12. In a solution, when the concentrations of a weakacid and its conjugate base are equal,….

[A] the system is not at equilibrium

[B] the -log of the [H⁺] and the -log of theK_a are equal

[C] the buffering capacity is significantly decreased

[D] the buffering capacity is significantly increased

[E] All of the above are true.

13. The concentration of iodide ions in a saturated solution oflead (II) iodide is ________ M.

The solubility product constant of PbI₂ is 1.4 x10^-8.

[A] 1.4 x 10^-8 [B] 1.5 x 10^-3 [C] 3.5 x10^-9 [D] 3.8 x 10^-4 [E] 3.0 x10^-3

14. The solubility of lead (II) chloride (PbCl₂) is1.6 x 10^-2 M. What is the K_sp ofPbCl₂?

   [A] 4.1 x 10^-6 [B] 1.6 x 10^-5[C] 3.1 x 10^-7 [D] 5.0 x 10^-4 [E] 1.6 x10^-2

  15. The solubility of manganese (II) hydroxide(Mn(OH)₂) is 2.2 x 10^-5 M. What is theK_sp of

   Mn(OH)₂?

[A] 2.2 x 10^-5 [B] 2.1 x 10^-14 [C] 1.1 x10^-14 [D] 4.8 x 10^-10 [E] 4.3 x10^-14

16. Which of these expressions correctly expresses thesolubility-product constant for

Ag₃PO₄ in water?

[A] [Ag][PO₄] [B][Ag⁺][PO₄^3−] [C][Ag⁺]³[PO₄^3−]

   [D][Ag⁺][PO₄^3−]³ [E][Ag⁺]³[PO₄^3−]³

  17. A solution of NaF is added dropwise to asolution that is 0.0166 M in Ba²⁺. When the

   concentration of F^- exceeds ________ M,BaF₂ will precipitate. Neglect volume changes.

For BaF₂, K_sp = 1.7 â‹… 10^-6.

[A] 1.0 x 10^-2 [B] 1.0 x 10^-4 [C] 5.1 x10^-5 [D] 2.5 x 10^-3 [E] 2.8 x10^-8

18. A solution contains 2.3 x 10^-4 M Ag⁺and NaI solution is being added drop wise. What

   is the minimum concentration of I^- tobegin precipitation of AgI? Ksp (AgI)= 8.3 x 10^-17

   [A] 8.32 x10^-17 M [B] 2.51 x10^-17 M [C] 3.01 x 10^-15

   [D] 3.51 x 10^-14 M [E] 3.61 x10^-13 M