Le Chatelier's Principle

principle LE CHATELIER'S PRINCIPLE This page looks at Le Chatelier's Principle and explains how to apply it to reactions in a state of dynamic equilibrium. It covers changes to the position of equilibrium if you change concentration, pressure or temperature. It also explains very briefly why catalysts have no effect on the position of equilibrium. |

| Important:  If you aren't sure about the words dynamic equilibrium or position of equilibrium you should read the introductory page before you go on |

It is important in understanding everything on this page to realise that Le Chatelier's Principle is no more than a useful guide to help you work out what happens when you change the conditions in a reaction in dynamic equilibrium. It doesn't explain anything. I'll keep coming back to that point! Using Le Chatelier's PrincipleA statement of Le Chatelier's Principle * If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change. Using Le Chatelier's Principle with a change of concentrationSuppose you have an equilibrium established between four substances A, B, C and D. |

| Note:  In case you wonder, the reason for choosing this equation rather than having just A + B on the left-hand side is because further down this page I need an equation which has different numbers of molecules on each side. I am going to use that same equation throughout this page. |

What would happen if you changed the conditions by increasing the concentration of A?According to Le Chatelier, the position of equilibrium will move in such a way as to counteract the change. That means that the position of equilibrium will move so that the concentration of A decreases again - by reacting it with B and turning it into C + D. The position of equilibrium moves to the right.This is a useful way of converting the maximum possible amount of B into C and D. You might use it if, for example,...