Before any titrant is introduced, 50.0 mL of 0.0750 M aqueous ammonia, NH₃(aq)
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
Before any titrant is introduced, 50.0 mL of 0.0750 M aqueous ammonia, NH₃(aq), is the analyte solution in a burette titration experiment. The base-dissociation constant of ammonia at 25 °C is K_b = 1.8 × 10⁻⁵.
(a) Write the balanced chemical equation that shows the reaction of ammonia with water in this solution.
(b) Set up an ICE (Initial–Change–Equilibrium) representation for the equilibrium in part (a) using a variable x to denote the change in concentration.
(c) Using the information above, calculate the initial pH of the ammonia solution before any titrant is added. Show all reasoning, including any approximations you employ.
(d) Calculate the percent ionization of ammonia under these conditions and comment on whether your approximation in part (c) is justified.