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

When a strong acid is added to a solution, the pH decreases. This is due to the characteristic behavior of strong acids, which completely dissociate in water to produce hydrogen ions (H⁺). The concentration of these hydrogen ions directly influences the pH of a solution, given that pH is defined as the negative logarithm of the hydrogen ion concentration.

As the concentration of H⁺ ions increases when a strong acid is introduced, the pH value, which ranges from 0 (very acidic) to 14 (very basic), moves downward. For instance, if you have a pH of 7 (neutral) and add a strong acid like hydrochloric acid (HCl), the pH will decrease below 7, indicating a more acidic environment.

The notion that the pH could remain constant, increase, or become neutral does not apply when a strong acid is involved, as these scenarios do not align with the chemical properties of such acids.