Chemistry Regents Practice Test 2026 – The All-in-One Guide to Exam Success!

Potassium hydroxide is classified as an Arrhenius base because it contains hydroxide ions (OH-) in its chemical structure. According to the Arrhenius definition, a base is a substance that increases the concentration of hydroxide ions in an aqueous solution. When potassium hydroxide dissolves in water, it dissociates completely into potassium ions (K+) and hydroxide ions (OH-). The presence of these hydroxide ions is what characterizes it as a base under the Arrhenius theory.

In contrast, other choices do not accurately define the classification: The first choice incorrectly associates the behavior of an Arrhenius base with the production of H+ ions, which is characteristic of acids. The third choice is not true because potassium hydroxide does dissociate readily in water, and the fourth choice inaccurately limits the reactivity of potassium hydroxide to reactions with metals only, which is not foundational to its classification as a base. The defining feature that confirms potassium hydroxide's status as an Arrhenius base lies in its production of hydroxide ions in solution.