A chemist mixes 50.0 mL of 0.25 M NH₃(aq) with 30.0 mL of 0.25 M HCl(aq)
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A chemist mixes 50.0 mL of 0.25 M NH₃(aq) with 30.0 mL of 0.25 M HCl(aq). Assume volumes are additive and temperature is 25 °C. The base-dissociation constant for NH₃ is K_b = 1.8 × 10⁻⁵.
(a) Calculate the number of moles of each species present immediately after mixing but before any acid–base reaction occurs.
(b) Determine whether the final solution is a buffer. Support your answer with quantitative evidence based on the stoichiometry of the neutralization reaction.
(c) If the solution is a buffer, calculate its pH. If it is not a buffer, calculate the pH that results from the dominant species present.