Final answer:
Among the given options, H₂CO₃ (carbonic acid) is the weak acid because it does not dissociate completely in water compared to the other strong acids listed. Option F is correct.
Step-by-step explanation:
The substance that is a weak acid among the given options is H₂CO₃ (carbonic acid). In general, strong acids like HCl, HBr, HI, HNO₃, HClO₄, and H₂SO₄ dissociate completely in water, releasing a high concentration of hydrogen ions (H+). On the other hand, weak acids such as H₂CO₃ partially dissociate in water, releasing fewer hydrogen ions into the solution.
The weak acids tend to have a lower degree of ionization compared to strong acids. Hence, carbonic acid (H₂CO₃) is the correct answer because it doesn't dissociate completely in water and is less strong than sulfuric acid (H₂SO₄), nitric acid (HNO₃), hydrochloric acid (HCl), hydrobromic acid (HBr), perchloric acid (HClO₄), and hydroiodic acid (HI).