Le Chatelier's Principle Calculator

Le Chatelier’s Principle states that when a system at equilibrium is disturbed, it shifts to partially counteract that disturbance. The word “partially” matters — the equilibrium does not fully undo the change, it just moves in the direction that reduces the stress.

Concentration changes are the most intuitive. Add more reactant and the system consumes some of it by shifting toward products. Remove product and the system makes more of it, also shifting forward. The equilibrium constant K does not change when you adjust concentrations — only the position of equilibrium shifts.

Temperature is different: it actually changes K. For an endothermic reaction (heat is a reactant), raising temperature favors the forward reaction, increasing K. For an exothermic reaction, raising temperature shifts the equilibrium backward, decreasing K.

Pressure changes only affect equilibria that involve gases with unequal total moles on each side. Increasing pressure favors the side with fewer gas molecules. If both sides have the same number of gas moles, pressure has no effect on the equilibrium position.

A catalyst speeds up both the forward and reverse reactions equally. It lowers the activation energy but does not change the equilibrium constant or the equilibrium position. The system reaches equilibrium faster, but arrives at the same concentrations.

Adding an inert gas at constant volume does not affect partial pressures of the reacting gases, so equilibrium does not shift. This trips students up because adding any gas at constant pressure does change partial pressures — but constant volume is the key qualifier here.

The principle applies to all reversible equilibria: acid-base, solubility, redox, and biochemical reactions like hemoglobin-oxygen binding.