No process in the world is possible without the intervention of chemical compounds, which, reacting with each other, create the basis for favorable conditions. All elements and substances in chemistry are classified according to the structure and functions that they perform. The main ones are acids and bases. During their interaction, soluble and insoluble salts are formed.
Examples of acids, salts
An acid is a complex substance that contains one or more hydrogen atoms and an acid residue in its composition. A distinctive property of such compounds is the ability to replace hydrogen with a metal or some positive ion, resulting in the formation of the corresponding salt. Almost all acids, with the exception of some (H 2 SiO 3 - silicic acid), are soluble in water, and strong ones, such as HCl (hydrochloric), HNO 3 (nitric), H 2 SO 4 (sulfuric), completely decompose into ions. And weak (for example, HNO 2 - nitrogenous, H 2 SO 3 - sulfur) - partially. Their pH (pH), which determines the activity of hydrogen ions in solution, is less than 7.
Salt is a complex substance, most often consisting of a metal cation and an anion of an acid residue. Usually it is obtained by reacting acids and bases. As a result of this interaction, water is still released. As cations, salts can serve, for example, NH 4 + cations. They, like acids, can dissolve in water with varying degrees of solubility.
Examples of salts in chemistry: CaCO 3 - calcium carbonate, NaCl - sodium chloride, NH 4 Cl - ammonium chloride, K 2 SO 4 - potassium sulfate and others.
Salt classification
The following categories of salts are distinguished depending on the amount of substitution of hydrogen cations:
- Medium - salts in which the hydrogen cations are completely replaced by metal cations or other ions. Such examples of salts in chemistry can serve as the most common substances that are found most often - KCl, K 3 PO 4 .
- Acidic - substances in which hydrogen cations are not completely replaced by other ions. Examples are sodium bicarbonate (NaHCO 3) and potassium hydrogen phosphate (K 2 HPO 4 ).
- The main ones are salts in which acid residues are not completely replaced by a hydroxy group with an excess of base or lack of acid. These substances include MgOHCl.
- Complex salts: Na [Al (OH) 4 ], K 2 [Zn (OH) 4 ].
Depending on the amount of cations and anions present in the salt, there are:
- Simple - salts containing one type of cation and anion. Examples of salts: NaCl, K 2 CO 3 , Mg (NO3) 2 .
- Double - salts, which consist of a pair of types of positively charged ions. These include aluminum-potassium sulfate.
- Mixed - salts in which there are two types of anion. Examples of salts: Ca (OCl) Cl.
Salt production
These substances are obtained mainly by the reaction of alkali with acid, resulting in the formation of water: LiOH + HCl = LiCl + H 2 O.
In the interaction of acidic and basic oxides, salts are also formed: CaO + SO 3 = CaSO 4.
They are obtained when the acid and metal enter the reaction, which is up to hydrogen in the electrochemical series of voltages. Typically, this is accompanied by gas evolution: H 2 SO 4 + Li = Li 2 SO 4 + H 2.
In the interaction of bases (acids) with acid (basic) oxides, the corresponding salts are formed: 2KOH + SO 2 = K 2 SO 3 + H 2 O; 2HCl + CaO = CaCl 2 + H 2 O.
Basic salt reactions
In the interaction of the salt and the acid, another salt and a new acid are obtained (the condition for such a reaction is that a precipitate or gas should result): HCl + AgNO 3 = HNO 3 + AgCl.
When two different soluble salts are reacted, one obtains: CaCl 2 + Na 2 CO 3 = CaCO 3 + 2NaCl.
Some salts which are poorly soluble in water have the ability to decompose into the corresponding reaction products when heated: CaCO 3 = CaO + CO 2.
Some salts may undergo hydrolysis: reversible (if it is a salt of a strong base and a weak acid (CaCO 3 ) or a strong acid and a weak base (CuCl 2 )) and irreversibly (a salt of a weak acid and a weak base (Ag 2 S)). Salts of strong bases and strong acids (KCl) do not hydrolyze.
They can also dissociate into ions: partially or completely, depending on the composition.