pH measures the acidity or basicity (alkalinity) of an aqueous solution by quantifying the concentration of hydrogen ions (H⁺) present. It is defined as the negative logarithm of the hydrogen ion concentration: pH=−log[H+]\text{pH}=-\log[H^+]pH=−log[H+]. This means that lower pH values indicate higher acidity (more hydrogen ions), and higher pH values indicate greater alkalinity (fewer hydrogen ions, more hydroxyl ions)
. The pH scale ranges from 0 to 14, with 7 being neutral (pure water). Values below 7 signify acidic solutions, and values above 7 signify basic or alkaline solutions. Each unit change in pH represents a tenfold change in hydrogen ion concentration, so a solution with pH 5 is ten times more acidic than one with pH 6
. pH is an important chemical indicator used in many fields, including environmental science, chemistry, biology, and industry, to assess water quality, chemical changes, and product quality
. In summary, pH measures how acidic or basic a solution is by indicating the relative concentration of free hydrogen ions in that solution.
