Sodium is the most common in nature and widely used alkali metal, occupying 11th place in the periodic table (located in the 1st group, the main subgroup, of the 3rd period). When interacting with atmospheric oxygen, it forms Na2O2 peroxide. Is it possible to say that this is the highest sodium oxide ? Of course not, since this substance does not belong to the class of oxides, and its structural formula is written in the following form: Na – O – O – Na. Oxides, in which a chemical element associated with oxygen has a high oxidation state, are called higher oxides. Sodium has only one oxidation state equal to +1. Therefore, the term “higher oxide” does not exist for this chemical element.
Sodium oxide is an inorganic substance, its molecular formula is Na2O. The molar mass is 61.9789 g / mol. The density of sodium oxide is 2.27 g / cm³. In appearance, it is a white solid non-combustible substance that melts at a temperature of plus 1132 ° C, boils at a temperature of plus 1950 ° C and decomposes. When dissolved in water, the oxide reacts violently with it, resulting in the formation of sodium hydroxide, which should be correctly called hydroxide. This can be described by the reaction equation: Na2O + H2O → 2NaOH. The main danger of this chemical compound (Na2O) is that it reacts violently with water, resulting in the formation of aggressive caustic alkali.
Sodium oxide can be obtained by heating the metal to a temperature of no higher than 180 ° C in an environment with a low oxygen content: 4Na + O2 → 2Na2O. In this case, it is not possible to obtain pure oxide, since the reaction products will contain up to 20% peroxide and only 80% of the target substance. There are other ways to produce Na2O. For example, when heating a mixture of peroxide with an excess of metal: Na2O2 + 2Na → 2Na2O. In addition, the oxide is obtained by the reaction of metallic sodium with its hydroxide: 2Na + NaOH → 2Na2O + H2 ↑, as well as by the interaction of a nitrous acid salt with an alkali metal: 6Na + 2NaNO2 → 4Na2O + N2 ↑. All these reactions proceed with an excess of sodium. In addition, when the alkali metal carbonate is heated to 851 ° C, carbon dioxide and oxide of this metal can be obtained according to the reaction equation: Na2CO3 → Na2O + CO2.
Sodium oxide has pronounced basic properties. In addition to reacting violently with water, it also actively interacts with acids and acid oxides. As a result of the reaction with hydrochloric acid, salt and water are formed: Na2O + 2HCl → 2NaCl + H2O. And when interacting with colorless crystals of silicon dioxide, an alkali metal silicate is formed: Na2O + SiO2 → Na2SiO3.
Sodium oxide, as well as oxide of another alkali metal - potassium, does not have much practical value. This substance is usually used as a reagent, is an important component of industrial (soda-lime) and liquid glass, but is not part of optical glasses. As a rule, industrial glass contains about 15% sodium oxide, 70% silica (silicon dioxide) and 9% lime ( calcium oxide ). Na carbonate serves as a flux to lower the temperature at which silicon dioxide melts. Soda glass has a lower melting point than potash-lime or potash-lead. It is the most common, used for the manufacture of window glass and glass containers (bottles and jars) for drinks, food and some other goods. Glassware is often made from tempered sodium-calcium-silicate glass.
Soda-silicate glass is obtained by melting raw materials - Na carbonate, lime, dolomite, silicon dioxide (silica), aluminum oxide (alumina), as well as a small amount of agents (for example, Na sulfate, Na chloride) - in a glass melting furnace at temperatures up to 1675 ° C. Green and brown bottles are obtained from raw materials containing iron oxide. The amount of magnesium oxide and sodium oxide in container glass is less than in glass, which is used for the manufacture of windows.