Nitrogen (nitrogen) has several compounds with Hydrogen (hydrogen), of which ammonia is the most significant. Under laboratory conditions, it is obtained by heating a mixture of ammonium chloride with potassium hydroxide. Until the end of the 19th century, the Chilean deposit of sodium nitrate was considered the only source of Nitrogen compounds. Thanks to scientific developments, chemists have proposed several methods for fixing atmospheric Nitrogen. The first of these was the cyanamide synthesis of ammonia. This method is based on the property of nitrogen to bind to calcium urea. To do this, nitrogen is passed through heated calcium carbide:
N2 + CaC2 = CaCN2 + C
Thus obtained CaCN2 (calcium cyanide) is used as a nitrate fertilizer in agriculture. It should be said that during the treatment of this compound with water vapor, ammonia is formed:
CaCN2 + ZN20 = 2NH3 + CaC03
Ammonia is processed into nitric acid and nitrogen fertilizers. In modern chemistry, another method for producing NH3 is widespread - its synthesis from Nitrogen and Hydrogen:
1/2 N +3/2 H2 = NH3
Thus obtained ammonia is called synthetic. Industrial synthesis of ammonia is carried out in the presence of a catalyst and at a temperature of 500 degrees.
Ammonia is a gas that has a sharp characteristic odor, it is lighter than air. Do not inhale NH3 for a long time, as it is toxic. This gas is quite soluble in H2O. Concentrated aqueous ammonia contains 25% NH3.
When cooled (to -79 ° C), an aqueous solution of ammonia passes into crystalline hydrate. Scientific studies have proved that the bulk of NH3 in aqueous solution resides in the form of hydrated molecules (NH3 · nH2O) and only a small fraction of dissolved ammonia (about 0.5%) interacts with water:
NH3 + H2O = NH4 + + OH -
The alkaline reaction of ammonia solutions is due to the presence of hydroxide ions. Traditionally, ammonia solution is referred to as NH4OH. The alkalinity of the solution is determined by the presence of a hydroxyl group, which is formed as a result of the dissociation of ammonium hydroxide.
The ammonia solution is considered a weak base. In laboratories, sometimes ammonia is obtained by heating ammonia. Ammonia is a fairly active chemical compound that interacts with many substances, while it exhibits only reducing properties.
Ammonia burns in the presence of oxygen with a greenish-yellow flame, oxidizing to free Nitrogen. In the presence of a catalyst (platinum), the oxidation of ammonia goes further until the formation of nitrogen oxide. This reaction is used in the process of producing nitrate acid. It should be said that most of the ammonia obtained in this way is spent on the production of nitrate fertilizers, as well as nitric acid.
During evaporation at -33.4 ° C, liquid NH3 absorbs a lot of heat from the environment and causes cooling. This property is used in refrigeration units to produce artificial ice when storing perishable food products. Often, liquid ammonia is used in the construction of underground structures. The ammonia solution is used in laboratory practice, the chemical industry, household goods, and in medicine.
Ammonia solution application. It is used as a means to stimulate breathing and remove a patient from a fainting state. High concentrations of NH3 can cause respiratory arrest. Sometimes an ammonia solution is used as an emetic (10 drops per 100 ml of water). It should be borne in mind that this pharmaceutical agent cannot be applied externally in the presence of skin diseases (eczema, dermatitis). When poisoning with ammonia vapors, doctors prescribe acetate, citrate, tartrate (tartaric) acid in a 1% concentration. In surgical practice, a solution of ammonia (25 ml / 5 l of boiled, warm water) is used.