Balance the following half-reaction: (acidic) NO-3 (aq) → NO2 (aq) Express your answer as a half-reaction. Identify all of the phases in your answer.

2H⁺ + NO₃⁻ + 1e⁻ → NO₂ + H₂O

Explanation:

NO₃⁻ → NO₂

In left side, Nitrogen acts with + 5 by oxidation number

In right side, the oxidation number is + 4

This is a reduction reaction, because the oxidation number has decreased. So the N has gained electrons.

NO₃⁻ + 1e⁻ → NO₂

In acidic medium, we have to add water, where there are less oxygens to ballance the amount. We have 2 O in left side, and 3 O in right side, so we have to add 1 H₂O on left side.

NO₃⁻ + 1e⁻ → NO₂ + H₂O

Now that oxygens are ballanced, we have to ballance the hydrogens by adding protons in the opposite side

2H⁺ + NO₃⁻ + 1e⁻ → NO₂ + H₂O