What is salt?
The class of chemical compounds, which include a metal cation or ammonium cation, combined with the anion as an acid residue, has a common name - salts. They are divided into normal (or medium), acidic, basic, double, hydrated (crystalline hydrates), complex.
Normal (or medium) salts are characterized by the complete replacement of hydrogen cations in an acid molecule by a metal or ammonium cation, for example: sodium sulfate Na2SO4 or calcium carbonate CaCO3.
If hydrogen cations are partially replaced by a cation in an acid molecule, then such salts are called acidic, for example, ammonium bicarbonate NH4HCO3 or sodium bicarbonate NaHCO3.
If a partial replacement of the hydroxyl group by an acid residue occurred in the base molecule, then the formed salts are called basic, for example, copper dihydroxocarbonate (CuOH) 2CO3.
In the double salt formula, two different cations are present, for example, aluminum and potassium in potassium alum KAl (SO4) 2 • 12 H2O.
The mixed salt formula contains two different anions, for example, CaCl (OCl).
The composition of hydrated salt molecules includes crystallization water, for example, copper sulfate (blue) CuSO4 • 5 H2O.
The molecules of complex salts consist of a complex cation or a complex anion, for example, tetraammine zinc (II) chloride [(Zn (NH3) 4)] Cl2.
How are salt names formed?
In the names of salts there are two words. The first is the name of the anion, which is in the nominative case. The second word (in the genitive case) is derived from the name of the cation. For example: sodium sulfate Na2SO4, iron (II) sulfate FeSO4, iron (III) sulfate Fe2 (SO4) 3, calcium carbonate CaCO3, copper chloride CuCl2. In the name of acid salts, the prefix “hydro-” or the prefix “bi-” is written before the name of the anion if there is one unsubstituted hydrogen cation in the molecule. If there are two such hydrogen cations, then the prefix "dihydro-" is written in front of the name of the anion. Examples: sodium bicarbonate (or bicarbonate) NaHCO3 (this salt is also called baking soda), sodium dihydrogen phosphate NaH2PO4.
Ammonium bicarbonate. Formula
The formula of the acid salt of carbonic acid NH4HCO3, in which ammonium is a cation, also includes the anion HCO3-, formed by the partial replacement of hydrogen cations in the molecule of this acid by a positively charged ammonium ion. That is, the molecule of this acid salt consists of one ammonium cation NH4 + bound to one anion, which is called HCO3- bicarbonate. Hill gross formula is written as: CH5NO3. The molecular weight of the substance is 79.06 a. eat.
The properties
Ammonium bicarbonate is an inorganic compound, in appearance it is colorless crystals with a rhombic lattice. The density is 1.586 g / cm3 (at 20 ° C). Vapor pressure increases: from 59 mm. Hg. Art. (at 25.4 ° C) up to 278 mm. Hg. Art. (at 45 ° C).
Ammonium bicarbonate is not soluble in ethyl alcohol and acetone. It is well soluble in water: with increasing temperature, the solubility of the acid salt increases from 11.9 g / 100 g (at 0 ° C) to 36.6 g / 100 g (at 40 ° C).
Ammonium bicarbonate decomposes with the release of CO2 already at 20 ° C. At a temperature of 36–70 ° C, salt decomposes in aqueous solutions. As a result, ammonia is released, water and carbon dioxide are formed: NH4HCO3 → NH3 ↑ + CO2 ↑ + H2O.
Due to hydrolysis, the aqueous solution has a slightly alkaline reaction. When a concentrated ammonia solution is added, a normal salt is formed: NH4HCO3 + NH3 → (NH4) 2CO3.
Under the action of acids and alkalis, the acid salt is destroyed according to the reaction equations: NH4HCO3 + HCl → NH4Cl + CO2 ↑ + H2O or NH4HCO3 + 2 NaOH → Na2CO3 + NH3 • H2O + H2O.
Ammonium bicarbonate. Getting
Like all bicarbonates, an ammonium acid salt can be obtained by prolonged transmission of carbon dioxide through a solution of a medium ammonium salt: (NH4) 2CO3 + CO2 + H2O → 2 NH4HCO3.
With weak heating (30 ° C) of the middle salt, it decomposes to an acid salt and ammonia: (NH4) 2CO3 → 2 NH4HCO3 + NH3.
If you dissolve carbon dioxide and ammonia in water, you can also get an acidic ammonium salt: NH3 + CO2 + H2O → NH4HCO3.
Application
Ammonium bicarbonate is widely used in the food industry: it plays the role of a chemical baking powder in the manufacture of confectionery and flour products. It is known that sodium bicarbonate NaHCO3 is also used to raise a fresh dough. But its use is less effective, since delaying the batch or holding until baking leads to faster removal of carbon dioxide formed as a result of the reaction with acid, and the dough in this case will not be lush and light.
Ammonium bicarbonate is used for leather dressing and dyeing of textile fabrics: in the process of removing loose dye (or stripping), a mixture of ammonium salts, including ammonium bicarbonate, is used.
The substance is used in agriculture as a feed preservative (rotting processes are slowed down, thereby preserving it), and also as fertilizer for potatoes, fodder and vegetable crops. Its properties are used to slow down or stop the nitrification of soils.
Ammonium bicarbonate is used in the uranium mining, metallurgical industries, as well as in medicine (in the production of vitamins). In organic synthesis, it serves as a raw material for the production of chemicals, for example, ammonium salts.