f a buffer solution is 0.200 M in a weak acid ( 𝐾a=1.9×10−5) and 0.600 M in its conjugate base, what is the pH?

Answer 1

Let the weak acid be represented by HA

The conjugate base then is A^-

For a buffer, we can use the Henderson Hasselbalch equation:

pH = pKa + log [conj.base] / [acid]

pKa = -log Ka = -log 1.9x10^-5 = 4.72

pH = 4.72 + log (0.600 / 0.200)

pH = 4.72 + 0.48

pH = 5.20