Bases are complex compounds that include two main structural components:
- Hydroxy group (one or more). Hence, by the way, the second name of these substances is “hydroxides”.
- Metal atom or ammonium ion (NH4 +).
The name of the bases comes from the combination of the names of both its components: for example, calcium hydroxide, copper hydroxide, silver hydroxide, etc.
The only exception to the general rule of base formation is ammonium hydroxide, when the hydroxo group is attached not to a metal, but to an ammonium cation (NH4 +). This substance is formed when ammonia dissolves in water.
If we talk about the properties of the bases, it should immediately be noted that the valency of the hydroxo group is unity, respectively, the number of these groups in the molecule will directly depend on the valency of the metals involved in the reaction. Examples in this case are the formulas of substances such as NaOH, Al (OH) 3, Ca (OH) 2.
If we talk about the physical properties of the bases, it is worth noting that all of them, without exception, are solids of the most diverse colors. In those cases when the hydroxo group combines with monovalent metals, a water-soluble base is usually formed, in all other cases, the bases obtained as a result of the reaction practically do not dissolve in water. Those that are highly soluble in water are called alkalis. They are chemically hazardous substances that corrode the skin and mucous membranes. In addition to monovalent metals, alkalis also form the so-called alkaline earth metals - for example, such as barium, strontium.
The chemical properties of insoluble bases are that these compounds are either basic or amphoteric hydroxides. The last of them, reacting with acids, behave like alkalis, and vice versa, interacting with alkalis, show signs of acids. The properties of insoluble bases are widely used in light and heavy industries.
The chemical properties of the bases are manifested in their reactions with acids, salts, other bases, as well as in their effect on indicators. In particular, alkalis can be determined by exposing their solution to a specific indicator. In this case, it will noticeably change its color: for example, a litmus test from white will turn blue, and phenolphthalein will become raspberry.
The chemical properties of the bases, manifested in their interaction with acids, lead to the famous neutralization reactions. The essence of this reaction is that the metal atoms, joining the acid residue, form a salt, and the hydroxy group and the hydrogen ion, when combined, turn into water. The neutralization reaction is called this reaction because there is no alkali or acid left after it.
The characteristic chemical properties of the bases are also manifested in their reaction with salts. It should be noted that only alkali react with soluble salts. The structural features of these substances lead to the fact that as a result of the reaction, a new salt and a new, most often insoluble, base are formed.
Finally, the chemical properties of the bases manifest themselves perfectly during thermal exposure to them - heating. Here, carrying out certain experiments, it should be borne in mind that almost all bases, with the exception of alkalis, behave extremely unstable when heated. The vast majority of them almost instantly decompose into the corresponding oxide and water. And if we take the bases of metals such as silver and mercury, then under normal conditions they cannot be obtained, since they begin to decay even at room temperature.