Le Chatelier’s Principle: Getting More (or Less) Product

If you’re, say, an industrial chemist, you want as much of the reactants as possible to be converted to product. You’d like the reaction to go to completion (meaning you’d like the reactants to keep creating the product until they’re all used up), but that doesn’t happen for an equilibrium reaction. But it would be nice if you could, in some way, manipulate the system to get a little bit more product formed. There is such a way — through Le Chatelier’s Principle.

A French chemist, Henri Le Chatelier, discovered that if you apply a change of condition (called stress) to a chemical system that’s at equilibrium, the reaction will return to equilibrium by shifting in such a way as to counteract the change (the stress). This is called Le Chatelier’s Principle. You can stress an equilibrium system in three ways:

✓ Change the concentration of a reactant or product.

✓ Change the temperature.

✓ Change the pressure on a system that contains gases.

In this section, you see how this applies to the Haber process:

N_2(g) + 3H_2(g) ↔ 2NH_3(g) + heat