Consider the following : The concentration of hydrogen ions in an aqueous solution is expressed by its 1. pH 2. pOH 3. pKa 4. pKw Which of the above is/are correct?

The concentration of hydrogen ions ([H+]) in an aqueous solution is directly expressed by pH, which is defined as the negative logarithm (base 10) of the hydrogen ion concentration. While pH is the primary measure, pOH also expresses this concentration indirectly through the fundamental relationship pH + pOH = pKw (which equals 14 at 25°C). Because the product of [H+] and [OH-] is constant in water (Kw), knowing the pOH allows for the direct calculation of the hydrogen ion concentration. In contrast, pKa is the acid dissociation constant, which describes the strength of an acid rather than the specific ion concentration of a solution, and pKw is the ion product constant of water itself. Therefore, only pH and pOH are used to express the actual concentration of hydrogen ions in a given solution.