pH is the measure of what?

The correct answer is that pH measures hydrogen ion concentration. pH is defined as the negative logarithm of the hydrogen ion concentration in a solution. It reflects how acidic or basic a solution is, with lower pH values indicating higher acidity (and thus higher concentrations of hydrogen ions), while higher pH values indicate greater basicity or alkalinity (and lower concentrations of hydrogen ions).

Understanding pH is essential in water treatment processes, as it affects chemical reactions, microbial activity, and the solubility of minerals and metals in water. The balance of hydrogen ions in water can influence the overall quality of the water and its suitability for various uses, such as drinking, agriculture, and industrial processes.