In terms of hydroxide ions, what defines an alkali?

An alkali is defined as a substance that produces hydroxide ions (OH⁻) when dissolved in water. This property is fundamental to alkalis, as they have the ability to increase the concentration of hydroxide ions in a solution, resulting in characteristic properties such as a slippery feel, a bitter taste, and the ability to neutralize acids.

For example, when sodium hydroxide (NaOH) is dissolved in water, it dissociates into sodium ions (Na⁺) and hydroxide ions (OH⁻). The presence of these hydroxide ions is what gives an alkaline solution its basicity and contributes to its reactivity with acids, forming water and a salt in a neutralization reaction.

The other options pertain to different types of ions that do not define alkalis. Hydrogen ions (H⁺) are associated with acids, not alkalis, as they contribute to the acidic properties of a solution. Sulfate ions (SO₄²⁻) and nitrate ions (NO₃⁻) are common anions associated with various salts and do not specifically relate to the definition of an alkali. Therefore, the definition centered around the generation of hydroxide ions is what establishes an alkali in the