Question:
The degree of ionization of a 0.1M bromoacetic acid solution is 0.132. Calculate the pH of the solution and the pKa of bromoacetic acid.
Solution:
Degree of ionization, α = 0.132
Concentration, c = 0.1 M
Thus, the concentration of $\mathrm{H}_{3} \mathrm{O}^{+}=c . a$
= 0.1 × 0.132
= 0.0132
$\mathrm{pH}=-\log \left[\mathrm{H}^{+}\right]$
$=-\log (0.0132)$
$=1.879: 1.88$
Now,
$K_{a}=C \alpha^{2}$
$=0.1 \times(0.132)^{2}$
$K_{a}=.0017$
$p K_{a}=2.75$