Changes in pressure ordinarily do not affect the concentration of reacting species in condensed phases (say, in an aqueous solution) because liquids & solids are virtually incompressible. On the other hand, concentration of gases are greatly affected by changes in pressure.
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PV=nRT |
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P=(n/V)RT |
Note that P & V are related to each other inversely: The greater the pressure, the smaller the volume, and vice versa. Note, too, that the term (n/V) is the concentration of the gas in mol/dm3, and it varies directly with pressure.
Le Chatelier / Le Chatelier's Principle
Changes in concentration / Changes in temperature / Summary