NITROGEN
- exists as diatomic molecule, N2
:N=N:
- boils at -196oC and freeze at -210oC
- stable molecule, only reacts directly with Li at room temperature to form Li3N.
Preparation:
- from atmospheric nitrogen (78% )
- from the reaction between NH4Cl and NaNO2
NH4+(l) + NO2-(l) ------> N2(g) + 2H2O(l)
Uses:
- for the preparation of ammonia
- for oxygen-free condition, inert reaction condition.
-in electronic instrumental industries.
- liquid nitrogen used as freezing agent in food industries.
Ionic compounds (nitride)
6Li(s) + N2(g) ----------> 2Li3N
heat
3M + N2(g) --------------> M3N2
(M = Mg, Ca, Sr, Ba)
Reaction of nitride with water
Li3N(s) + 3H2O(l) ---------> 3LiOH(l) + NH3(g)
Mg3N2(s) + 6H2O(l) ----------> 3Mg(OH)2(s) + 2NH3(g)
Covalent compounds of nitrogen
Nitrogen reacts with non metals to form covalent nitrogen compounds
Fe
N2(g) + 3H2(g) --------------> 2NH3(g)
2NH3 + NaOCl ------> N2H4 + NaCl + H2O
NaNO2 + NaHSO3 + SO2 + 2H2O ---------> 2NaHSO3 + NH2OH
heat
NH4NO2 -------------> N2 + 2H2O
heat
NH4NO3 ------------> N2O + 2H2O
4NH3 + 5O2 --------> 4NO + 6H2O
-30oC
NO + NO2 -----------> N2O3
2NO + O2 ----------> 2NO2  N2O4
3NO2 + H2O -------> 2HNO3 + NO
Ammonia
- colourless gas
- boils at -33.35oC and freeze at -77.7oC.
..
N
H  H
H
pyrimidal structure
- polar molecule and very soluble in water.
NH3 + H2O ==== NH4+ + OH- a saturated solution of ammonia containing 28% NH3 in weight which is about 15M
- ammonia solution is basic.
- NH3 as proton donor
Na + NH3 -------> NaNH2 in non polar solvent
NH2- + H2O ----------> NH3 + OH(NH2- strong base)
- NH3 as proton acceptor
NH3 + HCl --------> NH4Cl + H2O
NH4Cl + H2O -------> NH3 + H2O (hydrolysis)
Preparation
N2 + 3H2 ------------> 2NH3 (Haber process)
CaO + 2NH4Cl -----------> 2NH3 + CaCl2 + H2O
NaOH + NH4Cl ----------> NH3 + NaCl + H2O
OHCaNCN + 3H2O -------> CaCO3 + 2NH3
Calcium cyanamide
Reaction:
Pt, 900oC
4NH3(g) + 5O2(g) ------------------> 4NO(g) + 6H2O(g) (Ostwald Process)
2NO(g) + O2(g) ----------> 2NO2(g)
3NO2 (g) + H2O(l) ----------> 2H+(l) + 2NO3-(l) + NO(g)
- Ammonium compounds
NH3 + HCl ------> NH4Cl
- ammonium compounds are not stable
NH4X ---------> NH3 + H+ + XHYDRAZINE, N2H4
- Formula structure
H
H

HN  NH
- Toxic solution
- boils at 114oC and freeze at 2oC.
Preparation:
2NH3 + NaOCl --------> N2H4 + NaCl + H2O
X = halide, CO22- , S2-
Reaction:
N2H4 + H2O === N2H5+ + OHHydrazinium ion
N2H4 + 2I2 + 4OH- -------> N2 + 4H2O + 4IN2H4 + O2(g ) ---------> N2(g) + 2H2O(g)
HYDROXYLAMINE, NH2OH
- formula structure
H
NOH
H
Preparation:
NaNO2 + NaHSO3 + SO2 + 2H2O ---------> 2NaHSO4 + NH2OH
Reaction:
15oC
NH2OH ---------> NH3 + N2 + NO + H2O
NH2OH + H2O === NH3OH+ + OHNH2OH + HCl ------> NH3OH+ClHYDROGEN AZIDE/ HYDRAZOIC ACID
N2H5+ + HNO3 ----> HN3 + H+ + 2H2O
2NaNH2 + N2O ----> NaN3 + NaOH + NH3
175oC
3NaNH2 + NaNO3 ---------> NaN3 + 3NaOH + NH3
- STRUCTURE
N==N==N
H
- colorless liquid, boils at 37oC
- weak acid
- oxidising and reducing agents
3NH4+ ==== HN3 + 11H+ + 8e
NH4+ + N2 === HN3 + 3H+ + 2e
HN3 === 3/2N2 + H+ + e
- form metal azide such as NaN3, AgN3, KN3, PbN3
NITROUS OXIDES
- Structural formula
:N=N=O:  NOO:
- also known as ‘laughing gas’
Preparation :
heat
NH4NO3 ------------> N2O(g) + 2H2O(g)
Reactions:
heat
N2O ----------->
N2 + O 2
NITRIC OXIDE and NITROGEN DIOXIDE
- as intermediate in the preparation of nitric acid from ammonia.
catalyst
NH3(g) + O2 ------------> NO(g)
O2
H2O
HNO3(c) + NO(g)
NO2(g)
Characteristics:
- nitric oxide is a reactive colorless gas
- nitrogen dioxide is a orange gas and toxic
- Structure
N
O
N
O
O
O:
In gas phase, it form dimer, dinitrogen tetroxide, N2O4
N2O4 – colorless liquid and with low b.p.
N2O4 is a good oxidising agent
DINITROGEN TRIOXIDE
Preparation:
NO + NO2 --------> N2O3
- blue liquid
- structure
O
O
N
N
O
- reacts with water
N2O3 + H2O -----> 2HNO2
- Nitrous acid is a wak acid and unstable
3HNO2 ------> HNO3 + H2O + 2NO
- prepared from the reaction of
NaNO2 + HCl -------> HNO2 + NaCl
- Nitrous acid reacts as oxidizing agent and reducing agent
H+ + 5HNO2 + 2MnO4- ------> 5NO3- + 2Mn2+ + 3H2O
2H+ + 2HNO2 + 2I- ----> I2 + 2NO + 2H2O
- Neutralisation of nitrous acid to form nitrite salt
HNO2 + NaOH ------> NaNO2 + H2O
- nitrite SALT also can be prepared from reduction of metal nitrate
heat
NaNO3 + Pb -------> NaNO2 + PbO
- Structure
O
N
N
O
O
O
-
- used as preservative
- toxic effect from NaNO2
NO2- + H+ -------> HNO2
HNO2 + R2-NH -----> R2-NNO
nitrosoamine
DINITROGEN PENTOXIDE
P2O5
2HNO3 ------------> N2O5 + H2O
- structure:
O
O
N
O
O
N
O
- N2O5 reacts with H2O
N2O5 + H2O ------> 2HNO3
- Nitric acid has wide range of uses
- fertilizer such as ammonium nitrate
- Explosive such as glyceryl trinitrite, TNT
- preservative
- nitric acid prepared from Ostwald process
- In laboratory
KNO3 + H2SO4 ------> KHSO4 + HNO3
- nitric acid – colorless liquid and decomposed at temperature above 0oC
4HNO3 -----> 4NO2 + 2H2O + O2
- nitric acid is a strong acid
- strong oxidising agent
Cu + 2NO3- + 4H+ ----> Cu2+ + 2NO2 + 2H2O
3Cu + 2NO3- + 8H+ ----> 3Cu2+ + 2NO + 4H2O
- with strong reducing agent and dilute solution
4Zn + NO3- + 10H+ ----> 4Zn2+ + NH4+ + 3H2O
- Mixture of HNO3 + HCl in ratio 1:3 is known as aqua regia
- used to dissolve inert metal such as gold and platinum
4H+ + 4Cl- + NO3- + Au -----> AuCl4- + NO +2H2O
NITROGEN-HALOGEN COMPOUNDS
- NF3, NCl3, NF2 and N2F2
Preparation:
electrolysis
NH4HF2 ----------------> NF3 + H2, N2O, N2, NH2F
Cl2 + 2NH3 -----> NH2Cl + NHCl2 + NCl3