What is the pH equation?

The correct formulation of the pH equation is indeed based on the concentration of hydrogen ions, represented as [H⁺]. The pH scale measures the acidity or basicity of a solution, and it is defined as the negative logarithm (base 10) of the hydrogen ion concentration. Therefore, the relationship is expressed mathematically as pH = -log[H⁺].

This equation indicates that as the concentration of hydrogen ions increases, the pH value decreases, which corresponds to a more acidic solution. Conversely, a lower concentration of hydrogen ions results in a higher pH value, indicating a more basic (alkaline) solution. This logarithmic relationship allows for a convenient way to express the wide range of hydrogen ion concentrations in solutions, as they can vary greatly, typically from 0.0000001 M (pH = 7) for neutral water to strong acids with much higher concentrations of H⁺.

In this context, other options are not accurate representations of the pH equation. For example, a direct logarithmic function of the hydrogen ion concentration without the negative sign does not provide the expected pH values. Similarly, stating pH as negative concentration or as a log of the reciprocal of hydrogen ion concentration would