pH - Potential of Hydrogen
The concentration of hydrogen ions is commonly expressed in terms of the pH scale. It represents the ratio of Hydronium ions (H3O) to Hydroxide ions (OH). High pH corresponds to low hydrogen ion concentration and vice versa.
pH varies in the range of 1 to 14. The solution closer to 1 is highly acidic, while the solution closer to 14 is the strong base. A Neutral liquid (Pure water at 25 °C) has pH of 7.
On the basis of the pH value of the solution, it is determined to be either acidic or basic. A pH less than 7 represents an acidic solution and a value higher than 7 is basic or alkaline.