Chemical equilibrium is the basis of reversible chemical reactions

According to one of the classifications used to describe chemical processes, there are two types of opposite reactions - reversible and Irreversible. Reversible reaction does not reach the end, i.e. None of the substances that entered it, is not consumed completely and does not change the concentration. Such a process ends with the establishment of a balance or chemical equilibrium, which is denoted by ⇌. But the direct and reverse reactions go on and on, without stopping, therefore the balance is called dynamic or mobile. The onset of chemical equilibrium indicates that the direct reaction occurs at the same speed (V1) as the inverse (V2), V1 = V2. If the pressure and temperature are unchanged, then the equilibrium in this system can last indefinitely.

Quantitatively, the chemical equilibrium is described by the equilibrium constant, which is equal to the ratio of the constants of the straight line (K1) and the reverse (K2) reactions. You can calculate it using the formula: K = K1 / K2. The equilibrium constant will depend on the composition of the reactants and the temperature.
The displacement of the chemical equilibrium occurs according to the Le Chatelier principle, which reads: "If the external system influences a system that is in equilibrium, then the equilibrium will be violated and shifted in the direction opposite to the given change."

Consider Chemical equilibrium and the conditions of its displacement by the example of the formation of an ammonia molecule: N2 + 3H2 ↔ 2NH3 + Q.

Considering the equation of this reaction, we establish:

1. A direct reaction is a compound reaction, because Of 2 simple substances, 1 complex (ammonia) is formed, and the reverse is decomposition;

2. The direct reaction proceeds with the formation of heat, therefore it is exothermic, hence, the inverse is endothermic and proceeds with absorption of heat.

Now we consider this equation under the condition of modification of certain parameters:

1. Change in concentration. If we increase the concentration of the initial substances - nitrogen and hydrogen - and reduce the amount of ammonia, then the equilibrium will shift to the right to form NH3. If you want to move it to the left, increase the concentration of ammonia.

2. The increase in temperature will shift the equilibrium towards the reaction, at which heat is absorbed, and when it is lowered, it is released. Therefore, if the temperature is increased in the synthesis of ammonia, then the equilibrium shifts towards the initial products, i.e. Left, and with a drop in temperature - to the right, towards the reaction product.

3. If you increase the pressure, then the equilibrium shifts to the side, where the amount of gaseous substances is less, and when pressure decreases - to the side where the amount of gases increases. When NH3 is synthesized from 4 mols of N2 and 3H2, 2 NH3 are obtained. Therefore, if the pressure is increased, the equilibrium will move to the right, to the formation of NH3. If the pressure is reduced, the equilibrium shifts toward the original products.

We conclude that the chemical equilibrium can be disturbed if it is increased or decreased:

1. Temperature;

2. pressure;

3. Concentration of substances.

When the catalyst is introduced into any reaction, the balance does not change, i.e. The chemical equilibrium is not disturbed.