[AL CHEM] p Ka

Given the literature p Ka values(acid dissociation constant) of four weak acids:

p Ka of ethanoic acid is 4.75
p Ka of chloroethanoic acid is 2.86
p Ka of methanoic acid is 3.75
p Ka of benzoic acid is 4.21

arrange the four acids in descending order of acid strength and explain the difference of their acid strength.