Properties of Ammonia

Ammonia is lighter than air (density of 0.771 g/l at 1 atm and 20°C). It is easily liquefied and the liquid boils at -33.35 °C, and freezes at -77.7 °C to a mass of white crystals. Liquid ammonia has a high specific heat capacity and a high refractíon index.

Liquid ammonia is similar to water in its physical properties, because in liquid ammonia the molecules are strongly associated (as in water). Liquid ammonia is the best-known and most widely studied non-aqueous ionizing solvent. Its most conspicuous property is its ability to dissolve alkali metals to form highly coloured, electrically conducting solutions containing solvated electrons. Apart from these remarkable solutions, much of the chemistry in liquid ammonia can be classified by analogy with related reactions in aqueous solutions. Comparison of the physical properties of NH₃ with those of water shows that NH₃ has the lower mp, bp, density, viscosity, dielectric constant and electrical conductivity; this is due at least in part to the weaker H bonding in NH₃ and the fact that such bonding cannot form cross-linked networks since each NH₃ molecule has only 1 lone-pair of electrons compared with 2 for each H₂O molecule.