Answer:
pka of the weak acid = 4.64
Explanation:
pH of solution is calculated by using Henderson - Hasselbalch equation
[tex]pH=pKa+log(\frac{[A^{-} ]}{[HA]} )[/tex] --------------------(i)
[tex]Moles of KOH =\frac{12}{1000} X3.2=0.0384[/tex]
HA + KOH ⇄ HK + H₂O
Initial 0.25 0.0384 0 0
Equm. 0.2116 0 0.0384
From equation (i)
[tex]pKa = pH - log(\frac{[A^{-} ]}{[HA]} )\\\\ =3.9 - log(\frac{0.0384}{0.2116} )\\\\= 3.9 - log (0.18)\\\\= 3.9+0.74\\\\=4.64[/tex]
