oxides are complex substances composed of two elements, one of which - the oxygen in the second degree of oxidation.
in the chemical literature for the nomenclature of oxides adhere to the following rules:
- When writing formulas oxygen is always put on the second place - NO, CaO.
- Calling oxides, first always use the word oxide, after the genitive is the name of the second element: BaO - barium oxide, K₂O - potassium oxide.
- In case when the element constitutes more oxides after its name in brackets indicate the oxidation state of the element, e.g. N₂O₅ - nitric oxide (V), Fe₂O₃ - iron oxide (II), Fe₂O₃ - iron oxide (III).
- Calling most common oxides, necessarily must be the ratio of atoms in a molecule denoted by the corresponding Greek numerals: N₂O - dinitrogen oxide, NO₂ - nitrogen dioxide, N₂O₅ - dinitrogen pentoxide, NO - nitrogen monoxide.
- anhydrides Inorganic acids advisable to call in the same way as oxides (eg, N₂O₅ - nitric oxide (V)).
oxides can be obtained in several different ways:
- reacts with oxygen simple substances.Simple substances are oxidized under heating often release heat and light.This process is called burning
C + O₂ = CO₂
- Through oxidation of complex substances obtained by oxides of the elements that are included in the composition of the starting material:
2H₂S + 3O₂ = 2 H₂O + 2 SO₂
- decomposition of the nitrates, hydroxides, carbonates:
2Cu (NO₃) ₂ = 2CuO + 4NO₂ + O₂
CaCO₃ = CaO + CO₂
Cu (OH) ₂ = CuO + H₂O
- As a result of the oxidation of metal oxides of other elements.Similar reactions were the basis metallothermy - recovery of metals from their oxides with a more active metal:
2Al + Cr₂O₃ = 2Cr ± Al₂O₃
- by expanding the higher oxides or oxidation of the lower:
4CrO₃ = 2Cr₂O₃ + 3O₃
4FeO + O₂ = 2Fe₂O₃
4CO +O₂ = 2CO₂
Classification of oxides on the basis of their chemical properties mean their division into salt-forming oxides and nesoleobrazuyuschie (indifferent).Salt-forming oxides, in turn, divided into acidic, basic and amphoteric.
basic oxides appropriate base.For example, Na₂O, CaO, MgO - basic oxides, since they correspond to the base - NaOH, Ca (OH) ₂, Mg (OH) ₂.Some oxides (K₂O and CaO) readily react with water to form the corresponding base:
CaO + H₂O = Ca (OH) ₂
K₂O + H₂O = 2KOH
oxides Fe₂O₃, CuO, Ag₂O water do not reactbut neutralize acid, so are considered major:
Fe₂O₃, + 6HCl = 2FeCl₃ + 3H₂OCuO + H₂SO₄ + H₂O
Ag₂O + 2HNO₃ = 2AgNO₃ + H₂O
Typical chemical properties of oxides of this kind - their reaction with acids, which resulted inThey tend to form water and salt:
FeO + 2HCl = FeCl₂ + H₂O
Basic oxides react with acid oxides also:
CaO + CO₂ = CaCO₃.
acid oxides corresponding acid, for example, corresponds to the oxide N₂O₃ nitric acid HNO₂, Cl₂O₇ - perchloric acid HClO₄, SO₃ - sulfuric acid H₂SO₄.
basic chemical properties of oxides is their reaction with a base formed by salt and water:
2NaOH + CO₂ = NaCO₃ + H₂O
Most acidic oxides react with water to form the corresponding acid.At the same time oxide SiO₂ is practically insoluble in water, but it neutralizes the base, therefore, is an acidic oxide:
2NaOH + SiO₂ = (fusion) Na₂siO₃ + H₂O
amphoteric oxides - it oxides, whichDepending on conditions show acidic and basic properties, i.e.by reacting with acids behave as basic metal oxides, and by reaction with bases - as acid.
Not all amphoteric oxides equally interact with bases and acids.Some have more pronounced basic properties, others - acid.
If zinc oxide or chromium equally reacts with acids and bases, then the oxide Fe₂O₃ basic properties predominate.
Properties amphoteric oxides are shown in the example of ZnO:
ZnO + 2HCl = ZnCl₂ + H₂O
ZnO + 2NaOH = Na₂ZnO₂ + H₂O
Nesoleobrazuyuschie oxides do not form either acids or bases (eg, N₂O, NO).
Furthermore, they do not give reactions similar to those salt-forming oxides.Nesoleobrazuyuschie oxides can react with acids or bases, but does not produce products characteristic of salt-forming oxides, such as 150⁰S and 1.5 MPa CO reacts with sodium hydroxide to form a salt - sodium formate:
CO + HCOONa NaOH =
Nesoleobrazuyuschie oxides rasprostranenіy not as wide as other types of oxides are formed and, basically, with the participation of the divalent non-metals.