Final answer:
HI is classified as an Arrhenius acid because it ionizes in water to release hydrogen ions (H+), increasing the concentration of H+ ions in the solution, which is the defining behavior of an Arrhenius acid.
Step-by-step explanation:
Hydroiodic acid (HI) is classified as an Arrhenius acid because, by definition, an Arrhenius acid is a substance that increases the concentration of hydrogen ions (H+) in aqueous solution. When HI dissolves in water, it ionizes to yield hydrogen ions (H+), which can also be referred to as hydronium ions (H3O+) when they associate with water molecules. This behavior fits the criteria set by Svante Arrhenius, a Swedish chemist, to describe acids and bases. The characteristic chemical equation representing this process shows the addition of H2O to the reactants side, as follows: HI + H2O → H3O+ + I−.
An example to further illustrate this concept is when hydrochloric acid (HCl) dissolves in water, it also releases H+ ions, behaving as an Arrhenius acid. The practical takeaway is that substances like HI and HCl, which produce hydrogen ions when dissolved in water, are recognized as Arrhenius acids. This understanding is crucial in predicting the behavior of acids in chemical reactions, including neutralization, where an acid and a base react to form water and a salt.