Strong acids like hydrochloric acid (HCl) dissociate completely in water, breaking down all molecules into hydrogen (H+) ions and conjugate base ions. Weak acids like hydrofluoric acid (HF) only partially dissociate in water, with some molecules remaining undissociated and some breaking into H+ ions and conjugate base ions. When 10 molecules of the strong acid HCl dissolve in water, all 10 dissociate into 10 H+ ions and 10 Cl- ions, but when 10 molecules of the weak acid HF dissolve, only 1 dissociates while the other 9 remain as HF molecules.

1. S trength of Acids