Le Chatelier's PrincipleFirst, a simple reminder of Le Chatelier's principle.
When any of the conditions affecting the position of a dynamic equilibrium are changed, then the position of that equilibirum will shift to minimise that change.
As such, we know that the equilibirum position is affected by factors such as tempereature, pressure and concentration. We also know that the presence of catalysts does not affect the equilibrium position of the reaction, it merely establishes the equilbrium more rapidly.
Let us examine the effect of each of the above factors upon the famous Haber process.
N2 (g) + 3H2 (g) 2NH3 (g)
As we know, this reaction is exothermic in the forward direction, as such if the temperature were to be increased (as one might do in industry to increase the rate of reaction) the equilbirium position would shift to minimse this increase in temperature. As a reult, the reverse, endothermic reaction would increase, and the yield of ammonia would decrease.
From the reaction, we can see that there are a greater number of molecules on the left hand-side of the equation. As all of the reactants and products are gaseous, we can ignore concentration of reactants and products, and instead focus on pressure. Therefore increasing the prssure under which the reaction takes place, we can cause the equilbrium position to the right, encouraging the forward reaction. This is useful, as we know that a higher pressure can also increase the rate of reaction - and in this case also increases yield.
The iron catalyst used for the Haber process will also increase the rate of reaction, but catalyses both the forward and reverse reaction, and thus the overall equilibrium position is unaffected. |
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