AP Chemistry Questions on Solubility Equilibrium (Ksp)

📚 Quick Study Guide

• ⚖️ Solubility equilibrium is a state where the rate of dissolution of a solid equals the rate of precipitation of its ions in a solution.
• 🧪 The solubility product constant, $K_{sp}$, represents the equilibrium constant for the dissolution of a sparingly soluble salt.
• 📝 For a salt $A_xB_y$ dissolving according to the equation $A_xB_y(s) \rightleftharpoons xA^{y+}(aq) + yB^{x-}(aq)$, the $K_{sp}$ expression is $K_{sp} = [A^{y+}]^x[B^{x-}]^y$.
• 🔢 Molar solubility (s) is the number of moles of the salt that dissolve per liter of solution.
• 🌡️ The solubility of a salt is affected by temperature, common ion effect, and pH.
• 💡 A smaller $K_{sp}$ value indicates lower solubility.
• ➕ The common ion effect decreases the solubility of a sparingly soluble salt when a soluble salt containing a common ion is added to the solution.

🧪 Practice Quiz

1. Which of the following expressions represents the solubility product constant, $K_{sp}$, for $AgCl(s)$?
   1. $K_{sp} = [Ag^+][Cl^-]$
   2. $K_{sp} = \frac{1}{[Ag^+][Cl^-]}$
   3. $K_{sp} = \frac{[AgCl]}{[Ag^+][Cl^-]}$
   4. $K_{sp} = [AgCl]$
2. The $K_{sp}$ of $CaF_2$ is $3.9 \times 10^{-11}$. What is the molar solubility of $CaF_2$ in water?
   1. $2.0 \times 10^{-4} M$
   2. $3.4 \times 10^{-6} M$
   3. $2.1 \times 10^{-4} M$
   4. $1.6 \times 10^{-4} M$
3. What is the effect of adding $AgNO_3$ to a saturated solution of $AgCl$?
   1. The solubility of $AgCl$ increases.
   2. The solubility of $AgCl$ decreases.
   3. The solubility of $AgCl$ remains the same.
   4. $AgNO_3$ precipitates out of the solution.
4. The $K_{sp}$ for $PbCl_2$ is $1.6 \times 10^{-5}$. What is the $[Pb^{2+}]$ in a solution prepared by mixing $100 mL$ of $0.02 M$ $Pb(NO_3)_2$ with $100 mL$ of $0.2 M$ $NaCl$?
   1. $1.6 \times 10^{-5} M$
   2. $4.0 \times 10^{-4} M$
   3. $8.0 \times 10^{-4} M$
   4. $2.0 \times 10^{-4} M$
5. For the reaction $Mg(OH)_2(s) \rightleftharpoons Mg^{2+}(aq) + 2OH^-(aq)$, the $K_{sp} = 5.6 \times 10^{-12}$. At what pH will a $Mg(OH)_2$ solution be at equilibrium when $[Mg^{2+}] = 1.0 \times 10^{-3} M$?
   1. $pH = 8.23$
   2. $pH = 10.77$
   3. $pH = 5.23$
   4. $pH = 3.23$
6. Which of the following salts will have the highest molar solubility, given their respective $K_{sp}$ values?
   1. $AgI$, $K_{sp} = 8.5 \times 10^{-17}$
   2. $CuI$, $K_{sp} = 5.0 \times 10^{-12}$
   3. $PbI_2$, $K_{sp} = 9.8 \times 10^{-9}$
   4. $BiI_3$, $K_{sp} = 8.1 \times 10^{-19}$
7. Will a precipitate of $PbCl_2$ form when $10.0 mL$ of $0.010 M$ $Pb(NO_3)_2$ is mixed with $10.0 mL$ of $0.020 M$ $NaCl$? ($K_{sp}$ of $PbCl_2 = 1.6 \times 10^{-5}$)
   1. Yes, because $Q > K_{sp}$
   2. No, because $Q < K_{sp}$
   3. Yes, because $Q < K_{sp}$
   4. No, because $Q > K_{sp}$