Question

why CH3COOH is weaker acid compared to HCL, though it has four H - atoms

Answer 1

Acetic acid is CH3COOH
we have to see the no. of atoms in the carboxylic acid functional group.CH3 is a homologous series.
so, COOH. this doesn't ionize completely in water . so it is a weak acid 

Answer 2

Hey

CH3COOH is a naturally occurring acid which makes it weak in nature as compared to HCl which is a mineral acid.

Hope it helps #))