Why chloroacetic acid has lower pKa value than acetic acid?
Chloroacetic acid is strong acid then acetic acid because in chloro acetic acid, chlorine atom attached to acetic acid due to its high electronegativity weakens the O-H bond and Also stabilizes the anion making H+ to go in easy maner but in case of acetic acid it is hydrogen hence it is not possible to donate H+.
PKa = - log10 Ka
PKa value depends upon the strength of acid. If acid is strong than PKa value would be less and vice versa. So PKa-acetic acid is 4.23 and chloroacetic acid is 2.3.