What do bases do to the free hydrogen ion concentration in water?

Bases decrease the free hydrogen ion concentration in water. When a base is added to water, it dissociates into hydroxide ions (OH⁻) and often reacts with hydrogen ions (H⁺). This reaction reduces the concentration of free hydrogen ions in the solution because the hydroxide ions can combine with the hydrogen ions to form water (H₂O). As a result, the overall acidity of the solution decreases, which is reflected in a higher pH value. In essence, the introduction of a base neutralizes some of the hydrogen ions, leading to a decrease in their concentration and thus creating a more basic or alkaline environment.