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 resulting from the interaction of gas molecules and hydrogen protons split off from water. In our article, we will consider its properties and applications in industry, medicine and everyday life.
How ammonium particles are formed
One of the most common types of chemical bonds, characteristic of both inorganic compounds and organic substances, is a covalent bond. It can be formed both by overlapping electron clouds with the opposite type of rotation - spin, and with the help of a donor-acceptor mechanism. In this way, ammonium is formed, the formula of which is NH4+. In this case, the chemical bond is formed using the free orbital of one atomand an electron cloud containing 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 approaching two electron cloud of nitrogen becomes common for it and the H atom. 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 donates an empty electron cell is called an acceptor. The formed bond is called donor-acceptor or coordination, not forgetting that it is a special case of the classical covalent bond. The ammonium ion, whose formula is NH4+, contains four covalent bonds. Of these, three that combine nitrogen and hydrogen atoms are the usual covalent species, and the last is a coordination bond. Nevertheless, all four species are absolutely equivalent to each other. The interaction between water molecules and Cu2+ ions proceeds similarly. In this case, a macromolecule of crystalline copper sulfate is formed.
Ammonium s alts: properties and production
In an addition reaction, the interaction of a hydrogen ion and ammonia leads to the formation of an ion NH4+. The NH3 molecule behaves as an acceptor, therefore it has pronounced base properties. The reaction with inorganic acids leads to the appearance of s alt molecules: chloride, sulfate, ammonium nitrate.
NH3 + HCl=NH4Cl
The process of dissolving ammonia in water also leads to the formation of an ammonium ion, which can be obtained by the equation:
NH3 + H2O=NH4+ + OH-
As a result, the concentration of hydroxyl particles increases in an aqueous solution of ammonia, also called ammonium hydroxide. This leads to the fact that the reaction of the medium becomes alkaline. It can be determined using the indicator - phenolphthalein, which changes its color from colorless to raspberry. Most of the compounds have the form of colorless crystalline substances, readily soluble in water. In many of their manifestations, they resemble s alts of active metals: lithium, sodium, rubidium. The greatest similarities can be found between potassium and ammonium s alts. This is explained by the similar sizes of the radii of potassium ions and NH4+. When heated, they decompose to form ammonia gas.
NH4Cl=NH3 + HCl
The reaction is reversible, since its products can again interact with each other to form an ammonium s alt. When the ammonium chloride solution is heated, the NH3 molecules immediately evaporate, so the smell of ammonia is heard. Therefore, a qualitative reaction to the ammonium ion is the thermal decomposition of its s alts.
Hydrolysis
Ammonia water exhibits the properties of a weak base, therefore s alts containing NH4+ particles undergo an exchange process with water - hydrolysis. Solutions of ammonium chloride or sulfate have a slightly acidic reaction, since in theman excess of hydrogen cations accumulates. If you add alkali to them, for example, sodium hydroxide, then hydroxyl particles will bind hydrogen protons to form water molecules. For example, the hydrolysis of ammonium chloride is an exchange reaction between s alt and water, leading to the formation of a weak electrolyte - NH4OH.
Features of thermal decomposition of ammonium s alts
Most of the compounds of this group, when heated, form gaseous ammonia, the process itself is reversible. However, if the s alt has pronounced oxidizing properties, for example, ammonium nitrate is one of these, then when heated, it irreversibly decomposes to nitrogen monoxide and water. This reaction is a redox reaction, in which the ammonium ion is the reducing agent, and the anion of the acid residue of nitrate acid is the oxidizing agent.
Value of ammonia compounds
Both ammonia gas itself and most of its s alts have a wide range of applications in industry, agriculture, medicine and everyday life. At low pressure (about 7–8 atm.), the gas quickly 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 obtain nitrate acid and its s alts - important mineral fertilizers - nitrate. Ammonium nitrate has a particularly high nitrogen content. It is also used in pyrotechnics and in demolition work for the manufactureexplosives - ammonals. Ammonia, which is ammonium chloride, has found application in galvanic cells, in the production of cotton fabrics, and in metal soldering processes.
The substance in this case accelerates the elimination of oxide films on the metal surface, which are converted into chlorides or restored. 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 s alts in various industries and medicine.
