Many oxides can react with water to produce acid.For example:
SO3 + H2O = H2SO4 (sulfuric acid is formed).
SiO2 + 2KOH = K2SiO3 + H2O (water-insoluble silica is reacted with potassium hydroxide.
basic oxides, in contrast, react with acids, also forming a salt and water. Those ofthem, are soluble in water and react with it, forming a base. Exemplary:
ZnO + 2HCl = ZnCl2 + H2O (water-insoluble zinc oxide reacts with hydrochloric acid).
Na2O + H2O = 2NaOH
should remember that the valence of oxygen in the oxide is always equal to 2. Accordingly, when drawing up the formula necessary to know only the valence of the second element. For example: alkali metals of the first group - mo
novalent. Therefore, oxides of the general formula would look like this: El2O. Ie., Li2O, Na2O, K2O, Rb2O. (E - "Element»).
Alkaline earth metals of the second group - bivalent.The general formula oxides - ELO.And it will look: BeO, MgO, CaO, SrO.
amphoteric elements of the third group, respectively, the trivalent.The general formula oxides - El2O3.A typical example - already mentioned aluminum oxide Al2O3.
elements of the fourth group exhibit or more acidic properties (carbon, silicon), or the more basic (germanium, tin, lead).In any case, the general formula - ElO2 (CO2, SiO2).
general formula of the fifth group - El2O5.Example - higher oxides of nitrogen, N2O5, from which the nitric acid.Or higher vanadium oxide V2O5 (vanadium though - metal, its highest oxide exhibits acidic properties).
Accordingly, the sixth group of the formula where the oxygen itself - ElO3.Higher oxides - SO3, SrO3, WO3.Note that while chromium and tungsten - metals, their higher oxides by analogy with vanadium oxide also exhibit acidic properties.
should be clarified that only indicates the higher oxides of the elements.For example, in addition to chromium oxide CrO3, chromium shestivalenten where there oxide Cr2O3, wherein this element has a valence of 3. In addition to nitrogen oxide N2O5, there oxide N2O, NO, NO2.Such examples are many.Therefore, when writing the formula oxide, check what is the valence of the connection element connected to the oxygen!