6. Elements of main group V. - Nitrogen and N-compounds
6.1. Nitrogen
6.1.1. Physical properties
6.1.2. Chemical properties
6.1.3. Occurrence
6.1.4. Production
6.1.5. Use
6.2. Hydrogen compouns of nitrogen
5.2.1. Ammonia, NH3
5.2.2. Hydrazine, H2N-NH2
5.2.3. Hydrazoic acid, HN3
5.2.4. Hydroxylamine, NH2OH
6.3. Oxides and oxyacids of nitrogen
6.3.1. Oxides of nitrogen
6.3.2. Nitrogen containing oxyacids
Nitrous acid
Nitric acid
6. Elements of main group V. - Nitrogen and N-compounds
Main group V:
N, P
As, Sb
Bi
Electronic configuration: ns2np3,
nonmetals
semimetals
metals
6.1. Nitrogen
6.1.1. Physical properties
- colourless, odourless gas,
- bp. -196°C
- unpolar, less polarizable, unreactive molecules
- bond energy: 946 kJ/mol 1σ + 2π
- EN 3,0
6.1.2. Chemical properties:
- at room temperature: 6Li + N2
- at high temperature:
2Li3N
lithium nitride
N2 + 3 H2
2NH3
- in its compounds: tetrahedral orientation of bondings, coordination
number: 4
6.1.3. Occurrence
Air: 78,095% N2
(20,939% O2,
0,935% noble gases,
0,031% CO2)
6.1.4. Production
- from liquified air (industry)
- on labor scale:
NH4NO2
N2 + 2H2O
6.1.5. Use
synthesis of ammonia:
N2 + 3H2
2NH3
6.2. Hydrogen compounds of nitrogen
6.2.1. Ammonia, NH3
- gas with pungent odour
- bp. -33°C,
- pyramidal structure
- easy liquefaction
- in liquid state:
- selfionization
2NH3
NH4+ + NH2-
- dissolution of alkali and earth alkali metals (blue solutions)
conducts the electric current
- in presence of Fe(NO3)3 catalyst: formation of alkali amides
2Na + 2NH3
2 NaNH2 + H2
- very well soluble in water, basic solution
H2O + NH3
NH4+ + OH- reaction with acids in aqueous solution, formation of ammonium salts:
HCl + NH3(aq)
NH4Cl
- combustible, it burns in oxygen:
3O2 + 4NH3
2N2 + 6H2O
- combustion in presence of platinum catalyst:
5O2 + 4NH3
4NO + 6H2O
- complex formation:
AgCl + 2NH3(aq)
- Detection: Nessler-reagent
- Use
- agriculture,
- production of fertilizers,
- in refrigerators
[Ag(NH3)2]Cl(aq)
6.2.2. Hydrazine, H2N-NH2
- liquid, bp. 113°C,
- base
- very strong reducing agent (oxidized to N2)
- combustible, great heat of combustion (rocket fuel)
6.2.3. Hydrazoic acid, HN3
- colourless liquid, unstable (risk of explosion), - bp. 36°C
- structure: linear arrangement of N atoms
- salts: azides; alkali azides: water soluble toxic substances
heavy metal azides: explosives, (e.g. Pb(N3)2)
6.2.4. Hydroxylamine, NH2OH
- mp. 33°C
- reacts with carbonyl compounds (
- weak reducing agent
Oxime)
6.3. Oxides and oxyacids of nitrogen
6.3.1. Oxides of nitrogen
- numerous oxides:
N2O, NO (N2O2) neutral oxides
NO2 (N2O4), N2O3, N2O5 acidic oxides
- stable molecules, except N2O5
- acidic oxides: form oxyacids in reaction with water
(= acid anhydrides)
N2O3 + H2O
2 HNO2
nitrous acid
N2O5 + H2O
2 HNO3
nitric acid
NO2 + H2O
HNO2 + HNO3
mixed anhydride
Dinitrogen oxide, N2O
(Dinitrogen-monoxide; „laughing gas”)
- colourless gas with sweet odour;
inhalation: narcosis
- preparation:
NH4NO3
N2O + 2H2O
(careful heating)
Nitrogen oxide, NO,
(Nitrogen monoxide),
gas, liquified
NO
N2O
N2O2
non paired electron, paramagnetic
diamagnetic
Colourless, toxic, very reactive gas, in air it becomes brown
2NO + O2
2NO2
- formation:
3Cu + HNO3
- preparation:
3Cu(NO3)2 + 2NO + 4H2O
4NH3 + 5O2
4NO + 6H2O
(Pt catalyst)
Nitrogen dioxide, NO2
2NO2
reddish brown gas
paramagnetic
N2O4
colourless liquid
diamagnetic
NO2/N2O4 ratio in equilibrium mixture at 64°C is 1:1
- mixed anhydride of HNO2 and HNO3:
2NO2 + 2NaOH
NaNO2 + NaNO3 + H2O
- Use: manufacture of nitric acid
(led into water in presence of O2)
Dinitrogen trioxide, N2O3
bp.: -10 °C
N2O3 + H2O
N2O3
2HNO2
NO + NO2
Dinitrogen pentoxide, N2O5
mp.: 30 °C
N2O5
N2O5 + H2O
2N2O5
NO3- + NO2+
2HNO3
4NO2 + O2
6.3.3. Nitrogen containing oxyacids
- Nitrous acid, HNO2
- unstable, exists only in aqueous solutions,
- aqueous solution: blue:
3HNO2
- oxidizing agents:
HNO3 + 2NO + H2O
H2S
I-
S
I2
- against stronger oxidizing agents it acts reducing:
-
NO2
- salts:
KMnO4
NO3-
nitrites
e.g. sodium nitrite, NaNO2
- detection (NO2-): Griess-Ilosvay reagent
- Nitric acid, HNO3
- liquid,
- in air it „fumes”,
- bp. 84°C
- azeotropic mixture with water:
69,2 (m/m)%, bp. 122°C
- in water-free state: neutral molecule
- electrolytic dissociation in water:
HNO3 + H2O
NO3- + H3O+
- protonation with cc. sulfuric acid:
HNO3 + H2SO4
H2NO3+
H2NO3+ + HSO4NO2+ + H2O
- decomposition of cc. nitric acid:
2HNO3
2NO2 + H2O + „O” when heated and illuminated
- strong oxidizing agent, reduced to NO or NO2
- hot cc. nitric acid: dissolution of some nonmetals (e.g. S, P, C, As) and
metals (except Au, Pt, Ir)
- „aqua regia”, royal water (3:1 mixture of cc.HCl and cc.HNO3)
HNO3 + 3HCl
Au + 2Cl + NOCl
2Cl + NOCl + 2H2O
AuCl3 + NO
- Fe, Al become passivated in cc. nitric acid
- Production:
4NO2 + O2 + 2H2O
4HNO3
- Salts: nitrates, all of them are soluble in water
by heating: release of oxygen (pyrotechnics)
sodium nitrate, NaNO3
potassium nitrate, KNO3
ammonium nitrate, NH4NO3
- Detection (NO3-): diphenylamine-test