Understanding equilibrium – the advanced stuff!

Last month’s blog post focused on introducing you to the basics of equilibrium. This month it is my intention to introduce you to the more advanced stuff.

It is possible for chemists to manipulate a reaction at equilibrium in order to increase (or decrease) the amount of products. In order to do this, chemists will change the concentration of products or reactants, change the temperature of the reaction, change the pressure of the reaction or use a catalyst.

The chemist will also apply Le Chatelier’s principle. Le Chatelier’s principle Is a law of opposites. Whatever change you impose on a reaction it will try to do the opposite. So if you change the concentration of the products the equilibrium will do the opposite and decrease the concentration of products. Let us now consider the effect of changing concentration, pressure, temperature of a reaction.

Concentration: As already mentioned if you increase the concentration of products, the reaction will try to decrease the concentration of products. The only way it can do this is to turn the products back into reactants, so increasing the concentration of products decreases the amount of product. So, what do you do if you wish to obtain more products? The answer is to either increase the concentration of reactants as the reaction would decrease the concentration of the reactants by making more products or by decreasing the concentration of products. In this situation, the reaction will try to increase the concentration of products and the only way it can do this is to turn more reactants into products.

Fritz Haber – By The Nobel Foundation

The Haber process, which is used to manufacture ammonia, takes advantage of this factor. Any ammonia that is produced is liquefied and removed from the reaction. This has the effect of reducing the concentration of the product so more is produced. Ammonia is made from nitrogen and hydrogen and any unreacted nitrogen and hydrogen is also recycled which has the effect of increasing the concentration of reactants. These reactants well then react to make more ammonia.

In my next blog post I will look at how changing pressure and temperature affects a reaction at equilibrium.