Chemistry

Nitrogen's oxidation state in dilute nitric acid depends on what product forms—and that's determined by how much oxidizing power is available. With very dilute $\text{HNO}_3$, there's limited nitric acid to act as an oxidizer, so zinc reduces nitrogen to a lower oxidation state than in concentrated acid. The key is recognizing that dilute conditions favor reduction to $\text{NH}_4^+$ (where N is $-3$) rather than $\text{NO}_2$ or $\text{NO}$, making this a more dramatic reduction than you might initially expect.

Nitrogen's oxidation state in dilute nitric acid depends on what product forms—and that's determined by how much oxidizing power is available. With very dilute $\text{HNO}_3$, there's limited nitric acid to act as an oxidizer, so zinc reduces nitrogen to a lower oxidation state than in concentrated acid. The key is recognizing that dilute conditions favor reduction to $\text{NH}_4^+$ (where N is $-3$) rather than $\text{NO}_2$ or $\text{NO}$, making this a more dramatic reduction than you might initially expect.