Effect of Pressure Change
The shift in a gaseous equilibrium caused by changing the total pressure through a volume change.
Formula / equation
shift towards fewer gas moles when p rises
Unit
Pa
In depth
Compressing the system favours the side with fewer gas molecules, since that reduces the pressure. If both sides have equal numbers of gas molecules, pressure has no effect on the position. Pressure changes do not alter the value of K itself.
Examples in the real world
High pressure improves ammonia yield because four moles of gas become two.