Response:
a. 3 Br₂(l) + 6 OH⁻(aq) → 5 Br⁻(aq) + BrO₃⁻(aq) + 3 H₂O
b. Br₂
c. Br₂
Clarification:
Balancing a redox reactionis performed using the ion-electron method.
Step 1: Identify both half-reactions.
Reduction: Br₂(l) → Br⁻(aq)
Oxidation: Br₂(l) → BrO₃⁻(aq)
Step 2: Perform mass balance. This reaction occurs in basic conditions, thus we must add OH⁻ and H₂O as needed.
0.5 Br₂(l) → Br⁻(aq)
6 OH⁻(aq) + 0.5 Br₂(l) → BrO₃⁻(aq) + 3 H₂O
Step 3: Ensure electrical balance by incorporating electrons when necessary.
1 e⁻ + 0.5 Br₂(l) → Br⁻(aq)
6 OH⁻(aq) + 0.5 Br₂(l) → BrO₃⁻(aq) + 3 H₂O + 5 e⁻
Step 4: Scale both half-reactions to ensure the electron counts balance out.
5 × (1 e⁻ + 0.5 Br₂(l) → Br⁻(aq))
1 × (6 OH⁻(aq) + 0.5 Br₂(l) → BrO₃⁻(aq) + 3 H₂O + 5 e⁻)
Step 5: Combine both half-reactions and simplify as appropriate.
5 e⁻ + 3 Br₂(l) + 6 OH⁻(aq) → 5 Br⁻(aq) + BrO₃⁻(aq) + 3 H₂O + 5 e⁻
3 Br₂(l) + 6 OH⁻(aq) → 5 Br⁻(aq) + BrO₃⁻(aq) + 3 H₂O
The species that undergoes reduction is identified as the oxidizer. The species that undergoes oxidation is termed the reducer. In this situation, Br₂ qualifies as both.