Chemical properties of bases
The bases are complex compounds, which include two basic structural components:
- Hydroxy group (one or more). Hence, by the way, the second name of these substances is "hydroxides".
- A metal atom or an ammonium ion (NH4 +).
The name of the bases comes from a combination of the names of both its components: for example, calcium hydroxide, copper hydroxide, silver hydroxide, etc.
The only exception to the general ruleThe formation of bases should be considered as ammonium hydroxide, when the hydroxo group is attached to the ammonium cation (NH4 +), not to the metal, but to the metal. This substance is formed when there is a dissolution of ammonia in the water.
If we talk about the properties of the bases, then immediatelyit should be noted that the valence of the hydroxo group is unity, respectively, the number of these groups in the molecule will depend directly on the valency of the reacting metals. Examples in this case are the formulas of such substances as NaOH, Al (OH) 3, Ca (OH) 2.
If we talk about physical propertiesit is worth noting that all of them, without exception, are solids of the most diverse color. In cases where the hydroxo group is combined with monovalent metals, a base that is well soluble in water is usually formed, in all other cases, the bases obtained in the reaction are practically insoluble in water. Those of them that are soluble in water are called alkalis. They are chemically dangerous substances that damage the skin and mucous membranes. In addition to monovalent metals, alkalis also form the so-called alkaline earth metals - for example, such as barium and strontium.
Chemical properties of insoluble basesconsist in the fact that these compounds are either basic or amphoteric hydroxides. The last of them, reacting with acids, behave like alkalis, and conversely, interacting with alkalis, show signs of acids. Properties of insoluble bases are widely used in light and heavy industries.
The chemical properties of the bases are manifested in theirreactions with acids, salts, other bases, and also in their action on indicators. In particular, alkalis can be determined if their solution is influenced by a certain indicator. In this case, it will noticeably change its color: for example, a litmus paper made of white becomes blue, and phenolphthalein - crimson.
The chemical properties of bases, manifested in theirinteraction 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 hydroxo group and the hydrogen ion, when combined, turn into water. By reaction of neutralization this reaction is called because after it there is no alkali or acid left.
Characteristic chemical properties of basesare also manifested in their reaction with salts. It should be noted that only alkalis react with soluble salts. The peculiarities of the structure of these substances lead to the fact that as a result of the reaction a new salt is formed and a new, most often insoluble, base.
Finally, the chemical properties of the bases are beautifulmanifest themselves during the thermal impact on them - heating. Here, carrying out these or those experiments, it is worth bearing in mind that practically all the bases, with the exception of alkalis, behave extremely unstably when heated. The overwhelming majority almost instantly breaks up into the corresponding oxide and water. And if you take the foundations of metals such as silver and mercury, then under normal conditions they can not be obtained, since they begin to disintegrate already at room temperature.