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

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