Transcript Slide 1

Properties
• Dinitrogen is a colourless,
odourless, tasteless and non-toxic gas.
• It has two stable isotopes: 14N and 15N.
• It has a very low solubility in water and
low freezing and boiling points .
• Dinitrogen is rather inert at room temperature
because of the high bond enthalpy of N≡N bond.
• At higher temperatures, it directly combines with
• some metals to form predominantly ionic nitrides
and with non-metals,covalent nitrides.
6Li + N2 Heat → 2Li3N
3Mg + N2 Heat → Mg3N2
Reactivity towards hydrogen
• It combines with hydrogen at about 773 K in
the presence of a catalyst (Haber’s Process) to
form ammonia:
N2(g) + 3H2(g) → 2NH3(g);
AMMONIA
NH2 CONH2 + 2H2 O →( NH4)2 CO3 →2NH3 +
H2 O + CO2
2NH4Cl + Ca(OH)2 → 2NH3 + 2H2O +CaCl2
(NH4)2 SO4 + 2NaOH → 2NH3 + 2H2O +
Na2SO4
Haber’s process
• N2(g) + 3H2(g) →2NH3(g); Δf H0 – 46.1 kJ mol–1
• The optimum conditions
a pressure of 200 × 105 Pa (about 200 atm),
a temperature of ~ 700 K
and the use of a catalyst such as ironoxide
with small amounts of K2O and Al2O3 to
increase the rate of attainment of equilibrium
Flow chart diagram
PROPERTIES OF AMMONIA
• colourless gas with a pungent odour
• freezing and boiling points are 198.4 and
239.7 K respectively.
• In the solid and liquid states, it is associated
through hydrogen bonds and that accounts
for its higher melting and boiling points
Hydrogen Bonding in Ammonia
Ammonia gas is highly soluble in water
Structure of ammonia
• ammonia molecule is trigonal pyramidal with
the nitrogen atom at the apex.
• It forms ammonium salts with acids, e.g.,
NH4Cl, (NH4)2 SO4, etc.
• As a weak base, it precipitates the hydroxides
of many metals from their salt solutions.
2FeCl3 +NH4 OH aq→ Fe2 O 3. xH 2O + 3NH4Cl
LEWIS BASE
• The presence of a lone pair of electrons on the
nitrogen atom of the ammonia molecule makes it a
Lewis base.
It donates the electron pair and forms linkage with
metal ions and the formation of such complex
compounds finds applications in detection of metal
ions
such as Cu2+, Ag+:
• Cu2+ (aq) + 4 NH3(aq) → [Cu(NH3)4]2+ (aq)
• Ag + (aq) +Cl − (aq) →AgCl (s)white ppt)
Uses Of Ammonia
• Ammonia is used to produce various
nitrogenous fertilisers (ammonium nitrate,
urea, ammonium phosphate and ammonium
sulphate)
• and in the manufacture of some inorganic
nitrogen compounds like nitric acid. Liquid
ammonia is also used as a refrigerant
Oxides of Nitrogen
• Nitrogen forms a number of oxides in different
oxidation states
(1) Dinitrogen oxide [Nitrogen(I) oxide]
NH4NO3→ N2O +2H2O
colourless gas, neutral
(2) Nitrogen monoxide NO
[Nitrogen(II) oxide]
• 2NaNO2 + 2FeSO 4+ 3H 2SO4 → Fe 3(SO4)3 +
2NaHSO4 + 2H2 O + 2NO
colourless gas , neutral
Dinitrogen trioxide N2O3 [Nitrogen(III)
oxide
•
2NO + N2O → 2N2 O3
blue solid
Nitrogen dioxide NO2
[Nitrogen(IV) oxide]
673 K
2Pb(NO3)2 → 4NO2 +PbO
brown gas,
acidic
Dinitrogen tetroxide
[Nitrogen(IV) oxide]
N2O4
COOL
2NO2
→
HEAT
N2O4
colourless solid/ liquid, acidic
Dinitrogen pentoxide N2O5
Nitrogen(V) oxide]
•
4HNO3+ P4 O10 →4HPO3 + 2N2 O5
colourless solid, acidic
Lewis structure of NO2
LEWIS STRUCTURE OF N2O
LEWIS STRUCYURE OF NO
LEWIS STRUCTURE OF N2O5
LEWIS STRUCTURE OF N2O3
OXOACIDS OF NITROGEN
• Nitrogen forms oxoacids such as
H2N2O2 (hyponitrous acid),
HNO2 (nitrous acid) and
HNO3 (nitric acid).
Amongst them HNO3 is the most important
NITRIC ACID
• PREPARATION - LAB
• NaNO3 + H2 SO 4→ NaHSO4 + HNO3
MANUFACTURE
• On a large scale it is prepared by Ostwald’s process.
• This method is based upon catalytic oxidation of NH3 by
atmospheric oxygen.
Pt /Rh gauge catalyst
500K, 9 bar 2
4NH3( )g + 5 O 2(g) ⎯⎯⎯⎯⎯⎯⎯⎯→ 4NO( g) + 6H2 O (g)
(from air)
• Nitric oxide thus formed combines with oxygen giving NO2.
2NO g +O 2g → 2NO 2g
Nitrogen dioxide so formed, dissolves in water to give HN
3NO 2g + H2 O (l) →2HNO3(aq) + NO(g)
STRUCTURE OF NITRIC ACID
• In the gaseous state, HNO3 exists as a planar
molecule
Uses of nitric acid
• The major use of nitric acid
• in the manufacture of ammonium nitratefor
fertilisers and other nitrates for use in explosives
and pyrotechnics.
used for the preparation of nitroglycerin,
trinitrotoluene and other organic nitro
compounds.
Other major uses are in the pickling of stainless
steel,etching of metals and as an oxidiser in
rocket fuels
PHOSPHORUS
• Phosphorus is found in many allotropic forms, the
important ones being white, red and black.
• White phosphorus is a translucent white waxy
solid. It is poisonous, insoluble in water but
soluble in carbon disulphide and glows in dark
(chemiluminescence).
It dissolves in boiling NaOH solution in an inert
atmosphere giving PH3.
P 4+ 3NaOH + 3H 2O → PH 3+ 3NaH2 PO2
WHITE P
• White phosphorus is less stable and therefore,
more reactive and readily catches fire.
• because of angular strain in the P4 molecule
where the angles are only 60°
Red phosphorus
obtained by heating white phosphorus at 573K
in an inert atmosphere for several days.
• red phosphorus is much less reactive than
white phosphorus because It is polymeric,
consisting of chains of P4 tetrahedra linked
together . It does not glow in the dark