What happens to the pH of a solution when a strong acid is added?

When a strong acid is added to a solution, it completely dissociates in water, releasing a high concentration of hydrogen ions (H⁺). The pH of a solution is a measure of the hydrogen ion concentration; specifically, it is defined as the negative logarithm of the hydrogen ion concentration. As the concentration of hydrogen ions increases due to the addition of the strong acid, the value of the pH decreases.

For example, if you add hydrochloric acid (HCl), which is a common strong acid, it dissociates fully to release H⁺ ions. This increase in hydrogen ion concentration directly contributes to lowering the pH value, meaning that the solution becomes more acidic. Therefore, the pH does decrease as a direct result of the enhanced hydrogen ion concentration from the acid. Understanding the relationship between acid dissociation and pH is fundamental in acid-base chemistry and helps explain numerous chemical behaviors in various solutions.