13. Which of the following nitrogen oxides do not contain N#N bonds?
a. N2O5
b. N2O4
c. N2O
d. all of the above
The correct answer is d. all of the following. None of N2O5, N2O4, or N2O contain an N≡N triple bond between nitrogen atoms.
Option Analysis
N2O5 Structure
Dinitrogen pentoxide exists as discrete NO₂⁺ and NO₃⁻ ions in solid state, with no direct N-N connection. In gas phase, its Lewis structure shows two NO₂ groups linked by bridging oxygens, forming covalent and coordinate bonds (N-O-N) without any N≡N.
N2O4 Structure
Dinitrogen tetroxide features two nitrogen atoms connected by a single N-N bond (length 1.78 Å, longer than typical N-N single bond). Each N bonds to two O atoms via double/single bonds (O=N-N=O resonance), lacking a triple N≡N bond.
N2O Structure
Nitrous oxide shows linear resonance structures: ⁻N=N⁺=O ↔ N≡N⁺-O⁻. The N-N bond order averages 2.0-2.5 (distance 1.12 Å, between N=N and N≡N), not a pure triple bond as in free N₂.
Bond Type Summary
| Oxide | N-N Bond Present | Bond Order/Type | Contains N≡N? |
|---|---|---|---|
| N₂O₅ | No | None (N-O-N bridges) | No |
| N₂O₄ | Yes | Single (1.78 Å) | No |
| N₂O | Yes | ~2-2.5 (resonance) | No |
N≡N triple bonds appear in free N₂ (bond energy 942 kJ/mol), but these oxides use lower-order N-N bonds due to oxygen coordination. This distinction aids CSIR NET questions on molecular geometry and bonding.
