What happens to the pH when the concentration of H+ increases?

When the concentration of H+ ions in a solution increases, the pH of that solution decreases. This is based on the pH scale, which is logarithmic in nature. The pH is defined as the negative logarithm of the hydrogen ion concentration:

[ \text{pH} = -\log[H^+] ]

As the concentration of H+ ions rises, the value of ([H^+]) increases, leading to a more negative value for the logarithm and, consequently, a lower pH value. This relationship indicates an increase in acidity.

In contrast, if the concentration of H+ were to decrease, the solution would become less acidic, leading to an increase in pH. The other options do not accurately reflect how pH responds to changes in H+ concentration. The pH does not remain constant when H+ concentration changes, nor does it simply fluctuate without a defined trend related to H+ concentrations. Thus, an increase in H+ directly correlates with a decrease in pH.