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17 Additional Aspects of Solutions to Exercises Aqueous Equilibria 17.14 (a) For a generic weak base B, Kb = [B] . If an external source of HB+ such as is added to a solution of B(aq), increases, decreasing [OH⁻] and increasing [B], effectively suppressing the ionization (hydrolysis) of B. (b) 17.15 Analyze/Plan. Follow the logic in Sample Exercise 17.1. (a) C₂H₅COOH(aq) 1L + i 0.085 M 0.060 M -x +x +x e (0.085 x) M (0.060 + x) M Assume is small compared to 0.060 and 0.085. Check. Since the extent of ionization of a weak acid or base is suppressed by the presence of a conjugate salt, the 5% rule usually holds true in buffer solutions. (b) (CH₃)₃N(aq) 1L + (aq) i 0.075 M 0.10 M -x +x +x e (0.075 M +xM = 4.8 10⁻⁵ = [OH⁻], pOH = 4.32, pH = 14.00 - 4.32 = 9.68 Check. In a buffer, if [conj. acid] > [conj. base], pH of the conj. acid. In this buffer, of is 9.81. > [(CH₃)₃N] and pH = 9.68, less than 9.81. (c) mol = M X L; mol = 0.15 M 0.0500 L = 7.5 mol mol = 0.20 M 0.0500 L = 0.010 mol CH₃COOH(aq) (aq) + i 7.5 mol 0 0.010 mol -x +x +x e (7.5 -x) mol +x mol (0.010 + mol [CH₃COOH(aq) = mol/0.1000 L; = (0.010 + mol/0.1000 L 506