Question

Use an ICF (initial-change-final) calculation (using moles, not molarity) to determine the pH and % ionization of 10mL of a solution of (50mL of 0.10M NH₃ + 50mL of 0.10M NH₄NO₃) + 6mL of 0.10M HCl

Answer 1

From the given data,

initial NH3 = 0.1 M x 50 ml = 5 mmol

initial NH4+ = 0.1 M x 50 ml = 5 mmol

Added HCl (change) = 0.1 M x 6 ml = 0.6 mmol

final NH3 = 5.0 - 0.6 = 4.4 mmol

final NH4+ = 5.0 + 0.6 = 5.6 mmol

pH of solution = pKa + log(base/acid)

                       = 10.25 + log(4.4/5.6)

                       = 10.14