Ammonia is a gas with excellent solubility in water: up to 700 liters of a gaseous compound can be dissolved in one liter of it. As a result, not only ammonia hydrate is formed, but also particles of hydroxyl groups, as well as ammonium. This is an ion arising from the interaction of gas molecules and hydrogen protons, which are split off from water. In our article we will consider its properties and applications in industry, medicine and everyday life.
How are ammonium particles formed?
One of the most common types of chemical bonds characteristic of both inorganic compounds and organic substances is the covalent bond. It can be formed both by overlapping electron clouds having the opposite form of rotation - spin, and by using a donor-acceptor mechanism. In this way, ammonium is formed, the formula of which is NH 4 + . In this case, a chemical bond is formed using the free orbital of one atom and an electron cloud, including two electrons. Nitrogen provides the ion with its own pair of negative particles, and the hydrogen proton has a free 1s orbital. At the moment of convergence of the two, the electron cloud of nitrogen becomes common for her and the atom H. This structure is called the molecular electron cloud, in which the fourth covalent bond is formed.
Donor-acceptor mechanism
A particle that provides a pair of electrons is called a donor, and a neutral atom that gives away an empty electron cell is called an acceptor. An educated bond is called a donor-acceptor or coordination bond, not forgetting that it is a special case of classical covalent bond. The ammonium ion, whose formula is NH 4 + , contains four covalent bonds. Of these, three, combining nitrogen and hydrogen atoms, are an ordinary covalent species, and the latter is a coordination bond. Nevertheless, all four species are absolutely equivalent to each other. Similarly, there is an interaction between water molecules and Cu 2+ ions . In this case, a macromolecule of copper sulfate crystalline hydrate is formed.
Ammonium salts: properties and preparation
In the addition reaction, the interaction of a hydrogen ion and ammonia leads to the formation of an NH 4 + ion. The NH 3 molecule behaves as an acceptor; therefore, it has pronounced base properties. The reaction with inorganic acids leads to the appearance of salt molecules: chloride, sulfate, ammonium nitrate.
NH 3 + HCl = NH 4 Cl
The process of dissolving ammonia in water also leads to the formation of an ammonium ion, the receipt of which can be expressed by the equation:
NH 3 + H 2 O = NH 4 + + OH -
As a result, in an aqueous solution of ammonia, also called ammonium hydroxide, the concentration of hydroxyl particles increases. This leads to the fact that the reaction of the medium becomes alkaline. It can be determined using the indicator - phenolphthalein, which changes color from colorless to raspberry. Most of the compounds have the form of colorless crystalline substances, readily soluble in water. In many of its manifestations, they resemble salts of active metals: lithium, sodium, rubidium. The greatest similarities can be found between the potassium and ammonium salts. This is explained by the close radii of potassium ions and NH 4 + . When heated, they decompose, forming gaseous ammonia.
NH4Cl = NH3 + HCl
The reaction is reversible, since its products can again interact with each other with the formation of an ammonium salt. When heated, a solution of ammonium chloride, NH 3 molecules immediately evaporate, so the smell of ammonia is heard. Therefore, a qualitative reaction to an ammonium ion is the thermal decomposition of its salts.
Hydrolysis
Ammonia water exhibits the properties of a weak base, so salts containing NH 4 + particles undergo a process of exchange with water - hydrolysis. Solutions of ammonium chloride or sulfate have a slightly acidic reaction, since an excess amount of hydrogen cations accumulates in them. If you add alkali to them, for example, sodium hydroxide, then the hydroxyl particles will bind hydrogen protons to form water molecules. For example, the hydrolysis of ammonium chloride is an exchange reaction between salt and water, leading to the formation of a weak electrolyte - NH4OH.
Features of thermal decomposition of ammonium salts
Most of the compounds of this group form gaseous ammonia upon heating; the process itself is reversible. However, if the salt has pronounced oxidizing properties, for example, ammonium nitrate belongs to these, then when it is heated, it irreversibly decomposes to nitrogen monoxide and water. This reaction is a redox reaction in which an ammonium ion is a reducing agent and an anion of an acidic nitrate residue is an oxidizing agent.
The value of ammonia compounds
Both gaseous ammonia and most of its salts have a wide range of applications in industry, agriculture, in medicine and in everyday life. At low pressure (about 7–8 atm.), The gas rapidly liquefies, absorbing a large amount of heat. Therefore, it is used in refrigeration units. In chemical laboratories, ammonium hydroxide is used as a weak volatile base convenient for experiments. Most of the ammonia is used to produce nitrate acid and its salt - an important mineral fertilizer - nitrate. Ammonium nitrate has a particularly high nitrogen content. It is also used in pyrotechnics and in subversive works for the manufacture of explosives - ammonals. Ammonium chloride, which is ammonium chloride, has found application in galvanic cells, in the production of cotton fabrics, in metal soldering processes.
The substance in this case accelerates the elimination of oxide films on a metal surface, which are converted to chlorides or reduced. In medicine, ammonia, which has a pungent odor, is used as a means of restoring consciousness after a patient faints.
In our article, we examined the properties and application of ammonium hydroxide and its salts in various industries and medicine.