Nimo

Study smarter with Nimo

Personalised revision that adapts to you. Ace your revision with unlimited practice questions that are designed to help you learn faster. We're slowly rolling out to more and more students.

Try Nimo

Qualitative predictions for chemical equilibrium shifts

The rate and extent of chemical change • Reversible reactions and equilibrium

Key concepts

What you'll likely be quizzed about

  • Le Chatelier’s principle states that a system at equilibrium responds to an external change by shifting in the direction that reduces the effect of that change.
  • This principle applies to alterations in concentration, pressure, temperature, and catalyst presence-ensuring the system is closed and reversible.
  • Use the balanced equation to identify whether the shift favors the reactants or products.

Flashcards

Test your knowledge with interactive flashcards

Effect of adding a reactant

Click to reveal answer

Adding a reactant causes the equilibrium to shift toward products to consume the extra reactant.

Key notes

Important points to keep in mind

State the cause, then the direction of shift, then any change to K if temperature is involved.

Le Chatelier’s principle gives direction only; it does not provide magnitudes.

Only temperature changes alter the equilibrium constant K.

Count only gaseous moles when predicting pressure effects.

Pure solids and pure liquids are excluded from K expressions.

Adding an inert gas at constant volume does not affect the equilibrium position.

Catalysts speed up attainment of equilibrium but do not change K or the final position.

If reaction enthalpy is unknown, temperature effects cannot be predicted qualitatively.

Use Q versus K to predict spontaneous direction after any disturbance.

Assume a closed system unless otherwise stated.

Built with v0