Oxides. Sodium-forming and non-salt-forming oxides

Oxides are complex substances consisting of two elements, of which one is oxygen in the second oxidation state.

In the chemical literature for the nomenclature of oxides adhere to the following rules:

1. When writing formulas, oxygen is always put on the second place - NO, CaO.
2. Naming oxides, first always use the word oxide, after it in the genitive case the name of the second element goes: BaO - barium oxide, K₂O - potassium oxide.
3. In the case where the element forms several oxides, after its name, the degree of oxidation of this element is indicated in parentheses, for example N₂O₅ - nitric oxide (V), Fe₂O₃ - iron oxide (II), Fe₂O₃ - iron (III) oxide.
4. Calling the most common oxides, it is necessary to designate the ratio of atoms in the molecule to the corresponding Greek numerals: N₂O - dinitrogen oxide, NO₂ - nitrogen dioxide, N₂O₅ - dinitrogen pentoxide, NO - nitrogen monoxide.
5. Anhydrides of inorganic acids are desirably called just like oxides (for example, N₂O₅ - nitrogen oxide (V)).

Oxides can be obtained in several different ways:

1. Interaction with oxygen of simple substances. Simple substances are oxidized when heated, often with the release of heat and light. This process is called combustion
   C + O₂ = CO₂
2. Due to the oxidation of complex substances, oxides of elements are obtained, which are included in the starting material:
   2H₂S + 3O₂ = 2 H₂O + 2 SO₂
3. The decomposition of nitrates, hydroxides, carbonates:
   2Cu (NO₃) ₂ = 2CuO + 4NO₂ + O₂
   CaCO₃ = CaO + CO₂
   Cu (OH) ₂ = CuO + H₂O
4. As a result of the oxidation of metals by oxides of other elements. Such reactions became the basis of metallothermy - the reduction of metals from their oxides with the help of more active metals:
   2Al + Cr₂O₃ = 2Cr ± Al₂O₃
5. By decomposition of higher oxides or by oxidation of lower oxides :
   4CrO₃ = 2Cr₂O₃ + 3O₃
   4FeO + O₂ = 2Fe₂O₃
   4CO + O₂ = 2CO₂

Classification of oxides on the basis of their chemical properties implies their division into salt-forming and non-salt-forming oxides (indifferent). Salt-forming oxides, in turn, are divided into acid, basic and amphoteric.

The base oxides correspond to the bases. For example, Na₂O, CaO, MgO are basic oxides, since they correspond to the bases - NaOH, Ca (OH) ₂, Mg (OH) . Some oxides (K₂O and CaO) easily react with water and form the corresponding bases:

CaO + H₂O = Ca (OH) ₂

K₂O + H₂O = 2KOH

Oxides Fe₂O₃, CuO, Ag₂O do not react with water, but neutralize acids, due to which they are considered as the main:

Fe₂O₃, + 6HCl = 2FeCl₃ + 3H₂OCuO + H₂SO₄ + H₂O

Ag₂O + 2HNO₃ = 2AgNO₃ + H₂O

Typical chemical properties of oxides of this kind are their reaction with acids, as a result of which, as a rule, water and salt are formed:

FeO + 2HCl = FeCl₂ + H₂O

The basic oxides also react with acidic oxides:

CaO + CO₂ = CaCO.

Acidic acids correspond to acids. For example, N₂O окси oxide corresponds to nitric acid HNO₂, Cl₂O₇ - perchloric acid HClO₄, SO₃ - sulfuric acid H₂SO.

The main chemical property of such oxides is their reaction with bases, salt and water are formed:

2NaOH + CO₂ = NaCO₃ + H₂O

Most acidic oxides react with water to form the corresponding acids. At the same time, SiO окси oxide is practically insoluble in water, however it neutralizes the bases, hence it is an acid oxide:

2NaOH + SiO₂ = (fusion) Na₂siO₃ + H₂O

Amphoteric oxides are oxides that, depending on the conditions, exhibit acidic and basic properties, i. E. When interacting with acids, behave like basic oxides, and when interacting with bases they behave like acidic ones.

Not all amphoteric oxides interact to the same degree with bases and acids. Some have more basic properties, others have acidic properties.

If zinc oxide or chromium reacts to the same degree with acids and bases, then the basic properties of Fe₂O окси oxide predominate.

The properties of amphoteric oxides are illustrated by the example of ZnO:

ZnO + 2HCl = ZnCl₂ + H₂O

ZnO + 2NaOH = Na₂ZnO₂ + H₂O

Non-forming oxides do not form acids or bases (for example, N₂O, NO).

In addition, they do not give the reactions characteristic of salt-forming oxides. Non-forming oxides can react with acids or alkalis, but no products characteristic of salt-forming oxides are formed, for example at 150 ° C and 1.5 MPa CO reacts with sodium hydroxide to form sodium formate:

CO + NaOH = HCOONa

Nonsoluble oxide oxides are not widely distributed as other types of oxides and are formed, mainly, with the participation of divalent non-metals.