What defines an alkali in terms of water solubility?

An alkali is defined as a specific type of base that is soluble in water. When a base dissolves in water, it produces hydroxide ions (OH⁻), which is a characteristic behavior of alkalis. This solubility allows them to readily participate in chemical reactions in aqueous solutions and interact with acids, leading to neutralization reactions that produce water and a salt.

The definition of alkalis also includes their ability to increase the pH of aqueous solutions, contributing to basicity. Consequently, it is this water solubility that distinguishes alkalis from other bases that may not dissolve in water, making the identification of alkalis based on their solubility in water crucial for understanding their chemical behavior and reactions.