Question

What is Le Chatelier's principle for systems in equilibrium?

Answer 1

Le Chatelier's principle states that when a system at equilibrium is subjected to an external perturbation, the equilibrium will move so as to offset the external perturbation.

Explanation:

To put this another way if an equilibrium is stressed, the equilibrium will move so as to offset the stress. Note that `"offset"` does not mean `"counteract"`.

For a fuller treatment, consult a text.

Typically, we would use `"Le Chatelier's Principle"` to manipulate an equilibrium, e.g.:

`N_2(g) + 3H_2(g) rightleftharpoons 2NH_3(g)`

And this is probably the most important reaction on the planet. If we reduce the concentration of ammonia (by condensation for instance) we may drive the equilibrium to the right.