Oxides of nitrogen : Nitrogen combines with O2 under different conditions to form a number of binary oxides which differ with respect to the oxidation state of the nitrogen atom. The important oxides are N2O, NO, N2O3, NO2, N2O4 and N2O5.
Oxides of Nitrogen
Oxide | Oxidation State of N | Physical appearance | Structure |
Nitrous oxide (N2O) | +1 | Colourless gas | N ≡ N → O |
Nitric oxide (NO) | +2 | Colourless | N = O |
Dinitrogen trioxide (N2O3) | +3 | Blue solid | |
Dinitrogen tetraoxide (N2O4) | +4 | Colourless liquid | |
Nitrogen dioxide
(NO2) |
+4 | Brown gas | |
Dinitrogen pentoxide (N2O5) | +5 | Colourless gas |
Oxide of Nitrogen | Preparation |
Nitrous Oxide (N2O) | By heating ammonium nitrate upto 2400C |
NH4NO3 N2O + 2H2O | |
Collected over hot water. | |
Nitrous oxide (NO) | (a) By the action of cold dil. HNO3 on copper turnings (Laboratory method) |
3Cu + 8 dil. HNO3 → 3Cu(NO3)2 + 4H2O + 2NO | |
(b) By the action of H2SO4 on a mixture of FeSO4 and KNO3 (4:1) | |
2KNO3 + 5H2SO4 + 6FeSO4 2KHSO4 + 3Fe2(SO4)3 + 4H2O + 2NO | |
(c) By catalytic oxidation of ammonia. | |
4NH3 + 5O2 4NO + 6H2O | |
Dinitrogen trioxide(N2O3) | (a) By the action of 50% HNO3 on arsenious oxide.
2HNO3 + As2O3 + 2H2O NO + NO2 + 2H3AsO4 ↓ 250 K N2O3 |
Nitrogen dioxide (NO2) | (a) By heating nitrates of heavy metals, e.g., lead nitrate. |
2Pb(NO3)2 4NO2 + 2PbO + 2O | |
(b) By heating copper turnings with conc. HNO3. | |
Cu + 4 conc. HNO3 Cu(NO3)2 + 2H2O + 2NO2 | |
Dinitrogen pentoxide(N2O5) | (a) By dehydrating HNO3 with phosphorus pentoxide |
4HNO3 +P4O10 → 2N2O5 + 4 HPO3 |
(iii) Oxyacids of nitrogen
Oxyacids of nitrogen
Name of
oxoacid |
M. F. Formula M. F. | Structure | Oxidation State of N | Basicity | pKa | Nature |
Hyponitrous acid | H2N2O2 | +1 | 2(dibasic) | Very weak | Highly explosive | |
Nitrous acid | HNO2 | +3 | 1 (monobasic) | 3.3 | Unstable Weak acid | |
Nitric acid | HNO3 | +5 | 1 (monobasic) | -3.0 | Stable, Strong acid | |
Pernitric acid | HNO4 | +5 | 1 (monobasic) | Unstable and explosive |