Chemistry - Ionic Equilibrium Question with Solution | TestHub

(A) Pure water is neutral: $[{\mathrm{H}}^{+}]$ = √$K_w$ = $10^{-6}$, pH = 6.

(B) NaCN is a salt of a strong base and weak acid: $K_h$ = $10^{-14}/10^{-9}$ = $10^{-5}$, $[{\mathrm{OH}}^{-}]$ = √($10^{-5}$ × 0.1) = $10^{-3}$, pOH = 3, so pH = 11.

(C) ${\mathrm{NH}}_4\mathrm{Cl}$: $K_h$ = $10^{-9}$, $[{\mathrm{H}}^{+}]$ = √($10^{-9}$ × 0.1) = $10^{-5}$, pH = 5.

(D) $K_a(\mathrm{C}{\mathrm{H}}_3\mathrm{COOH})=K_b(\mathrm{N}{\mathrm{H}}_4\mathrm{OH})$, so the solution is neutral: pH = 7.

Maximum pH is 11: (B).

Answer: (B).