Which one of the following is the weakest acid?
HF
The hydrogen-fluorine bonding (Hydrogen-bond) in HF is relatively strong so it only partially dissociates in water, making it a weak acid means H+ ions are not free to go into the solution thus limiting the strength of HF in water. The hydrogen-chlorine bond (Hydrogen-bond) in HCl is very weak, allowing it to completely dissociate in water thus it qualifies as a strong acid.