Answer
According to Arrheniu, an acid is a substance that produces $H^+$ ions when added to an aqueous solution, and a base is a substance that produces $OH^-$ ions when added to an aqueous solution.
Work Step by Step
According to Arrheniu, an acid is a substance that produces $H^+$ ions when added to an aqueous solution, and a base is a substance that produces $OH^-$ ions when added to an aqueous solution.