Each of us was faced with the concepts of a science such as chemistry. Sometimes they are so similar that it is difficult to distinguish one from the other. But it is very important to understand all of them because sometimes such a misunderstanding leads to very stupid situations, and sometimes to unforgivable mistakes. In this article we will tell you what hydrides are, which of them are dangerous and which are not, where they are used and how they are obtained. But let's start with a brief digression into history.
History
Hydrides begin their history with the discovery of hydrogen. Henry Cavendish found this element back in the 18th century . Hydrogen, as you know, is part of the water and is the basis of all other elements of the periodic table. Thanks to him, the existence of organic compounds and life on our planet is possible.
In addition, hydrogen is the basis for many inorganic compounds. Among them are acids and alkalis, as well as unique binary compounds of hydrogen with other elements - hydrides. The date of their first synthesis is not known exactly, but non-metal hydrides have been known to man since ancient times. The most common of these is water. Yes, water is oxygen hydride.
This class also includes ammonia (the main component of ammonia), hydrogen sulfide, hydrogen chloride and the like. We will talk more about the properties of substances from this diverse and amazing class of compounds in the next section.
Physical properties
Hydrides are mostly gases. However, if you take metal hydrides (they are unstable under ordinary conditions and very quickly react with water), then these can also be solid substances. Some of them (for example, hydrogen bromide) exist in the liquid state.
It is simply impossible to give a general characteristic to such a huge class of substances, because they are all different and, depending on the element that is part of the hydride, in addition to hydrogen, have different physical characteristics and chemical properties. But they can be divided into classes, the connections in which are somewhat similar. Below we consider each class separately.
Ionic hydrides are hydrogen compounds with alkali or alkaline earth metals. They are white substances that are stable under normal conditions. When heated, these compounds decompose into their constituent metal and hydrogen without melting. One exception is LiH, which melts without decomposition and, with strong heating, turns into Li and H 2 .
Metal hydrides are transition metal compounds. Very often they have a variable composition. They can be represented as a solid solution of hydrogen in a metal. They also have a crystalline metal structure.
Covalent hydrides include just that species that is most often found on Earth: hydrogen compounds with non-metals. The wide distribution range of these substances is due to their high stability, since covalent bonds are the strongest of chemical ones.
As an example, the formula of silicon hydride: SiH 4 . If we look at it in volume, we will see that hydrogen is very densely attracted to the central silicon atom, and its electrons are displaced to it. Silicon has a sufficiently large electronegativity, so it is able to attract electrons to its core more strongly, thereby reducing the length of the bond between it and the neighboring atom. And as you know, the shorter the connection, the stronger it is.
In the next section, we discuss how hydrides differ from other compounds in terms of chemical activity.
Chemical properties
In this section, it is also worth dividing hydrides into the same groups as in the past. And we begin with the properties of ionic hydrides. Their main difference from the other two species is that they actively interact with water with the formation of alkali and the release of hydrogen in the form of gas. The hydride-water reaction is quite explosive, so the compounds are most often stored without moisture. This is because water, even contained in the air, can initiate a dangerous transformation.
We show the equation of the above reaction using an example of a substance such as potassium hydride:
KH + H 2 O = KOH + H 2
As we can see, everything is quite simple. Therefore, we consider more interesting reactions characteristic of the other two types of substances described by us.
In principle, the remaining transformations that we did not make out are characteristic of all types of substances. They tend to interact with metal oxides to form a metal, either with water or with hydroxide (the latter is characteristic of alkaline and alkaline-earth metals).
Another interesting reaction is thermal decomposition. It occurs at high temperatures and passes until the formation of metal and hydrogen. We will not dwell on this reaction, since we have already analyzed it in the previous sections.
So, we examined the properties of this type of binary compounds. Now it’s worth talking about receiving them.
Getting hydrides
Almost all covalent hydrides are natural compounds. They are stable enough, therefore they do not disintegrate under the influence of external forces. With ionic and metallic hydrides, things are a little more complicated. They do not exist in nature, so they have to be synthesized. This is done very simply: by the reaction of the interaction of hydrogen and the element whose hydride is to be obtained.
Application
Some hydrides do not have a specific application, but most are very important substances for industry. We will not go into details, because everyone has heard that, for example, ammonia is used in many fields and serves as an indispensable substance for the production of artificial amino acids and organic compounds. The use of many hydrides is limited by their chemical properties. Therefore, they are used exclusively in laboratory experiments.
Application is too extensive a section for this class of substances, so we limited ourselves to general facts. In the next part we will tell you how many of us, without proper knowledge, confuse harmless (or at least known) substances with each other.
Some misconceptions
For example, some believe that hydrogen hydride is something dangerous. If this substance can be called so, then no one does. If you think about it, then hydrogen hydride is a compound of hydrogen with hydrogen, and therefore - an H 2 molecule. Of course, this gas is dangerous, but only in a mixture with oxygen. In its pure form, it is not dangerous.
There are many obscure names. They terrify an unusual person. However, as practice shows, most of them are harmless and are used for domestic purposes.
Conclusion
The world of chemistry is huge, and we think that if not after this, then after several other articles you will see for yourself. That is why it makes sense to dive into his study with his head. Mankind has discovered many new things, and remains unknown even more. And if it seems to you that there is nothing interesting in the field of hydrides, you are greatly mistaken.