Salt. Ammonium bicarbonate

What is salt?

A class of chemical compounds containing a metal cation or an ammonium cation connected to an anion in the form of an acid residue is collectively referred to as salts. They are divided into normal (or medium), acidic, basic, double, hydrate (crystalline hydrates), complex.

Normal (or medium) salts are characterized by a complete replacement of hydrogen cations in the acid molecule with a metal or ammonium cation, for example: sodium sulfate Na2SO4 or calcium carbonate CaCO3.

If hydrogen cations are partially substituted in the acid molecule, then such salts are called acidic, for example, ammonium hydrogen carbonate NH4HCO3 or sodium hydrogen carbonate NaHCO3.

If a complete and partial substitution of the hydroxyl group for the acid residue occurred in the base molecule, then the salts formed are called basic, for example, copper dihydroxoxycarbonate (CuOH) 2CO3.

In the formula of double salts there are two different cations, for example, aluminum and potassium in alum-alkali alum KAl (SO4) 2 • 12 H2O.

The formula of mixed salts contains two different anions, for example, chlorine lime CaCl (OCl).

The composition of the hydrate salt molecules includes crystallization water, for example, copper sulfate (blue) CuSO4 • 5 H2O.

Molecules of complex salts consist of a complex cation or complex anion, for example, tetraammintsinc (II) chloride [(Zn (NH3) 4)] Cl2.

How are the names of salts formed?

There are two words in the names of salts. The first is the name of the anion, which stands 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, before the name of the anion, the prefix "hydro-" or the prefix "bi-" is written, if one unsubstituted hydrogen cation remains in the molecule. If there are two such hydrogen cations, the prefix "dihydro-" is written before the name of the anion. Examples: bicarbonate (or bicarbonate) of sodium NaHCO3 (this salt is also called baking soda), sodium dihydrogen phosphate NaH2PO4.

Ammonium bicarbonate. Formula

The formula of the acidic salt of carbonic acid NH4HCO3, in which the cation is ammonium, also includes the HCO3- anion, formed by the partial replacement of hydrogen cations in the molecule of this acid with a positively charged ammonium ion. That is, the molecule of this acidic salt consists of one ammonium cation NH4 + bound to one anion that has the name HCO3-. The gross formula for the Hill system is written as: CH5NO3. The molecular weight of the substance is 79.06 a. eat.

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. Gt; Art. (At 25.4 ° C) to 278 mm. Gt; Art. (At 45 ° C).

Ammonium bicarbonate does not dissolve in ethyl alcohol and acetone. It dissolves readily 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, the salt decomposes in aqueous solutions. As a result, ammonia is released, water and carbon dioxide are formed: NH4HCO3 → NH3 ↑ + CO2 ↑ + H2O.

Due to the 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. Receiving

Like all bicarbonates, the acidic ammonium salt can be obtained by prolonged transmission of carbon dioxide through a solution of the average ammonium salt: (NH4) 2CO3 + CO2 + H2O → 2 NH4HCO3.

When the middle salt is slightly heated (30 ° C), its thermal decomposition to acid salt and ammonia occurs: (NH4) 2CO3 → 2 NH4HCO3 + NH3.

If water dissolves carbon dioxide and ammonia, it is also possible to obtain 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 for the production of confectionery and flour products. It is known that sodium bicarbonate NaHCO3 is also used to raise unleaded dough. But its use is less effective, since tightening the kneading or soaking until baking leads to a faster removal of the carbon dioxide formed as a result of the reaction with the acid, and the dough in this case will not be lush and light.

Ammonium bicarbonate is used for dressing skins and when dyeing textile fabrics: during the removal of loose dye (or stripping) a mixture of ammonium salts, including ammonium bicarbonate, is used.

The substance is used in agriculture as a preservative of fodder (decay processes are slowing, thereby increasing safety), as well as fertilizer for potatoes, fodder and vegetable crops. Its properties are used to slow down or stop the processes of nitrification of soils.

Ammonium bicarbonate is used in 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 chemical reagents, for example, ammonium salts.