chemistry question

Question

If a buffer solution is 0.210 in a weak base (𝐾b=3.8×10−5) and 0.500 M  in its conjugate acid, what is the pH?

Answer 1

Use the Henderson Hasselbalch equation for a basic buffer:

pOH = pKb + log [conjugate acid]/[base]

pKb = -log Kb = 4.42

pOH = 4.42 + log [0.500]/[0.210]

pOH = 4.42 + log 2.38

pOH = 4.42 + 0.38

pOH = 4.80

pH = 14 - pOH

pH = 9.20