What term describes the decrease in the concentration of ions per unit volume when mixing an acid or base with water?

The term that describes the decrease in the concentration of ions per unit volume when mixing an acid or base with water is “dilution.” Dilution involves adding a solvent, usually water, to a concentrated solution, resulting in a decrease in the concentration of solute particles (ions) per unit volume. This process does not alter the total number of ions present but disperses them in a larger volume, reducing their concentration. Dilution is a common technique used to control the strength of acids and bases for various applications, allowing for safer handling and precise adjustments of solution concentrations.