The fact of the existence of the principle of Le Chatelier many of you know from school.But few understand and can explain what exactly is the well-known principle.
French scientist told the world about the law of dynamic equilibrium in 1884.For the end of the nineteenth century discovery was very important and immediately attracted the attention of the scientific community.But due to the lack of international scientific cooperation and a half centuries ago, the scientific breakthrough of Le Chatelier only knew his countrymen.In 1887, the displacement of the chemical equilibrium in the external conditions change, said the German scientist Karl Ferdinand Braun, independently discovered the same scientific law, being-briefed about the French Open.Not by chance, this principle is often referred to the principle of Le Chatelier - Brown.
So what is the principle of Le Chatelier?
in equilibrium systems always strive to maintain its balance and resist external forces, factors and conditions.This rule applies to all systems and for all processes: chemical, electrical, mechanical, thermal.Of particular practical importance of Le Chatelier's principle is to reversible chemical reactions.
impact of temperature on the reaction rate is directly dependent on the type of reaction thermal effect.As the temperature increases, a shift of balance towards the endothermic reaction.Lowering the temperature, respectively, leads to a shift of chemical equilibrium towards exothermic reaction.The reason for this is seen in the fact that during injection system balance by external forces, it goes into a state less dependent on external factors.The dependence of endothermic and exothermic processes from equilibrium is expressed by van't Hoff:
V2 = V1 * y (T2-T1) / 10,
where V2 - is the speed of a chemical reaction with the modified temperature, V1 - the initial reaction rate,y - an indicator of the temperature difference.
Swedish scientist Arrhenius derived a formula exponential dependence of the reaction rate on temperature.
K = A • e (-E (RT)), where E - activation energy, R - the universal gas constant, T- temperature in the system.The value A is constant.
With increasing pressure, a shift of the chemical equilibrium in the direction where the substance take up less volume.If the volume of the starting materials greater than the volume of the reaction products, the equilibrium is shifted toward the starting components.Accordingly, if the amount exceeds the amount of the reaction products of reactants, the equilibrium is shifted towards the resulting chemical compounds.It is assumed that each mole of gas occupies the same volume under normal conditions.But changing the pressure in the system does not always affect the chemical equilibrium.Le Chatelier's principle indicates that the addition of inert gas into the reaction changes the pressure, but the system is in equilibrium.When this reaction is only important that the pressure which is associated with the reactants (helium has no free electrons, it does not react with the substances in the system).
Addition reaction a certain amount of a substance leads to a shift of the equilibrium to the side of the process where this substance becomes less.
Equilibrium is dynamic.It is "broken" and "aligned" naturally in the course of the reaction.To explain this situation through an example.When the hydrogenation of a solution of bromine formed hydrobromic acid.There comes a moment when the final product is formed too much, its volume exceeds the total volume monomolecule hydrogen and bromine, the reaction rate is slowed down.If added to the system is hydrogen or bromo, the reaction goes in the opposite direction.
