Oxides are substances in which molecules consist of an oxygen atom with an oxidation state of 2 and atoms of some other element.
Oxides are formed directly through the interaction of oxygen with another substance or indirectly through the decomposition of bases, salts, acids. This type of compound is very common in nature, and can exist in the form of a gas, liquid or solid. Oxides are also found in the earth's crust. So, sand, rust, carbon dioxide and even ordinary water are all examples of oxides.
There are both salt-forming and non-salt-forming oxides. Salt forming as a result of a chemical reaction gives salts. These include non-metal and metal oxides, which form an acid in a reaction with water, and normal and acid salts in a reaction with a base. For salt forming, for example, copper oxide.
Accordingly, it is impossible to obtain salt from non-salt forming ones. Examples include carbon dioxide, diazot oxide, and nitric oxide.
Salt-forming oxides are divided, in turn, into basic, acidic and amphoteric. Let's talk more about the main ones.
So, basic oxides are the oxides of certain metals, corresponding to which hydroxides belong to the class of bases. That is, when interacting with acid, such substances form water and salt. For example, these are K2O, CaO, MgO, etc. Under ordinary conditions, the main oxides are solid crystalline formations. The degree of metal oxidation in such compounds, as a rule, does not exceed +2 or rarely +3.
Chemical properties of basic oxides
1. Reaction with acid
It is in the reaction with the acid that the oxide exhibits its basic properties, so a type of oxide can be proved by such an experiment. If salt and water are formed, then this is the main oxide. Acid oxides in this interaction form acid. And amphoteric ones can exhibit either acidic or basic properties - it depends on the conditions. These are the main differences between non-salt-forming oxides among themselves.
2. Reaction with water
The oxides that are formed by metals from the electrotechnical series of stresses facing magnesium enter into interaction with water. Upon reaction with water, they form soluble bases. This is a group of oxides of alkaline earth and alkali metals (barium oxide, lithium oxide, etc.). Acid oxides in water form acid, while amphoteric oxides do not react to water.
3. Reaction with amphoteric and acid oxides
The oxides, which are opposite in their chemical nature, react with each other, forming salts. For example, basic oxides can interact with acidic ones, but do not react to other representatives of their group. The most active are the oxides of alkali metals, alkaline earth and magnesium. Even under ordinary conditions, they are fused with solid amphoteric oxides, with solid and gaseous acidic. Upon reaction with acid oxides, they form the corresponding salts.
But the basic oxides of other metals are less active and practically do not react with gaseous (acidic) oxides. They can only enter into an addition reaction by fusion with solid acid oxides.
4. Redox properties
Oxides of active alkali metals do not exhibit pronounced reducing or oxidizing properties. And, on the contrary, oxides of not so active metals can be reduced by coal, hydrogen, ammonia or carbon monoxide.
Preparation of basic oxides
1. Hydroxide decomposition: when heated, insoluble bases decompose into water and basic oxide.
2. Oxidation of metals: an alkali metal, when burned in oxygen, forms peroxide, which then forms a basic oxide upon reduction.