Question

1.)An ammonia/ammonium buffer solution contains 0.35 M NH3 and 0.72 M NH4+. The Kb value of ammonia is 1.8×10−5. Calculate the pH of this buffer.

2.) Nitrous acid has a Ka of 4.5×10−4. What is the pH of a buffer solution containing 0.15 M HNO2 and 0.20 M NO−2?

3.) Acetic acid has a Ka of 1.8×10−5.
What is the pH of a buffer solution containing 0.14 M HC2H3O2 (acetic acid) and 0.20 M C2H3O2−?

Answer 1

1. Use the Henderson-Hasselbalch equation. KaKb = Kw and you get Ka from that and pKa follows.

2. Ditto for 2.

3. Ditto for 3.