Balance the chemical reaction in basic conditions with lowest whole number cofficients.

Question

Unbalanced Equation:

As(s) + H₂BO₃⁻(aq) → AsO₂⁻(aq) + B(s)

Answer 1

As(s) + H₂BO₃⁻(aq) ==> AsO₂⁻(aq) + B(s)

We will use the half-reaction method...

Oxidation half reaction:

As(s) ==> AsO₂^-(aq) (As goes from 0 to +3, so it is being oxidized)

As(s) + 2H₂O(l) ==> AsO₂^-(aq) ... balanced for As and O

As(s) + 2H₂O(l) + 4OH^-(aq) ==> AsO₂^-(aq) + 4H₂O(l) ... balanced for As, O and H using base, OH^-

As(s) + 2H₂O(l) + 4OH^-(aq) ==> AsO₂^-(aq) + 4H₂O(l) + 3e- ... balanced half reaction

Reduction half reaction:

H₂BO₃⁻(aq) ==> B(s) (B goes from +3 to zero, so it is being reduced)

H₂BO₃⁻(aq) ==> B(s) + 3H₂O(l) ... balanced for B and O

H₂BO₃⁻(aq) + 4H₂O(l) ==> B(s) + 3H₂O(l) + 4OH^-(aq) ... balanced for B, O and H using base, OH^-

H₂BO₃⁻(aq) + 4H₂O(l) + 3e- ==> B(s) + 3H₂O(l) + 4OH^-(aq) ... balanced half reaction

Add the two half reactions together and combine/cancel like terms....

As(s) + 2H₂O(l) + 4OH^-(aq) ==> AsO₂^-(aq) + 4H₂O(l) + 3e-

H₂BO₃⁻(aq) + 4H₂O(l) + 3e- ==> B(s) + 3H₂O(l) + 4OH^-(aq)

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As(s) + H₂BO₃⁻(aq) ==> AsO₂^-(aq) + B(s) + H₂O(l) ... balanced redox equation