Which of the following is a weak acid ?

ANS:A - HF

Among the options provided, HF (hydrofluoric acid) is considered a weak acid. Hydrofluoric acid (HF) is a weak acid because it only partially dissociates into ions when dissolved in water. Specifically, in aqueous solution, HF partially dissociates into hydrogen ions (H⁺) and fluoride ions (F⁻). However, the dissociation is not complete, meaning that only a small fraction of HF molecules ionize, resulting in a relatively low concentration of hydrogen ions in solution. In contrast, HCl (hydrochloric acid), HBr (hydrobromic acid), and HI (hydroiodic acid) are strong acids. They undergo complete dissociation into ions when dissolved in water, resulting in a high concentration of hydrogen ions in solution. So, the correct answer is HF (hydrofluoric acid).