HSC Chemistry — Module 5
Le Chatelier’s Principle — Flashcards & Quiz
Le Chatelier’s principle states that a system at equilibrium will shift to partially counteract any change imposed on it. In HSC Chemistry Module 5, you must predict how changes in concentration, temperature, pressure, and volume affect equilibrium position. Understanding that catalysts do not shift equilibrium (they only speed up attainment) is a common exam trap. Questions frequently present industrial scenarios like the Haber process and ask you to explain optimal conditions using Le Chatelier’s principle.
Sample Flashcards
Q1: State Le Chatelier's principle.
If a system at equilibrium is subjected to a change in concentration, temperature or pressure, the system will shift to partially counteract the change and establish a new equilibrium position.
Q2: How does changing concentration affect equilibrium?
Increasing the concentration of a reactant shifts equilibrium toward the products (right). Increasing the concentration of a product shifts equilibrium toward the reactants (left). The system consumes the added substance to partially restore the original ratio.
Q3: How does changing temperature affect equilibrium?
Increasing temperature favours the endothermic direction. Decreasing temperature favours the exothermic direction. Temperature is the ONLY factor that changes the value of Kc.
Q4: How does changing pressure affect equilibrium in gaseous systems?
Increasing pressure shifts equilibrium toward the side with FEWER moles of gas (to reduce pressure). Decreasing pressure shifts toward the side with MORE moles of gas. Pressure changes only affect equilibria involving different moles of gas on each side.
Q5: What happens to equilibrium when an inert gas is added at constant volume?
Adding an inert gas at constant volume does NOT affect equilibrium. The concentrations of reactants and products remain unchanged because the volume hasn't changed, so partial pressures of the reacting gases are unaffected. No shift occurs.
Sample Quiz Questions
Q1: Adding more reactant to a system at equilibrium shifts the equilibrium to the right.
Answer: TRUE
Increasing reactant concentration shifts equilibrium toward the products (right) to partially counteract the increase.
Q2: Increasing temperature always shifts equilibrium to the right.
Answer: FALSE
Increasing temperature shifts equilibrium toward the ENDOTHERMIC direction — this could be right (if forward is endothermic) or left (if forward is exothermic).
Q3: Increasing pressure shifts equilibrium toward the side with more moles of gas.
Answer: FALSE
Increasing pressure shifts equilibrium toward the side with FEWER moles of gas, to reduce the total pressure.
Last updated: March 2026 · 7 flashcards · 6 quiz questions