AP Chemistry Questions: Solubility and Ksp

🧪 Quick Study Guide

• ⚖️ Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature, usually expressed in grams per liter (g/L) or moles per liter (mol/L).
• ⚗️ Saturated solutions are solutions where the maximum amount of solute is dissolved; any additional solute will not dissolve and will instead precipitate out.
• 🔢 The solubility product constant, $K_{sp}$, is the equilibrium constant for the dissolution of a sparingly soluble ionic compound. For example, for $AgCl(s) \rightleftharpoons Ag^+(aq) + Cl^-(aq)$, $K_{sp} = [Ag^+][Cl^-]$.
• 📈 A higher $K_{sp}$ value indicates higher solubility of the compound.
• 🌡️ Solubility is affected by temperature. For most ionic compounds, solubility increases with increasing temperature.
• Common Ion Effect: The solubility of a sparingly soluble salt is reduced when a common ion is added to the solution.
• pH Effects: The solubility of some salts is affected by pH, particularly those containing basic anions like $OH^-$, $CO_3^{2-}$, and $S^{2-}$.

Practice Quiz

1. Which of the following salts is the *least* soluble, given their respective $K_{sp}$ values?
   1. $AgCl$, $K_{sp} = 1.8 \times 10^{-10}$
   2. $PbCl_2$, $K_{sp} = 1.6 \times 10^{-5}$
   3. $AgBr$, $K_{sp} = 5.0 \times 10^{-13}$
   4. $CaF_2$, $K_{sp} = 3.9 \times 10^{-11}$
2. The solubility of $PbCl_2$ in water is $1.6 \times 10^{-2}$ M. What is the $K_{sp}$ for $PbCl_2$?
   1. $1.6 \times 10^{-5}$
   2. $3.2 \times 10^{-4}$
   3. $1.6 \times 10^{-4}$
   4. $2.1 \times 10^{-5}$
3. What is the effect of adding $HCl$ to a saturated solution of $AgCl$?
   1. The solubility of $AgCl$ increases.
   2. The solubility of $AgCl$ decreases.
   3. The solubility of $AgCl$ remains unchanged.
   4. $AgCl$ will precipitate out of the solution.
4. The $K_{sp}$ of $Mg(OH)_2$ is $5.6 \times 10^{-12}$. Calculate the solubility of $Mg(OH)_2$ in mol/L.
   1. $1.1 \times 10^{-6}$
   2. $8.4 \times 10^{-7}$
   3. $1.1 \times 10^{-4}$
   4. $2.2 \times 10^{-4}$
5. Which of the following will *not* affect the solubility of $BaSO_4$?
   1. Temperature
   2. Addition of $BaCl_2$
   3. Addition of $Na_2SO_4$
   4. Addition of $NaCl$
6. The solubility of $Ag_2CrO_4$ is $6.7 \times 10^{-5}$ M. Calculate the $K_{sp}$.
   1. $3.0 \times 10^{-12}$
   2. $1.2 \times 10^{-12}$
   3. $4.0 \times 10^{-13}$
   4. $3.0 \times 10^{-13}$
7. Will a precipitate of $CaF_2$ form if $[Ca^{2+}] = 1.0 \times 10^{-4}$ M and $[F^-] = 2.0 \times 10^{-4}$ M? ($K_{sp}$ for $CaF_2 = 3.9 \times 10^{-11}$)
   1. Yes
   2. No
   3. Maybe
   4. Cannot be determined