19 . Dinitrogen : Preparation : heat NH4 Cl ( aq ) + NaNO2 ( aq ) → N2 ( g ) + 2H2 O ( l ) + NaCl ( aq )
heat ( NH4 ) 2 Cr2 O7 →
N2
+ 4H2 O + Cr2
O3
( ) heat
Ba N3 2
→ Ba + 3 N2
Properties :
It is a colouless , odourless , tasteless and non – toxic gas . It is chemically un-reactive at ordinary temperature due to triple bond in
N ≡ N which has high bond dissociation energy .
20 . Ammonia : Ammonia molecule is trigonal pyramidal with nitrogen atom at the apex . It has 3 bond pairs and 1 lone pair . N is sp 3
hybridised .
Preparation : Haber ’ s process :
N2 ( g ) + 3H2 ( g ) YZZZZZZX2 NH3 ( g ) Pressure = 200 x10 5 Pa fH o = − 46.1 kJ mol −1
Temperature = 773 K Catalyst is FeO with small amounts of K2O and Al2O3