What defines a base?

A base is defined as a substance that, when dissolved in water, increases the concentration of hydroxide ions (OH-) in the solution, leading to a pH greater than 7. This characteristic makes bases alkaline in nature.

When discussing the pH scale, values below 7 indicate acidity, while values above 7 indicate basicity. Therefore, the release of hydroxide ions is a fundamental property of bases that contributes to their higher pH levels, distinguishing them from neutral substances and acids.

The other options, while they contain elements related to bases, do not fully encompass the primary defining feature of a base. A compound that neutralizes acids is a characteristic associated with bases, but it does not precisely define what a base is, as not all bases necessarily neutralize acids. A substance with a pH of 7 is neutral and not indicative of basicity. Lastly, the formation of salts when bases react with acids is a consequence of neutralization reactions, rather than a definition of what constitutes a base. Thus, the definition focusing on hydroxide ion liberation and pH is the most accurate interpretation of a base.