According to one of the classifications used to describe the chemical processes, there are two types of opposite reactions - reversible and irreversible.The reversible reaction does not go to completion, i.e.none of the substances which have entered into it, is not consumed completely and does not change the concentration.This process ends with the establishment of chemical equilibrium or balance, which represent ⇌.However, the forward and reverse reactions proceed further without stopping, so the balance is called dynamic or moving.Treading chemical equilibrium indicates that the direct reaction occurs at the same speed (V1), and that the inverse (V2), V1 = V2.If the pressure and temperature are constant, the equilibrium in the system can last indefinitely.
quantitative chemical equilibrium is described by the equilibrium constant that is the ratio of direct constants (K1) and reverse (K2) reactions.Calculate it can be defined as: K = K1 / K2.Performance of the equilibrium constant will depend on the composition of the reactants and temperature.
Displacement of chemical equilibrium occurs on the principle of Le Chatelier, which reads: "If a system that is in equilibrium, influence by external factors, the equilibrium is disturbed and displaced in the direction opposite to this change."
Consider chemical equilibrium and conditions of its displacement by the example of the formation of ammonia molecules: N2 + 3H2 ↔ 2NH3 + Q.
Considering the equation of the reaction set:
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direct reaction - a reaction compound, because.2 simple substances formed by complex 1 (ammonia), and the reverse - decomposition;
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direct reaction is the formation of heat, so it is - an exothermic, therefore, reverse - and comes with an endothermic absorption of heat.
Now consider this equation subject to modification of certain parameters:
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change in concentration.If you increase the concentration of initial substances - nitrogen and hydrogen - and reduce the amount of ammonia, the equilibrium is shifted to the right to the formation of NH3.If you want to move it to the left, increase the concentration of ammonia.
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Rising temperatures will move the balance to the side reaction in which heat is absorbed, and with decreasing - is released.Therefore, if the temperature increase in the synthesis of ammonia, the equilibrium is shifted toward the starting materials, i.e.the left, and when the temperature - to the right, to the reaction product side.
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If you increase the pressure, the balance moves to the side, where the amount of gaseous substances less, and when the pressure decreases - in the direction where the amount of gas increases.In the synthesis of NH3 from 4 mol of N2 and 3H2 turns 2 NH3.Therefore, if we increase the pressure, the balance moves to the right, to the formation of NH3.If the pressure is reduced, the equilibrium is shifted toward the starting materials.
We conclude that the chemical equilibrium can be disturbed if the increase or decrease:
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temperature;
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pressure;
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concentration of substances.
The introduction of a catalyst in any reaction balance does not change, ie,chemical equilibrium is not disturbed.
