# Explain raising and decreasing the volume of a system in equilibrium equations?

Okay, so i'm taking chemistry and we're in the equilibrium unit and we're supposed to be using Le Chatelier's law to determine what will happen to an equation if we add any particular element to it. I understand most of it, but I get confused when it comes to increasing or decreasing volume.

If we had an equation like:

2SO2(g) + O2(g) <=> 2SO3(g) + heat

and our goal is to manipulate the reaction so that we gain more SO3 would we raise or lower the volume?

How do you tell is what I'm really trying to ask?

If you increase volume, that means you're decreasing the concentration, right? So if you do that, does the reaction go to the side with more or less gas?

And vice versa?

Any help would be appreciated .

Relevance

In the state of equilibrium, any changes occurs, the system will counter balance by opposing the changes.

moles on the LHS = 3

moles on the RHS = 2

If we increase the volume of the it changes the partial pressure, therefore the equilibrium counter balance will would increase the RHS (SO3) that it has fewer mole.

If you increase volume, that means you're decreasing the concentration, right? Wrong, it stated that the volume is changed by 'add any particular element to it' (example: we pump in He to change the volume, therefore there is no change in concentration)

Source(s): 'Effect of change in pressure' http://en.wikipedia.org/wiki/Le_Chatelier's_princi...
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