45. SHIFT OF THE CHEMICAL EQUILIBRIUM.

 

The provision of chemical equilibrium depends on the following paramktr of reaction: temperatures, pressure and concentration. Impact which is exerted by these factors on chemical reaction submit to pattern which has been stated in general view in 1884 by the French scientist Le-Chatelie. Modern formulation of the principle of Le-Chatelie is as follows:

If on the system which is in balanced state to make external impact, then the system will pass into other state so that to reduce effect of external influence.

1. Temperature effect. In each reversible reaction one of the directions answers exothermic process, and another - endothermic.

N2 + 3H2 2NH3 + Q

Direct reaction - exothermic, and reverse reaction - endothermic. Influence of change of temperature on the provision of chemical equilibrium submits to the following rules:

At temperature increase the chemical equilibrium is displaced in the direction of endothermic reaction, at fall of temperature - in the direction of exothermic reaction.

2. Influence of pressure. In all reactions with participation of the gases which are followed by change of volume due to change of amount of substance at pereokhoda from mother substances to products position of balance is influenced by pressure in system.
Influence of pressure upon position of balance submits to the following rules:

At build-up of pressure balance moves in the direction of formation of substances (initial or products) with smaller volume; at pressure decline balance moves in the direction of formation of substances with large volume

Thus, upon transition from mother substances to products the volume of gases has decreased twice. Means, at build-up of pressure balance is displaced towards formation of NH3 what the following data for fusion reaction of ammonia at 400 0C confirm:

pressure, MPa	0,1	10	20	30	60	100
volume ratio of NH3, %	0,4	26	36	46	66	80

3. Concentration influence. Influence of concentration on balanced state submits to the following rules:

When strengthening one of mother substances balance moves in the direction of formation of reaction products; when strengthening one of reaction products balance moves in the direction of formation of mother substances.

 

   

 

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