Introduction to Solubility Equilibria - AP Chemistry

1. Identify the $K_{sp}$ expression for $BaSO_4$.

   $K_{sp} = [Ba^{2+}][SO_4^{2-}]$. 1:1 stoichiometry gives simple product of ion concentrations.

2. Identify the $K_{sp}$ expression for $CuS$.

   $K_{sp} = [Cu^{2+}][S^{2-}]$. 1:1 stoichiometry for copper(II) sulfide dissolution.

3. Identify the $K_{sp}$ expression for $PbSO_4$.

   $K_{sp} = [Pb^{2+}][SO_4^{2-}]$. 1:1 stoichiometry for lead(II) sulfate dissolution.

4. What is the $K_{sp}$ expression for $Fe(OH)_3$?

   $K_{sp} = [Fe^{3+}][OH^-]^3$. Stoichiometry: 1 $Fe^{3+}$ and 3 $OH^-$ ions per formula unit.

5. How does $pH$ affect solubility of compounds containing basic anions?

   Increases solubility at lower $pH$. Acidic conditions protonate basic anions, reducing their concentration.

6. What is the unit of $K_{sp}$ for $CaF_2$?

   $mol^3$/$L^3$. Units from $[Ca^{2+}][F^-]^2$ concentration terms.

7. How does the presence of a common ion affect solubility?

   Decreases solubility. Le Chatelier's principle: excess ion shifts equilibrium toward solid.

8. Identify the $K_{sp}$ expression for $CdS$.

   $K_{sp} = [Cd^{2+}][S^{2-}]$. 1:1 stoichiometry for cadmium sulfide dissolution.

9. Which compound is more soluble: $CaF_2$ or $SrF_2$?

   $SrF_2$ (higher $K_{sp}$ value). Compare $K_{sp}$ values directly for same formula type.

10. Calculate $K_{sp}$ for $Ag_2S$ with $[Ag^+] = 2x$ and $[S^{2-}] = x$.

    $K_{sp} = 4x^3$. For $Ag_2S$: $K_{sp} = [Ag^+]^2[S^{2-}] = (2x)^2(x) = 4x^3$.

11. Identify the $K_{sp}$ expression for $Ca_3(PO_4)_2$.

    $K_{sp} = [Ca^{2+}]^3[PO_4^{3-}]^2$. Stoichiometry: 3 $Ca^{2+}$ and 2 $PO_4^{3-}$ per formula unit.

12. How does complex ion formation affect solubility?

    Increases solubility. Complex formation removes free metal ions from solution.

13. Which has higher solubility: $BaSO_4$ or $SrSO_4$?

    $SrSO_4$ (higher $K_{sp}$ value). Compare $K_{sp}$ values; larger value indicates higher solubility.

14. State the formula to calculate $Q_{sp}$.

    $Q_{sp} = [cation]^m[anion]^n$. Same form as $K_{sp}$ but uses current concentrations, not equilibrium.

15. Determine $K_{sp}$ for $Ag_2S$ if $[Ag^+] = 2x$ and $[S^{2-}] = x$ at equilibrium.

    $K_{sp} = 4x^3$. Substitute equilibrium concentrations: $(2x)^2(x) = 4x^3$.

16. What is the relationship between $K_{sp}$ and $Q_{sp}$?

    Precipitation occurs if $Q_{sp} > K_{sp}$. $Q_{sp}$ compares current ion concentrations to equilibrium values.

17. What is the effect of adding $NH_3$ to $AgCl$ solubility?

    Increases due to complexation. $NH_3$ forms $[Ag(NH_3)_2]^+$ complex, removing $Ag^+$ ions.

18. Explain the role of $pH$ in the solubility of $CaCO_3$.

    Solubility increases in acidic conditions. Acid protonates $CO_3^{2-}$ to form $HCO_3^-$ and $H_2CO_3$.

19. What does a large $K_{sp}$ value indicate about solubility?

    Compound is more soluble. Higher $K_{sp}$ means more ions can dissolve at equilibrium.

20. Which compound will precipitate first: $AgCl$ or $AgBr$?

    $AgBr$ (lower $K_{sp}$ value). Lower $K_{sp}$ means less soluble, so precipitates first.

21. What is the effect of $pH$ on the solubility of $Mg(OH)_2$?

    Solubility decreases at higher $pH$. Higher $pH$ increases $[OH^-]$, shifting equilibrium toward solid.

22. What is the $K_{sp}$ expression for $Al(OH)_3$?

    $K_{sp} = [Al^{3+}][OH^-]^3$. Aluminum hydroxide: 1 $Al^{3+}$ and 3 $OH^-$ ions.

23. Identify the effect of temperature on $K_{sp}$ for endothermic dissolution.

    $K_{sp}$ increases with temperature. Higher temperature favors endothermic dissolution process.

24. How does $K_{sp}$ change with temperature for exothermic reactions?

    $K_{sp}$ decreases with temperature. Lower temperature favors exothermic dissolution process.

25. Identify the $K_{sp}$ expression for $Hg_2Cl_2$.

    $K_{sp} = [Hg_2^{2+}][Cl^-]^2$. Dimeric mercury(I) ion has +2 charge with two chlorides.

26. What is $K_{sp}$ for $PbCl_2$ given solubility $s$?

    $K_{sp} = 4s^3$. For $PbCl_2$: $K_{sp} = s(2s)^2 = 4s^3$.

27. Identify the common ion effect in solubility equilibria.

    Reduction in solubility due to a common ion. Adding an ion already present shifts equilibrium toward solid formation.

28. What is the solubility product constant ($K_{sp}$) expression for $AgCl$?

    $K_{sp} = [Ag^+][Cl^-]$. Product of ion concentrations at equilibrium for the saturated solution.

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