A pH 9.56 buffer was prepared by mixing 2.00 moles of ammonia (Kb for ammonia is 1.8 × 10^-5) and 1.00 mol of ammonium chloride in water to form a solution with a volume of 1.00 L. To a 200.0 mL aliquot of this solution was added 10.0 mL of 10.0 M sodium hydroxide. What was the resulting pH?

Question

Quizplus · Accepted Answer

The addition of NaOH to the buffer will increase the pH slightly. The buffer initially has a pH of 9.56. Adding a strong base like NaOH will convert some NH4+ to NH3, increasing the pH. Calculating the new concentrations and using the Henderson-Hasselbalch equation, the pH is approximately 9.95.

A PH 956 Buffer Was Prepared by Mixing 2