Definition of pH
pH is a numerical scale used to specify the acidity or alkalinity of an aqueous solution.
It is defined as the negative base-10 logarithm of the activity (concentration) of hydrogen ions (H⁺):
Hydrogen ion concentration ([H⁺]) is measured in moles per liter (mol/L).
pH Scale
The pH scale typically ranges from 0 to 14, although values can be less than 0 or greater than 14 for very strong acids or bases.
Neutral solution: pH = 7 (e.g., pure water at 25°C).
Acidic solution: pH < 7 (higher concentration of H⁺ ions).
Basic (alkaline) solution: pH > 7 (lower concentration of H⁺ ions).
Importance of pH
Chemical Reactions: pH influences reaction rates and equilibria.
Biological Systems: Enzyme activity and metabolic processes are pH-dependent.
Environmental Science: pH affects water quality and soil chemistry.
Medicine: Blood pH is tightly regulated; deviations can be life-threatening.