What is the pH of water? What does it mean?
pH is one of the most important physical and chemical parameters of aqueous solution. Where the natural phenomena, chemical changes and production processes involved in aqueous solutions are pH dependent, pH measurement is required in the fields of industry, agriculture, medicine, environmental protection and research.
The pH of water is the negative logarithm of the hydrogen ion activity in water, expressed as:
pH = - lg aH +
The pH value is sometimes called the hydrogen ion index. Since the hydrogen ion activity is often small and often inconvenient to use, one of the concepts of pH is used as an indicator of acidity and alkalinity in aqueous solution. Moreover, the negative logarithm of the hydrogen ion activity can be expressed on the order of magnitude of the change in acidity, basicity, which is very convenient for use and is thus obtained:
⑴ neutral aqueous solution, pH = - lg aH + = - lg10-7 = 7
⑵ acidic aqueous solution, pH <7, the smaller the pH value, indicating that the more acidic;
⑶ alkaline aqueous solution, pH> 7, the greater the pH value, that alkaline more strong.