pH is equal to the negative logarithm of the hydrogen ion concentration. This is expressed mathematically as: pH = -log[H⁺]
This means that the pH value indicates the concentration of hydrogen ions (H⁺) in a solution. A higher concentration of hydrogen ions results in a lower pH value (more acidic), while a lower concentration of hydrogen ions results in a higher pH value (more alkaline).
Understanding the pH Scale
The pH scale typically ranges from 0 to 14.
- pH 7: Neutral (pure water)
- pH < 7: Acidic (higher concentration of H⁺ ions)
- pH > 7: Alkaline or Basic (lower concentration of H⁺ ions)
The scale is logarithmic, meaning each whole number change represents a tenfold change in hydrogen ion concentration. For example, a solution with a pH of 3 is ten times more acidic than a solution with a pH of 4.
A water source's pH is an important indicator of its acidity or alkalinity. This is because the hydrogen ion activity is a good indicator of the water's overall chemical characteristics. Therefore, measuring pH helps determine the suitability of the water for various purposes, including drinking and irrigation.
