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Equilibrium and Le Chatelier's Principle lab

Although we have considered reactions up to this point to go completely to products, most reactions are actually at equilibrium.  This means that when you have done a reaction, and it is sitting there on the counter - you will have products in there, and also some reactants!  What is a product or a reactant?

A reactant is listed first in a equation, and a product is listed after the arrow in a equation.

When you are at equilibrium, the rates of transformation of reactant into product, and product into reactant are equal.  Therefore the concentrations of all chemicals in the reaction remain constant.  Does this mean the concentrations equal eachother?  NO, IT DOES NOT!

Le Chatelier's principle is the way to describe what happens when an outside stress is imposed on the system.  What is an outside stress?  Well you could add some more reactant or product, or you could take them away, you could increase or decrease temperature, or pressure, or volume.  The principle says - if you add stress to a system that is at equilbrium, the equilibrium of that system will respond so as to UNDO the stress.  It is kind of like the physics principle - "For every action, there is an opposite and equal reaction".

Here is a really cool website that has an animation where you can see what happens on the microscopic level when you add a stress to a system.  It also has a guy talking to you about it, so you can hear what is happening also.

If you need more practice in setting up these type of problems - here is a website that will test you on your skills.  Just hit "New Question", and one will pop up, and it will even grade which ones you have done correct!

Posted at 09:15AM Jul 31, 2006 by CHRISTIAN, CAROLINE in General  |  Comments[2]