If a buffer solution is 0.180 M in a weak base ( 𝐾b=2.9×10−5) and 0.460 M in its conjugate acid, what is the pH?

Answer 1

You can use the Henderson Hasselbalch equation for a basic buffer:

pOH = pKb + log [conj.acid] / [base]

pKb = -log Kb = -log 2.9x10^-5 = 4.54

pOH = 4.54 + log (0.180 / 0.460)

pOH = 4.54 + log 0.391 = 4.54 - 0.407

pOH = 4.13

pH = 14 - 4.13

pH = 9.87