Chemical equilibrium — Grade 12 Past Paper Questions

Iodine and chlorine gas equilibrium forming iodine trichloride. State Le Chatelier's principle, explain why masses plateau at equilibrium, determine volume direction from pressure adjustment, identify alternative changes producing equivalent effects, and calculate moles of iodine added using Kc.

Use forward and reverse reaction rate graphs to analyse an equilibrium system disturbed by concentration and temperature changes. Determine direction of concentration shift, apply Le Chatelier's principle to identify temperature change direction, and locate when the system re-establishes equilibrium.

Carbon disulfide and chlorine gas reach equilibrium forming carbon tetrachloride and sulphur dichloride. State Le Chatelier's principle, calculate initial moles of carbon disulfide using equilibrium concentrations and Kc, and predict yield changes when volume is increased or products are removed.

Multiple-choice questions on identifying which system change—catalyst addition, pressure adjustment, temperature shift, or concentration change—caused observed rate changes in the ammonia synthesis equilibrium, and matching an equilibrium constant expression to its corresponding reaction equation.

Multiple-choice questions on writing the reaction equation from an equilibrium constant expression, and distinguishing the endpoint from the equivalence point in a titration.

Multiple-choice covering energy profile analysis for reversible reactions, identifying activation energy components, effect of catalysts, and acid-base indicator equilibrium shifts using Le Chatelier's principle.