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Common Ion Effect
AP Chemistry · Unit 7 Equilibrium
Learning Objectives
Explain how common ions shift solubility equilibrium
Calculate new solubility with added common ion
Apply Le Chatelier's principle to Ksp
Compare Q vs Ksp for precipitation prediction
Key Concept
Adding a common ion
decreases
solubility.
Le Chatelier: adding product ion → equilibrium shifts LEFT → less dissolves.
Ksp remains constant (only changes with T).
Tags
common ion
Ksp
solubility
Le Chatelier
SELECT SALT
AgCl (Ksp = 1.77×10⁻¹⁰)
PbCl₂ (Ksp = 1.17×10⁻⁵)
BaSO₄ (Ksp = 1.08×10⁻¹⁰)
CaF₂ (Ksp = 3.45×10⁻¹¹)
[Common Ion] (M)
0.00
Pure Solubility
—
With Common Ion
—
Reduction
—
Ksp
—