Question

Balance the redox reaction occurring in basic solution.

Cl2(g)+Mn2+(aq)?MnO2(s)+Cl?(aq)

Express your answer as a chemical equation. Identify all of the phases in your answer.

Answer 1

Given,

Cl₂(g) + Mn²⁺(aq) MnO₂(s) + Cl^-(aq)

Step 1) Separating the half-reactions.

Cl₂(g) Cl^-(aq) ------ Reduction half-reaction

Mn²⁺(aq) MnO₂(s) ------Oxidation half-reaction

Step 2) Balance the atoms other than oxygen and hydrogen.

Cl₂(g) 2Cl^-(aq)

Mn²⁺(aq) MnO₂(s)

Step 3) Balance the oxygen atoms by adding H₂O(l) and balance the hydrogen atoms by adding H⁺(aq) to both half-reactions.

Cl₂(g) 2Cl^-(aq)

2H₂O(l) + Mn²⁺(aq) MnO₂(s) + 4H⁺(aq)

Step 4) Balance the charge by adding electrons to both the half-reactions.

2e^- + Cl₂(g) 2Cl^-(aq)

2H₂O(l) + Mn²⁺(aq) MnO₂(s) + 4H⁺(aq) + 2e^-

Step 5) Add both the half-reactions.

2e^- + Cl₂(g) 2Cl^-(aq)

2H₂O(l) + Mn²⁺(aq) MnO₂(s) + 4H⁺(aq) + 2e^-

^{--------------------------------------------------------------------------------}

Cl₂(g) + 2H₂O(l) + Mn²⁺(aq) 2Cl^-(aq) + MnO₂(s) + 4H⁺(aq)

Step 6) Add 4OH^-(aq) to both the sides, since we need to balance the reaction in basic solution.

4OH^-(aq) + Cl₂(g) + 2H₂O(l) + Mn²⁺(aq) 2Cl^-(aq) + MnO₂(s) + 4H⁺(aq) + 4OH^-(aq)

Thus,

4OH^-(aq) + Cl₂(g) + 2H₂O(l) + Mn²⁺(aq) 2Cl^-(aq) + MnO₂(s) + 4H₂O(l)

Thus,

Cl₂(g) + Mn²⁺(aq) + 4OH^-(aq) 2Cl^-(aq) + MnO₂(s) + 2H₂O(l) -------- Balanced redox reaction in basic solution.