Nitrogen Family : Oxides of Nitrogen

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  \underrightarrow { \quad \Delta \quad } 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  \xrightarrow [ \quad 85{ 0 }^{ 0 }C\quad ]{ Pt } } 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  \underrightarrow { \quad 673\quad K\quad }   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