Page 211 - Academic Press Encyclopedia of Physical Science and Technology 3rd InOrganic Chemistry

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20 Main Group Elements

are also produced in the atmosphere from nitrogen oxide ofnitrosoamines,compoundsthathavebeendemonstrated
pollutants (NO x ) and from NO produced during lightning to be carcinogenic.
storms:
R N H + HONO −→ R N N O + H 2 O
lightning | |
N 2 (g) + O 2 (g) −−−−→ 2NO (g) R R
A secondary amine A nitrosoamine, carcinogenic
2NO (g) + O 2 (g) → 2NO 2 (g) + heat
Orthonitric acid, H 3 NO 4 , which is analogous to or-
3NO 2 (g) + H 2 O → 2HNO 3 + NO (g)
thophosphoric acid, H 3 PO 4 , has not been prepared. The
hydrate of nitric acid, which is represented by the formula
Pure nitric acid, a colorless liquid that readily fumes in
H 3 NO 4 , has been identified by Raman spectroscopy to be
moistair,israrelyencountered;ratheritistheconcentrated
merely hydronium nitrate:
aqueous solution of commerce with which most persons
are familiar. A comparison of the physical properties of “H 3 NO 4 ” ≡ H 3 O + NO −
+
3
the pure acid versus the solution is made in the following
Successful attempts to synthesize orthonitrate salts of
tabulation:
sodium and potassium have been reported:
Anhydrous Concentrated silver
crucible
HNO 3 HNO 3 NaNO 3 + Na 2 O −−−→ Na 3 NO 4
300 C
◦
for 1
3
Density (g/cm ) 1.504 1.405 week
◦
Boiling point ( C) 82.6 120.5
Not surprisingly, the NO 3− ion has been found to have the
◦
Melting point ( C) −41.6 — 4
same tetrahedral geometry as its analog, the PO 3− ion.
Concentration (%) 100 68 by weight 4
3 3
O O
Nitric acid is the most stable and important of the ni-
trogen oxoacids; however, the pure acid decomposes on N P
heating to yield a mixture of oxides, one of which is the O O O O
O O
brown gas NO 2 . A powerful oxidizing agent, HNO 3 reacts
with a host of metals and nonmetals.
Nitrates, the salts of nitric acid, contain the flat, trian- Unlike the stable orthophosphate ion, the orthonitrate
gular nitrate ion: ion is easily destroyed; it readily reacts with the water and
carbon dioxide present in air to yield the nitrate ion:
O
−
−
NO 3− + H 2 O + CO 2 → NO + OH + HCO −
4 3 3
N
O O
VIII. PHOSPHORUS
The most important industrial use of nitric acid is the
preparation of the salt ammonium nitrate, NH 4 NO 3 , which Phosphorus was first isolated in 1699 from urine, not
is used in the manufacture of fertilizers and explosives. In an inappropriate source inasmuch as the element is im-
fact, more than 80% of the nitric acid produced annually portant in numerous bioorganic phosphate compounds as
is devoted to the preparation of fertilizers. well as in typical “inorganic” compounds. Among all el-
Nitrous acid, HNO 2 , is an unstable, weak acid that ements, phosphorus ranks eleventh in order of abundance
is known only in solution. It is prepared by adding a in the lithosphere. Essentially all phosphorus is found
strong acid to a solution containing a nitrite (e.g., NaNO 2 , as orthophosphate (PO ) minerals, the most important
3−
4
KNO 2 ):
of which is apatite, which is written either as Ca 5 (PO 4 ) 3
(OH, F, Cl) or as Ca 3 (PO 4 ) 2 · Ca 2 (PO 4 )(OH, F, Cl). The
+ − + − + −
H + Cl + Na + NO → Na + Cl + HNO 2
2 following idealized equation indicates how elemental
Nitrous acid
phosphorus is currently produced by heating sand and
Nitrite salts are more stable than the parent nitrous acid coke with apatite:
and, like nitrates, are generally soluble in water. Sodium
1400 C
◦
nitrite is the most important nitrite salt, and its use in
2Ca 3 (PO 4 ) 2 + 6SiO 2 + 10C −−−→ 6CaSiO 3
◦
preserving meat (sausage, bacon, etc.) has a long history. 1500 C
Unfortunately, nitrites have been linked to the production + 10CO (g) + P 4 (g)