7–9% of the AP exam. 8 key topics. 4 common errors analyzed.
Unit 7 (Equilibrium) is part of the AP Chemistry core curriculum. Work through each key topic in sequence, constructing ICE tables, net ionic equations, or energy diagrams as appropriate.
These are the most frequently penalized mistakes on AP exam FRQs and MCQs. Review each before your next practice session.
Including pure solids or pure liquids in equilibrium constant expressions (K, Ksp) — their concentrations are constant and by convention omitted, a rule students frequently overlook under exam pressure
Constructing incomplete ICE tables — omitting a species, using the wrong initial concentration, or forgetting that the change row must be proportional to stoichiometric coefficients
Comparing Q to K in the wrong direction: concluding the reaction shifts right when Q > K (it should shift left to decrease Q toward K)
Applying Le Chatelier's principle qualitatively without addressing all relevant stresses simultaneously, especially when both concentration and temperature changes are introduced in the same scenario
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