Effect of Concentration Change

Let us use the Haber process for the manufacture of ammonia as an example. This reaction is shown again here. 

Let us open the reaction chamber and pump in some nitrogen. This act places a concentration stress on the system consisting of an increase in the concentration of the Nj. According to Le Chatelier s principle, the equilibrium must shift to relieve this stress. This would mean consuming some of the Nj in order to return to equilibrium. Thus the equilibrium shifts to the right, as indicated here 

Similarly, if we were able to somehow open the container and selectively pump out some of the hydrogen, this would also be a concentration stress. In this case, however, the equilibrium would shift to replace the hydrogen that was removed. This would mean a shift to the left, or toward the hydrogen in the equation so that more would be produced. 

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Neglecting the effects of concentration changes on solvent density, the phase... 

The effect of concentration changes were observable in the two systems described above. For the system A + B c C + D, an increase in the concentration of A and/or B will shift the position of equilibrium to the right-hand side. For example, on increasing the concentration of A, some of the added A reacts with substance B to produce more C and D until equilibrium is re-established. Similarly, if the concentration of C and/or D is increased, the position of equilibrium is shifted to the left-hand side. Removal of a component, e.g. substance A, will cause the system to respond in such a way as to oppose the change, i.e. the decrease in the concentration of A. Therefore, the equilibrium position shifts to the left-hand side. 

Neglecting the effects of concentration changes on solvent density, the phase volumes will remain constant. Thus for the liquid phase with volume VL... 

Because of variations in both radiation conditions and absorber concentrations, the actual absorption rates in an urban atmosphere will be highly variable. For example, Figure 26 shows the effect of concentration changes on the absorption rate... 

FIGURE 14.5 Effect of concentration change on the position of equilibrium, fa) An aqueous Fe(SCN)s solution. The color of the solution is due to both the red FeSCN and the yellow Fe species, (bj After the addition of some NaSCN to the solution in (a), the equilibrium shifts to the left, (c) After the addition of some FefNO j to the solution in (a), the equilibrium shifts to the left, (d) After the addition of some H2C2O4 to the solution in (a), the equilibrium shifts to the right. The yellow color is due to the Fe(C204) ions. 

The effects of concentration changes on equilibrium can be rationalized by considering the reaction quotient, Q, and comparing it to the equilibrium constant, K. 

The effect of concentration changes can be illustrated by the reaction of H2 with... 

Le ChStelier s principle can be used to predict the effect of changes in concentration (or pressure for gas phase reactions) and temperature on the position of an equilibrium in terms of the proportions of reactants and products in the equilibrium mixture. The equilibrium law can be used to explain and quantify the effect of concentration changes at a given temperature. Such explanations are based on the fact that the value of the equilibrium constant, K,., is itself not affected by a change in concentration. 

A new Figure 13.11 has been added, illustrating the effect of concentration changes on equilibrium. 

OH and NH bands in the near infrared exhibit temperature effects resembling the effect of concentration changes... 

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