ü Preparation
of Dinitrogen: Dinitrogen is
produced commercially by the
liquefaction and fractional distillation of air.
In the laboratory,
dinitrogen is prepared by treating an aqueous solution of ammonium chloride
with sodium nitrite.
NH4CI(aq) + NaNO2(aq) → N2(g) + 2H2O(l) + NaCl (aq)
It
can also be obtained by the thermal decomposition of ammonium dichromate.
(NH4)2Cr2O7
→Heat
N2 + 4H2O + Cr2O3
Very pure
nitrogen can be obtained by the thermal decomposition of sodium or barium
azide.
Ba(N3)2 → Ba + 3N2
Properties:
· Dinitrogen
is 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 ionic nitrides and with non-metals to form covalent nitrides.
·
N2 is a
colourless, odourless gas insoluble in water.
·
It is neither combustible nor a supporter
of combustion.
· 6Li + N2 →Heat 2Li3N
;
3Mg + N2 →Heat Mg3N2
· It combines with hydrogen at
about 773 K in the presence of a catalyst Fe (Haber’s Process) to form ammonia:
N2 +3H2
→ 2NH3
· Dinitrogen combines with
dioxygen at very high temperature (at about 2000 K)
to form nitric oxide
N2 + O2
→ 2 NO
Ø Uses:
1. The main use of dinitrogen is in the
manufacture of ammonia and other industrial
chemicals containing nitrogen (e.g., calcium cyanamide).
2. It also used to create an inert atmosphere in metallurgy.
3. Liquid
dinitrogen is used as a refrigerant to preserve biological materials, food
items and in cryosurgery.
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