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Unformatted text preview: N3– ). Most nitrogen compounds are covalent, however nitrogen forms ionic compounds with
certain metals on heating. Li 3 N, Mg 3 N2 , and Ca3 N2 are examples. The nitride ion is a very strong Brønsted
base and readily accepts protons from water, forming ammonia:
Mg3 N2 (s) + 6H 2 O → 3Mg(OH)2 + 2NH 3 Ammonia (NH3 ). The quantity of ammonia produced each year is second in tonnage only to sulfuric acid
production. Ammonia is synthesized by the Haber process, which uses nitrogen gas and hydrogen gas (from
3H2 + N2 → 2NH3
The main use of ammonia is in the production of ammonium and nitrate fertilizers. Ammonia is an important
ingredient in such diverse substances as explosives and nylon.
Liquid ammonia (b.p. –33.4°C) is a solvent resembling water. It undergoes autoionization
2NH3 (l) + – NH4 + NH2
+ – The value of the equilibrium constant at –50°C is K = [NH4 ][NH2 ] = 1 × 10 –33 . Alkali metals dissolve in
liquid ammonia, producing beautiful blue solutions containing a positive ion and an electron.
Li(s) → Li + + e – Back Forward Main Menu TOC Study Guide TOC Textbook Website MHHE Website 4 20 / Nonmetallic Elements and Their Compounds
Both the cation and the electron are highly solvated by ammonia. The solvated electron e– is responsible for the
characteristic color of these solutions. Nitrogen Oxides (N2 O, NO, NO2 ). "Fixed nitrogen" refers to nitrogen present in chemical
compounds. Nitrogen is fixed, that is incorporated into compounds, by the action of lightning in the
atmosphere, by high temperature, by the Haber process, and by certain types of soil bacteria. An appreciable
amount of nitric oxide (NO) is formed in electrical storms and in internal combustion engines.
N2 + O2 → 2NO
Nitric oxide reacts very rapidly with oxygen to yield nitrogen dioxide.
2NO + O 2 → 2NO2
Nitrogen dioxide is a key molecule in the formation of photochemical smog. NO2 is prepared in the laboratory
by the action of concentrated nitric acid on copper.
Cu(s) + 4HNO 3 (aq) → Cu(NO3 )2 (aq) + 2H2 O(l) + 2NO2 (g)
Nitric acid is a major inorganic acid. Over 8.0 million tons were produced in the United States in 1985. Nitric
acid is synthesized by the Ostwald process, which uses ammonia and oxygen as starting materials. Reaction
occurs at 1000°C in the presence of a platinum-rhodium catalyst.
4NH3 (g) + 5O 2 (g) → 4NO(g) + 6H 2 O(g)
Then oxygen is introduced.
2NO(g) + O2 (s) → 2NO2 (s)
The resulting NO2 readily dissolves in water, yielding a mixture of nitrous acid and nitric acid.
2NO2 (g) + H 2 O(l) → HNO2 (aq) + HNO3 (aq)
Then nitrous acid is eliminated by heating.
3HNO2 (aq) → HNO3 (aq) + H2 O(l) + 2NO(g)
Nitric acid is a strong acid, and an oxidizing acid. Aqua regia, the only acid that can dissolve gold, is 1 part
nitric acid and 3 parts hydrochloric acid. Nitric acid is used to manufacture fertilizers and explosives such as
nitroglycerin and TNT.
Nitrous oxide (N2 O) is a colorless gas with a pleasing odor and a sweet taste....
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