Le Chatelier's principle

High School

Definition

The principle that when a system at equilibrium is disturbed by a change in concentration, temperature, or pressure, it shifts to partly counteract the change and restore equilibrium. It allows chemists to predict how conditions affect a reaction's yield.

Worked examples

\(\)N\(_2\)O\(_4(g) \rightleftharpoons 2\)NO\(_2(g)\) — increase pressure → equilibrium shifts left (toward fewer gas molecules)

The system counteracts added pressure by favoring the side with fewer moles of gas.

\(\)N\(_2(g) + 3\)H\(_2(g) \rightleftharpoons 2\)NH\(_3(g) + \)heat\(\) — add heat → shifts left (endothermic direction)

Adding heat shifts the equilibrium toward the endothermic side to absorb the extra energy.

Remove product \(\)NH\(_3\) from the Haber process → equilibrium shifts right to produce more ammonia

The system responds to the drop in product concentration by making more product.

Common mistakes

The system completely reverses the stress and returns to the original position → The system shifts to *partly* counteract the change, reaching a new equilibrium Le Chatelier's principle minimizes the disturbance but does not eliminate it.
Adding a catalyst shifts the equilibrium position → A catalyst speeds up both forward and reverse reactions equally, so equilibrium position is unchanged Catalysts only change how fast equilibrium is reached, not where it lies.
Increasing volume of a gas reaction always shifts equilibrium right → Increasing volume (lowering pressure) shifts toward the side with more moles of gas The direction depends on which side has more gas particles, not left vs. right.

Where you'll use it next

You'll apply Le Chatelier's principle when optimizing industrial processes like the Haber and contact processes, predicting solubility changes, understanding buffer systems in acid-base chemistry, and analyzing physiological equilibria such as oxygen transport in blood.

Found in 1 StudyPug lesson

Understanding Le Chatelier's Principle in Chemistry

Chemistry 12

Dive into Le Chatelier's Principle and master the art of predicting chemical equilibrium shifts. Learn how temperature, pressure, and concentration changes affect exothermic and endothermic reactions in real-world applications.

12th Grade12th