What is the relationship between pH and [H₃O⁺] concentration?

The relationship between pH and the concentration of hydronium ions ([H₃O⁺]) is quantifiable through the equation pH = -log[H₃O⁺]. This equation illustrates that a decrease in the hydronium ion concentration leads to an increase in pH.

When the pH value rises, it indicates that the solution is becoming less acidic, which corresponds to a lower concentration of hydronium ions. Therefore, as pH increases, the concentration of [H₃O⁺] indeed decreases. This inverse relationship is fundamental to understanding acid-base chemistry in aqueous solutions.

This relationship is not direct, and pH and [H₃O⁺] are not independent of each other. Instead, they exhibit a logarithmic relationship where changes in one affect the other in a specific manner, confirming the chosen answer's correctness.