The ultimate molar solubility of a sparingly soluble salt is strictly governed by its defined solubi — Ionic Equilibrium Chemistry Question
Question
The ultimate molar solubility of a sparingly soluble salt $MX$ is strictly governed by its defined solubility product $K_{sp}$. Which of the following specific conditions or physical interventions will definitively alter the absolute amount of solid $MX$ that can dissolve in a given volume of solvent?
💡 Solution & Explanation
The classic common ion effect (Option A) drastically suppresses solubility by shifting the dissolution equilibrium backward. Changing the system temperature (Option B) alters the actual thermodynamic equilibrium constant $K_{sp}$, directly changing solubility. Introducing a strong complexing agent (Option C) removes free $M^+$ ions from the solution, heavily shifting the dissolution equilibrium forward and increasing solubility. Adding more solid salt (Option D) to an already saturated solution does not shift the equilibrium or change the molar solubility, as the activity of a pure solid is rigidly defined as constant (unity).