What characterizes an alkaline solution?

An alkaline solution is characterized by an excess of hydroxide ions (OH-). This means that the solution has a higher concentration of OH- ions than hydrogen ions (H+), resulting in a pH greater than 7. In basic or alkaline solutions, these hydroxide ions contribute to the solution's basic properties, which include the ability to neutralize acids.

When an alkali, such as sodium hydroxide or potassium hydroxide, is dissolved in water, it dissociates to produce hydroxide ions. This increase in hydroxide ions raises the pH of the solution, making it alkaline.

While an alkaline solution can also conduct electricity due to the presence of these ions, the defining characteristic is specifically the excess of hydroxide ions. The other options provided do not accurately describe this fundamental property of alkalinity.