Le Chatelier's principle

This was all summarized nicely by a French chemist named Henri-Louis Le Chatelier, who was born in Paris in 1850.

Today, we call his summary Le Chatelier's Principle, and it says that if stress is placed on a system that is at equilibrium, the system will proceed in a direction that minimizes the stress.

That can happen in several ways.

For starters, changing the concentration of any substance in a reaction causes it to proceed in whatever direction restores the former balance.