Pressure and chemical equilibrium transfer
According to Le Châtelier, if the pressure is increased, the position of equilibrium will move so that the pressure is reduced again. The system can reduce the pressure by reacting in such a way as to produce fewer molecules.
If the pressure is decreased, the equilibrium will move in such a way that the pressure increases again. It can do that by producing more gaseous molecules. In this case, the position of equilibrium will move towards the left-hand side of the reaction.
Le Châtelier’s principle is used to predict what reactions will occur when the external conditions change.