According to the Arrhenius definition, what does a base do?

The Arrhenius definition characterizes a base as a substance that increases the concentration of hydroxide ions (OH-) in an aqueous solution. When a base is dissolved in water, it dissociates to release these hydroxide ions, which then enhances the alkalinity of the solution. This characteristic is a fundamental aspect of how bases modify the properties of solutions, distinguishing them from acids, which, according to the same definition, increase the concentration of hydrogen ions (H+) in solution.

The other aspects mentioned, such as reducing acidity or neutralizing acids, relate to the broader effects and reactions that bases can have but do not stem directly from the Arrhenius definition of a base. The concept of acidity reduction or neutralization involves more complex interactions and does not define what a base is in terms of hydroxide ion production. Thus, the core function of a base, according to Arrhenius, is specifically to increase the hydroxide ion levels in a solution.