Balance the redox reaction in acidic conditions.

Question

Balance the following reaction using the lowest possible whole number coefficients, in acidic conditions.

 Bi₂O₄(aq) +  H₃PO₂(aq) +  H⁺(aq) +  H₂O(l) +  OH⁻(aq) →  BiO⁺(aq) +  H₃PO₃(aq) +  H⁺(aq) +  H₂O(l) +  OH⁻(aq)

Answer 1

Bi₂O₄(aq) + H₃PO₂(aq) + H⁺(aq) + H₂O(l) + OH⁻(aq) => BiO⁺(aq) + H₃PO₃(aq) + H⁺(aq) + H₂O(l) + OH⁻(aq)

Since the question asks to balance in acid (H⁺), not sure what OH^- is doing in the equation. Maybe someone else will weigh in on this.

Half reaction method

Reduction half reaction:

Bi₂O₄ ==> BiO⁺ (Bi goes from +4 to +3)

Bi₂O₄ ==> 2BiO⁺ + 2H2O .. balanced for Bi and O

Bi₂O₄ + 4H⁺ ==> 2BiO⁺ + 2H2O .. balanced for Bi, O and H (using acid)

Bi₂O₄ + 4H⁺ + 2e- ==> 2BiO⁺ + 2H2O .. balanced half reaction

Oxidation half reaction:

H₃PO₂ ==> H₃PO₃ (P goes from +1 to +3)

H₃PO₂ + H2O ==> H₃PO₃ .. balanced for P and O

H₃PO₂ + H2O ==> H₃PO₃ + 2H⁺ .. balanced for P, O and H

H₃PO₂ + H2O ==> H₃PO₃ + 2H⁺ + 2e- .. balanced half reaction

Add the 2 balanced half reactions together, and combine/cancel like terms:

Bi₂O₄ + 4H⁺ + 2e- ==> 2BiO⁺ + 2H2O

H₃PO₂ + H2O ==> H₃PO₃ + 2H⁺ + 2e-

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Bi₂O₄ + H₃PO₂ + 2H⁺ ==> 2BiO⁺ + H2O + H₃PO₃ .. balanced redox in acid