Le Chatelier's Principle states that if an external stress (changes in concentration, volume, pressure or temperature) is applied to a system at equilibrium, the system will adjust itself, trying to offset the applied stress in order to reach a new equilibrium position.

Increasing the concentration of the product shifts the equation to the left. Decreasing the concentration of the product shifts the equation to the right.

In general, an increase in pressure (decrease in volume) favours the net reaction that decrease the total number of moles of gases.

For reaction in which there is no change of the total number of moles of gases, a pressure / volume change has no effect on the position of equilibrium.

A temperature increase favours an endothermic reaction, and a temperature decrease favours an exothermic reaction.