Le Chatelier's principle, temperature and industrial conditions

Le Chatelier's principle, temperature and industrial conditions

Le Chatelier's principle is a prediction tool, not a reason to ignore kinetics or economics. When concentration changes, the system shifts to consume some added substance or replace some removed substance. Increasing pressure favours the side with fewer gas moles, but only for equilibria involving gases. Temperature shifts equilibrium by favouring the endothermic direction: treating heat as a reactant or product helps. A catalyst reaches equilibrium faster but leaves Kc and equilibrium composition unchanged at fixed temperature. Industry selects compromise conditions that balance equilibrium yield, rate, energy cost, equipment limits and safety.

Work it through

For the exothermic Haber equilibrium N₂ + 3H₂ ⇌ 2NH₃ + heat, lower temperature favours ammonia at equilibrium but may make the reaction too slow. Higher pressure favours ammonia because four gas moles become two, but very high pressure is costly. A catalyst speeds reaching the chosen compromise equilibrium but does not make the equilibrium contain more ammonia at the same temperature and pressure.

Mastery target

Predict equilibrium shifts from concentration, pressure and temperature; distinguish thermodynamic yield from rate and justify industrial compromise conditions.