion, respectively. Write the net ionic equation for the reaction between MnO4 – ions and H2O2 in acidic solution.

Answer 1

5 H₂O₂ + 6 H⁺ + 2 MnO₄⁻ → 5 O₂ + 2 Mn²⁺ + 8 H₂O

Step-by-step explanation:

In order to balance a redox reaction, we will use the ion-electron method.

Step 1: Identify both half-reactions

Oxidation: H₂O₂ → O₂

Reduction: MnO₄⁻ → Mn²⁺

Step 2: Perform the mass balance, adding H⁺ and H₂O where necessary.

H₂O₂ → O₂ + 2 H⁺

8 H⁺ + MnO₄⁻ → Mn²⁺ + 4 H₂O

Step 3: Perform the electrical balance, adding electrons where necessary.

H₂O₂ → O₂ + 2 H⁺ + 2 e⁻

8 H⁺ + MnO₄⁻ + 5 e⁻ → Mn²⁺ + 4 H₂O

Step 4: Multiply both half-reactions by numbers that secure that the number of electrons gained and lost are equal.

5 × (H₂O₂ → O₂ + 2 H⁺ + 2 e⁻)

2 × (8 H⁺ + MnO₄⁻ + 5 e⁻ → Mn²⁺ + 4 H₂O)

Step 5: Add both half-reactions and cancel what is repeated in both sides.

5 H₂O₂ + 16 H⁺ + 2 MnO₄⁻ → 5 O₂ + 10 H⁺ + 2 Mn²⁺ + 8 H₂O

5 H₂O₂ + 6 H⁺ + 2 MnO₄⁻ → 5 O₂ + 2 Mn²⁺ + 8 H₂O