Question
For which of the following salts would the relationship between molar solubility, \(s\), in mol/L, and the value of \(K_{sp}\) be represented by the equation \(K_{sp}=4s^3\) ?
A \(PbCO_3\)
B \(Mg_3(PO_4)_2\)
C \(Ag_2SO_4\)
D \(MnS\)
▶️Answer/Explanation
Ans:C
\(Ag_2SO_4\) dissolves to form \(2Ag^+\)(aq) ions and 1 \(SO_4^{2−}\)(aq) ion. Letting s represent the molar solubility of \(Ag_2SO_4\), the Ksp expression for \(Ag_2SO_4\) is \(K_{sp}=[Ag^+]^{2}[SO_4^{2−}]=(2s)^2(s)=4s^3\).
Question
\(Hg_2I_2\)(s)⇄\(Hg_2^{2+}(aq)+2 I^−(aq)\) \(K_{sp}=[Hg_2^{2+}][I^−]^2\)
A saturated solution of \(Hg_2I_2\) is at equilibrium at 25°C as represented by the equation above. If \([I^−]=4.6×10^{−10}\) M at equilibrium, which of the following gives the correct molar solubility, S, and \(K_{sp}\) for \(Hg_2I_2\) ?
A \(S=4.6×10^{−10}\) M; \(K_{sp}=(2.3×10^{−10})(4.6×10^{−10})^2\)
B \(S=4.6×10^{−10}\)M; \(K_{sp}=(4.6×10^{−10})(9.2×10^{−10})^2\)
C \(S=2.3×10^{−10}\)M; \(K_{sp}=(2.3×10^{−10})(4.6×10−10)^2\)
D \(S=2.3×10^{−10}\)M; \(K_{sp}=(4.6×10^{−10})(9.2×10^{−10})^2\)
▶️Answer/Explanation
Ans:C
Based on the stoichiometry of the reaction, \(S=[Hg_2^{2+}]=\frac{[I^−]}{2}\) . Therefore, \(S=2.3×10^{−10}\)M; \(K_{sp}=(2.3×10^{−10})(4.6×10−10)^2\).
Question
\(AgI\)(s)⇄\(Ag^+(aq)+I^−(aq)\) \(K_{sp}=8.3×10^{−17}\) at298K
The dissolution of \(AgI\) is represented above. Which of the following shows the mathematical relationship between the molar solubility, \(S\), and the \(K_{sp}\) of \(AgI\) at 298K ?
A \(S=8.3×10^{−17}mol/L\)
B \(S=(\frac{8.3×10^{−17}}{2})mol/L\)
C \(S=\sqrt{8.3\times10^{-17}}mol/L\)
D \(S=2\sqrt{8.3\times10^{-17}}mol/L\)
▶️Answer/Explanation
Ans:C
Since \(AgI\) dissociates to form one mole of \(Ag^+\)(aq) and one mole of \(I^−\)(aq), \(K_{sp}=[Ag^+][I^−]=8.3×10^{−17}\) and the molar solubility of \(AgI =[Ag^+] =[I^−] =\sqrt{8.3\times10^{-17}}mol/L\).
Question
Which of the following best helps to explain why the value of \(\Delta H^{\circ}\) for the dissolving of \(CaF_2\) in water is positive?
(A)\( CaF_{2}(s)\) is insoluble in water.
(B) \(CaF_{2}(s)\) dissolves in water to form \(CaF_{2}\)(aq) particles.
(C) \(Ca^{2+}\) ions have very strong ion-ion interactions with F – ions in the crystal lattice.
(D) \(Ca^{2+}\) ions have very strong ion-dipole interactions with water molecules in the solution.
▶️Answer/Explanation
Ans:C
Question
Based on the Ksp values in the table above, a saturated solution of which of the following compounds has the highest \({cl ^-}\) ?
(A) \(PbCl_{2}\)
(B) CuCl
(C) AgCl
(D) \(Hg_{2}Cl_{2}\)
▶️Answer/Explanation
Ans:B