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Le Chatelier's Principle - Concept

Teacher/Instructor Jacqueline Spivey
Jacqueline Spivey

Ph.D.,U.C.Santa Cruz
Teaching at a top-ranked high school in SF

She teaches general and chemistry at a top-ranked high school in San Francisco. Prior to that, she lead and published a number of research studies and lectured at SF State University.

Le Chatelier's principle states that when a change in concentration, pressure, or temperature is applied to a system at equilibrium, the position of the equilibrium shifts in direction that tends to reduce the effect of that change. For instance if an amount of reactant of the product is added, the system shifts towards the removed component.

So this segment let's go ahead and talk about a principle known as Le Chatelier's Principle which is very much intertwined in the concept of chemical equilibrium. So let's go ahead and define it first, so basically when you have a change in your system, be it in concentration, pressure or temperature at, whey your system is in equilibrium and you impose these changes then the position of the equilibrium is going to shift in a direction that tend to reduce the effect of that change. It's kind of like a push, pull kind of a thing. Okay so I said concentration, pressure and temperature are the main factors that influence the equilibrium position. Pressure is related to volume as well and so I'll discuss quickly that the end how those 2 are related in terms of Le Chatelier's Principle. So another way to kind of like state this, is that if you think of a reaction you got reactants and products, when the reactant or the product or a product is added to the system that's already at equilibrium then the system shifts away from that added component. Right because the system, the tendency is to want to remaining equilibrium so it will do whatever it has to do in order to maintain that state. So similar to what I just said, if a reactant or a products is removed then the system shifts towards the removed component again to try to reestablish the equilibrium position. So I said that the changes that are associated with the system that can invoke the Le Chatelier's Principle are temperature, pressure and concentration and how are pressure and volume then related? Is that if you think about it something is getting bigger right so the volume is increasing that means that, there's a decrease in pressure.

Right there's a lot more space in the system versus if the volume is decreasing, then the pressure is going to increase. Less space, more pressure, so these guys are inversely related. So when you're thinking about Le Chatelier's Principle and applying it, if it asks you something about volume remember that volume or pressure, remember how they're related so that you can solve the problems. And that's basically the definition of Le Chatelier's Principle.