Balancing Equations

Question

Balance the following equations for reactions in basic solution by the half-reaction method. Identify the oxidizing agent and the reducing agent in each.

(a) VO2 + (aq) + Cr(OH)3(s) → CrO4 2−(aq) + V(OH)3(s)

(b) Br2(l) → Br− (aq) + BrO3 − (aq)

(c) MnO4 2−(aq) + Fe(OH)2(s) → MnO2(s) + Fe(OH)3(s)

Answer 1

Wyzant doesn't provide enough space to do all three. So, I'll do one and hopefully you can do the others, or else just post the others as separate entries (posts).

(a).

VO₂ ==> V(OH)₃

VO₂ + H₂O ==> V(OH)₃ .. balanced for V and O

VO₂ + H₂O + H₂O ==> V(OH)₃ + OH^- .. balanced for V, O and H (using base, OH^-)

VO₂ + 2H₂O + e- ==> V(OH)₃ + OH^- .. balanced for V, O, H and charge = balanced reduction reaction

Cr(OH)₃ ==> CrO₄^2-

Cr(OH)₃ + H₂O ==> CrO₄^2- .. balanced for Cr and O

Cr(OH)₃ + H₂O + 5OH^- ==> CrO₄^2- + 5H₂O .. balanced for Cr, O and H (using base, OH-)

Cr(OH)₃ + H₂O + 5OH^- ==> CrO₄^2- + 5H₂O + 3e- .. balanced for Cr, O, H and charge = balanced ox. rxn.

3VO₂ + 6H₂O + 3e- ==> 3V(OH)₃ +3 OH^-

Cr(OH)₃ + H₂O + 5OH^- ==> CrO₄^2- + 5H₂O + 3e-

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3VO₂ + 6H₂O + 3e- + Cr(OH)₃ + H₂O + 5OH^- ==> 3V(OH)₃ +3 OH^- + CrO₄^2- + 5H₂O + 3e-

3VO₂ + 2H₂O + Cr(OH)₃ + 2OH^- ==> 3V(OH)₃ + CrO₄^2- .. balanced redox equation