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ammonia (NH3)
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Chemistry of ammonia
Ammonia reacts with acids to form the ammonium series of salts. It does not burn in air, neither do other substances continue to burn in ammonia. However, in oxygen ammonia burns with a greenish flame.
The nitrogen atom in ammonia has a spare pair of valence electrons with which it can form a bond with an additional hydrogen atom. The resulting ammonium (NH4+) ion behaves chemically like an ion of sodium, though the base ammonium hydroxide (NH4OH) is much weaker than its counterpart sodium hydroxide. This makes it more useful for biological reactions, which generally involve only small energy transfers.
Ammonia can be made on a small scale by mixing together powdered calcium hydroxide (slaked lime) and powdered ammonium chloride, and then heating the dry mixture. Ammonia gas and water vapor are given off leaving calcium chloride behind. The gas is dried by passing it up a tower containing quicklime.
CaCl2 +2H2O + 2NH3
History
Also known as hartshorn or the volatile alkali, ammonia was one of the few substances known to the chemistry of the ancients (see alchemy; being referred to by Pliny under the name of vehement odor, which he evolved by mixing lime with nitrum (probably sal ammoniac – ammonium chloride). It derives its name ammonia from its being obtained from sal ammoniac, which was first procured by heating camels' dung in Libya, near the temple of Jupiter Ammon.
Extraterrestrial ammonia
Ammonia occurs in the atmospheres of gas giant planets and as widely scattered molecules in molecular clouds. The fact that ammonia has similar physical properties to those of water has led to suggestions over the past few decades that ammonia-based life is a possibility.
Related category
• INORGANIC CHEMISTRY
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