What is required for a substance to be defined as a base in aqueous solutions?

To define a substance as a base in aqueous solutions, it is essential that it produces OH- ions. Bases are characterized by their ability to accept protons (H+ ions) or donate pairs of valence electrons, a concept rooted in the Brønsted-Lowry and Lewis definitions respectively. When a base dissolves in water, it typically dissociates to release hydroxide ions (OH-), which interact with the hydrogen ions present in the solution, thus increasing the pH and creating an alkaline environment.

The production of OH- ions is a fundamental property that distinguishes bases from acids in aqueous solutions. While acids produce H+ ions, bases are fundamentally identified by their generation of hydroxide ions. This property is crucial not only in understanding the behavior of substances in solutions but also in various chemical reactions, buffer systems, and their roles in biological systems.

In contrast, the other choices do not align with the definition of a base. Producing H+ ions characterizes acids, producing SO4- ions is unrelated to the basicity of a substance, and having a neutral pH indicates neither acidic nor basic properties. Thus, the requirement for a substance to be defined as a base in an aqueous solution centers on its ability to produce