Ionization of an acid of form (HA) can be represented as follows
HA ↔ H+ + A-
Ka = [tex] \frac{[H+][A-]}{[HA]} [/tex]
Now, initial conc. of HA = 0.12 M
Of these, 2.3 % got ionized.
∴ [H+] = [A-] = 0.12 X 0.023 = 0.00276 M
Thus [HA] left after ionization = 0.12 - 0.00276 = 0.11724 M
Now Ka = [tex] \frac{(0.00276 )^2}{0.11724} [/tex] = 6.497 x 10^-5
