Answer:
c. 8, product side
Explanation:
In order to balance a redox reaction we use the ion-electron method, which has the following steps:
Step 1: identify oxidation and reduction half-reaction.
Oxidation: MnO₄⁻(aq) → Mn²⁺(aq)
Reduction: Br⁻(aq) → Br₂(l)
Step 2: perform the mass balance adding H⁺ and H₂O where necessary
8 H⁺(aq) + MnO₄⁻(aq) → Mn²⁺(aq) + 4 H₂O(l)
2 Br⁻(aq) → Br₂(l)
Step 3: perform the electrical balance adding electrons where necessary.
8 H⁺(aq) + MnO₄⁻(aq) + 5 e⁻ → Mn²⁺(aq) + 4 H₂O(l)
2 Br⁻(aq) → Br₂(l) + 2 e⁻
Step 4: multiply both half-reactions by numbers that secure that the number of electrons gained and lost are the same.
2 × (8 H⁺(aq) + MnO₄⁻(aq) + 5 e⁻ → Mn²⁺(aq) + 4 H₂O(l))
5 × (2 Br⁻(aq) → Br₂(l) + 2 e⁻)
Step 5: add both half-reactions side to side.
16 H⁺(aq) + 2 MnO₄⁻(aq) + 10 e⁻ + 10 Br⁻(aq) → 2 Mn²⁺(aq) + 8 H₂O(l) + 5 Br₂(l) + 10 e⁻
16 H⁺(aq) + 2 MnO₄⁻(aq) + 10 Br⁻(aq) → 2 Mn²⁺(aq) + 8 H₂O(l) + 5 Br₂(l)
