Leaving Certification Chemistry Practice Exam 2026 – Comprehensive Test Prep

An Arrhenius base is specifically defined as a substance that increases the concentration of hydroxide ions (OH⁻) when dissolved in water. This characteristic is essential to the Arrhenius theory of acids and bases, which states that acids are substances that produce hydrogen ions (H⁺), while bases produce hydroxide ions in aqueous solutions.

When an Arrhenius base dissolves in water, it dissociates or breaks apart, releasing hydroxide ions into the solution. This process is what makes the solution basic, typically resulting in a higher pH. Understanding this concept is critical because it distinguishes Arrhenius bases from other types of bases, such as Bronsted-Lowry bases, which focus on the ability to accept protons. The focus on hydroxide ion production is what specifically correlates to the Arrhenius definition.

In contrast to other choices, such as a substance that dissociates to form hydrogen ions, donates protons, or has a low pH, these descriptions do not accurately capture the defining characteristics of what constitutes an Arrhenius base. The key focus is upon the presence of hydroxide ions in the solution, which is the critical point that comprehensively encapsulates the definition of an Arr