The smell of this gas is known to everyone - you can immediately feel it if you open a jar of ammonia. Something about its properties was told to us at school. It is also known that it is one of the key products of the chemical industry: it is in it that it is easiest to turn nitrogen, which does not like to enter into chemical reactions. Ammonia is the first point from which the production of many nitrogen-containing compounds begins: various nitrites and nitrates, explosives and aniline dyes, medicines and polymeric materials ...
Quick reference
The name of this substance comes from the Greek "hals ammoniakos", which means ammonia. The ammonia molecule is a kind of pyramid with a nitrogen atom at the top and three hydrogen atoms at the base. The formula of this compound is NH3. Under normal conditions, ammonia is a colorless gas with a suffocating pungent odor. Its density at -33.35 ° C (boiling point) is 0.681 g / cm
3 . And this substance melts at -77.7 ° C. The molar mass of ammonia is 17 grams per mole. A pressure of 0.9 MPa causes ammonia to compress at room temperature. Get it in industry under pressure using catalytic synthesis from hydrogen and
oxygen. Liquid ammonia is a highly concentrated fertilizer, refrigerant. Caution should be exercised with this substance, as it is toxic and explosive.
Curious facts
Liquid ammonia has rather unusual properties. Outwardly, it resembles plain water. Like H 2 O, it perfectly dissolves many organic and inorganic compounds. Most salts in it dissociate upon dissolution into ions. At the same time, chemical reactions, unlike water, occur in it in a completely different way.
| ZnCl 2 | Bacl 2 | Kcl | NaCl | Ki | Ba (NO3) 2 | Agi |
Solubility at 20 ° C per 100 g of solvent | ammonia | 0 | 0 | 0.04 | 3 | 182 | 97 | 207 |
water | 367 | 36 | 34 | 36 | 144 | nine | 0 |
The data in this table lead to the idea that liquid ammonia is a unique medium for carrying out some metabolic reactions, which are practically impossible in aqueous solutions.
For instance:
2AgCl + Ba (NO 3 ) 2 = 2AgNO 3 + BaCl 2 .
Since NH 3 is a strong proton acceptor, acetic acid, despite being considered weak, dissociates completely, just as strong acids do. Of most interest are solutions in liquid ammonia of alkali metals. As early as 1864, chemists noticed that if you give them some time, ammonia will evaporate, and pure metal will be in the sediment. Almost the same thing happens with aqueous solutions of salts. The difference is that alkali metals, although in small quantities, nevertheless react with ammonia, resulting in the formation of salt-like amides:
2Na + 2NH 3 = 2NaNH 2 + H 2 .
The latter are quite stable substances, but when in contact with water they decompose immediately:
NaNH2 + H 2 O = NH 3 + NaOH.
When studying the properties of liquid ammonia, chemists noticed that when a metal is dissolved in it, the volume of the solution becomes larger. Moreover, its density is reduced. This is another difference between the considered solvent and ordinary water. It's hard to believe, but a concentrated and dilute solution of any alkali metal in liquid ammonia does not mix with each other, despite the fact that the metal in both of them is the same! Thanks to experiments, new surprising facts are constantly being discovered. So, it turned out that the sodium
solution frozen in liquid
ammonia has a very low resistance, which means that NH
3 can be used to obtain a superconducting system. It is not surprising that this gas and its solutions are still of interest to the minds of both physicists and chemists.