According to Arrhenius theory, what is an acid?

According to Arrhenius theory, an acid is defined specifically as any substance that ionizes in water to produce hydrogen ions (H⁺). This definition is based on the behavior of acids in aqueous solutions, where they increase the concentration of hydrogen ions.

For example, when hydrochloric acid (HCl) is dissolved in water, it dissociates into H⁺ ions and chloride ions (Cl⁻). This increase in hydrogen ions is what contributes to the acidic properties of the solution. Therefore, the identification of acids based on their ability to release H⁺ in water aligns perfectly with Arrhenius's theory.

Understanding this concept is crucial in analytical chemistry, as it underpins many acid-base reactions and the examination of solution characteristics.