Read Nitrogen's Oxidation-State Ladder Before Naming Its Oxides
Nitrogen forms a full ladder of oxides from N₂O (+1) to N₂O₅ (+5) — knowing which oxide is the acid anhydride of which oxoacid, and which contain an N-N bond, resolves most of this cluster's questions directly.
Chemistry questions first require the material, particles or reaction condition to be identified before a formula or rule is selected.
Nitrogen oxide oxidation states and their acid anhydrides
N₂O₃ is the anhydride of nitrous acid (HNO₂, N at +3); N₂O₅ is the anhydride of nitric acid (HNO₃, N at +5). NO (+2) is paramagnetic (an odd-electron molecule) and does not act as a reducing agent as readily as the lower oxides; N₂O₅, at nitrogen's highest common oxide oxidation state, cannot be oxidised further and so cannot act as a reducing agent at all.
Which nitrogen oxides retain an N-N bond
N₂O, N₂O₃ and N₂O₄ all retain a direct N-N bond in their structure; N₂O₅ does NOT — its structure is ionic-like, built from NO₂⁺ and NO₃⁻ in the gas phase, with no direct N-N connection. This single fact resolves 'which oxide lacks an N-N bond' questions immediately.
Common hydride and salt preparations
NH₄NO₂ decomposes on heating to N₂ (not NH₃) — a genuine exception among ammonium salts, most of which DO release NH₃ on heating (like (NH₄)₂SO₄, (NH₄)₂CO₃, NH₄Cl). Aqueous ammonia contains mostly NH₃ molecules with only a small equilibrium concentration of NH₄⁺ and OH⁻, which is why it behaves as a weak base rather than fully ionising.
Industrial nitrogen chemistry: Haber and Ostwald processes
The Haber process (N₂ + 3H₂ ⇌ 2NH₃) uses an iron-oxide catalyst (Fe₂O₃, often promoted with other oxides), not platinum. The Ostwald process converts NH₃ to HNO₃ through catalytic OXIDATION of ammonia (4NH₃ + 5O₂ → 4NO + 6H₂O, then further oxidation and hydration) — the direction is oxidation, not reduction or hydrolysis, since nitrogen's oxidation state rises from -3 in NH₃ to +5 in the final HNO₃.
OlympIQ exam lens
- ✓N₂O₃ is the anhydride of HNO₂ (nitrous acid); N₂O₅ is the anhydride of HNO₃ (nitric acid).
- ✓N₂O, N₂O₃, N₂O₄ retain a direct N-N bond; N₂O₅ does not.
- ✓NH₄NO₂ is the exception that decomposes to N₂ (not NH₃) on heating, unlike most other ammonium salts.
- ✓The Haber process uses an iron-oxide catalyst; the Ostwald process is an oxidation of ammonia, not a reduction or hydrolysis.
Don't assume every ammonium salt releases NH₃ on heating — NH₄NO₂ is a genuine exception, decomposing instead to N₂ and water, which is exactly the kind of exception these questions test.
Ready to try the pattern?
100% coverage across the 17 linked questions.
Practise 17 linked questions