In chemical compounds, NH4 + manifests itself as a positive singly charged alkali metal cation. When interacting with acidic anions, substances with a crystalline structure are formed - ammonium salts: NH4N03 nitrate , NH4C1 chloride, (NH4) 2S04 sulfate, which consist of an acid anion and an ammonium group.
Ammonium salts are obtained during the neutralization reaction, which is carried out in the process of the interaction of ammonia with acids.
Ammonium salts, like, in principle, most alkali metals, can dissociate (split into cations and anions) in aqueous solutions into ions: ammonium salts, like alkali metal salts, dissociate into ions:
NH4N03 ↔ NH4 ++ NO3-
During heating, dry ammonium salts decompose into ammonia and acid; this process is also called thermal dissociation.
The resulting acid (for example, hydrochloric acid) evaporates with NH3, and when cooled it combines with ammonia to form a salt. It should be said that a reversible decomposition process is also possible:
NH3 + HCl ↔ NH4Cl
Thus, when heated, ammonia is sublimated, however, after some time, a white coating of ammonium chloride again appears on the upper parts of the tube. As a result of salt formation by a non-volatile acid, for example, (NH4) 2S04, only NH3 escapes during heating, and the acid remains. Such a process is called irreversible decomposition.
All ammonium salts are well decomposed by alkalis (when heated) with the release of ammonia:
NH4 + + OH -↔NH3 ↑ + H20
This reaction is used to recognize mineral fertilizers with an ammonium form of nitrogen.
During the interaction of ammonium carbonate with mineral and organic acids , carbon dioxide is released. The interaction of ammonium sulfate or chloride with AgNO3 or BaCl gives rise to characteristic white precipitates.
Ammonium salts: examples
Ammonium salts widely used in agriculture. It is an excellent material for mineral nutrition of plants (for example, ammonium sulfate - (NH4) 2S04). As you know, nitrogen plants can be absorbed only in bound form (NO3, NH4). Therefore, nitrogenous compounds are very effective. Of great importance is ammonium nitrate, which contains ammonium NH4 nitrate NO3-nitrogen.
Ammonium dihydrogen phosphate and hydrogen phosphate, known as ammophos NH4H2P04 and diammophos (NH4) 2HP04, contain two chemical elements of plant nutrition - nitrogen and phosphorus. Ammonium salts are part of fertilizer mixtures.
In the interaction of ammonia with carbon monoxide (IV), urea or urea NH2 – CO – NH2 is synthesized.
Ammonium chloride (NH4C1) or ammonia is used in galvanic cells, during dyeing and sieve printing, tinning and soldering. Contacting with heated metal, ammonia decomposes into hydrogen chloride and ammonia. Hydrochloric acid interacts with an oxide that pollutes the surface of the metal, and a volatile salt forms.
It should be noted that solder adheres very well to a cleaned surface. NH4NO3 (ammonium nitrate) together with coal and aluminum salts are an integral part of the explosive - ammonal. These compounds are used in the development of rocks. Ammonium bicarbonate (NH43) is very often used in the food and confectionery industry. This compound is also used as a preservative for various types of feed. NH4HCO3 has denitrifying properties, which helps to accelerate the ripening of the crop.
Qualitative reaction to ammonium salts. When a solution of ammonium salts with alkalis is heated, ammonium hydroxide is formed, which breaks down with the release of ammonia.
The presence of ammonia can be judged by the specific smell, as well as using colored paper indicators. To carry out this reaction, it is necessary to take 1.0 cm3 of a solution of ammonium salt, add 0.5 cm3 of a solution of sodium hydroxide and heat. During heating, ammonia is released, a characteristic odor is formed, the red litmus turns blue.