Chemical thermodynamics: allowed or prohibited

What is burning? This is the most common oxidation, the connection of fuel with oxygen. But in fact in contact with oxygen are almost all substances, and the reaction does not begin (and thank God). So, it is not enough just reagents, it is necessary to take into account other circumstances. This is what chemical thermodynamics is concerned with.

This science is very simple, and at the same time it is one of the most universal, it can be applied to a myriad of phenomena and processes that occur ... or do not occur. It is here to solve the inflexible laws of this science. The basic concepts of chemical thermodynamics are very simple. And they do not seem to be able to refute, according to Einstein. This unusually gifted scientist believed that this is the most reliable of theories in the universe.

As we know from experience, many of the chemical processes can not go spontaneously. The first researchers noticed that many reactions that begin on their own, occur with the release of heat. However, it was impossible to unambiguously connect the exothermicity of the reaction and its spontaneity. Because there are reactions that begin at high temperatures and go with the absorption of heat, while the reactions also begin spontaneously.

How to understand what is happening? Does nature tend to reduce energy? Everything is more complicated, chemical thermodynamics says that in fact, the environment around us does not like minimum energy, but maximum confusion! Well, some people in this with nature are in solidarity.

Is it possible to describe the disorder strictly? It turns out, it is possible, for this purpose the concept "entropy" is used. Its chemists and physicists are poetically called the "arrow of time". Why? Since processes with increasing entropy spontaneously go only in one direction. And this gives them irreversibility. This is the basis of chemical thermodynamics. You can see the difference from mechanical processes. For example, the movement of balls in the billiards can be scrolled on the video back - and it will look believable. But if you see how rust leaves the nail or Bengal fire recovers , you will immediately realize that this is not true, it does not happen. Of course, this example does not pretend to be absolute, but the increase in entropy really becomes a kind of "time arrow".

Chemical thermodynamics has not developed a device that would determine the level of entropy, it is to a certain extent a speculative concept. But it is possible to calculate it, for this you need to know the change in heat during the reaction and the temperature at which this change occurs. Why is the temperature taken into account? The fact is that the velocity of the particles is very closely related to temperature, and the more these velocities, the more chaos, read, entropy.

The most chaotic form of matter is gas. Therefore, the reaction, in which the amount of gas increases, proceeds with increasing entropy. For example, the decomposition of calcium carbonate. But getting water from oxygen with hydrogen is very difficult, because entropy decreases.

If we calculate the Gibbs energy from the formula , then we can assume whether this reaction will go at a given temperature. However, it will not be possible to find out exactly, perhaps, in order for it to start, it will take a catalyst or a special temperature. The calculations are not useless, they indicate the "permissibility" of a particular reaction. But if chemical thermodynamics shows that the reaction is "forbidden", then there is no point even of tormenting the search for a catalyst - it still will not work.

The science described is closely related to general thermodynamics, which is a branch of physics and explains many processes of various kinds in the world around us. Curious people discover the causes of many phenomena, which for others will always remain a mystery. They say that thermodynamics even proves the existence of God ...