Final answer:
The partial equation that represents an oxidation of nitrogen is NO₂ → N₂O₅, where the oxidation state of nitrogen increases from +4 to +5.
Step-by-step explanation:
The question asks which partial equation represents an oxidation of nitrogen. Oxidation refers to the loss of electrons or an increase in oxidation state by an atom, ion, or molecule. Given that:
- The oxidation number of nitrogen in NH₃ is -3.
- The oxidation state of nitrogen in N₂O₄ varies since it's a multiple oxidation states compound.
- The nitrogen in NO₃⁻ has an oxidation state of +5.
- The nitrogen in NO₂ has an oxidation state of +4, and in N₂O₅ nitrogen has an oxidation state of +5.
Using this information, we can see that the conversion from NO₂ to N₂O₅ represents an oxidation because the oxidation state of nitrogen increases from +4 to +5.