Art 6 1 ph theory and measurement

pH is a unit of measure which describes the degree of acidity or alkalinity of a solution. Acidity is defined as the concentration of hydrogen ions [H+] in solution and alkalinity as the concentration of hydroxyl ions [OH-] in solution. As seen above the actual theoretical definition of pH is -Log10 aH+. But, since the activity coefficient (a) for hydrogen (H+) is 1 the practical definition for pH can then be defined as -Log10 [H+]. Below is a chart showing the relationship between pH and the Hydrogen ion concentration.