The pH scale ranges from 0 to 14. On this scale, pH 7 is considered neutral, below 7 acidic and above 7 basic. Farther from 7, more acidic or basic the solution is.
The sum of pH and pOH of any aqueous solution remains constant. Therefore, when one increases the other decreases.
pH + pOH = 14
pH of Some Common Acids and Bases
pH of a solution can be determined by using proper indicator or with the help of a pH meter. The latter is a device which gives accurate value of pH.
Universal Indicator / pH paper
It is a mixture of a number of indicators. It shows a specific colour at a given pH. A colour guide is provided with the bottle of the indicator or the strips of paper impregnated with it which are called pH paper strips. The test solution is tested with a drop of the universal indicator, or a drop of the test solution is put on pH paper.
The colour of the solution on the pH paper is compared with the colour chart/guard and pH is read from it. The pH values thus obtained are only approximate values.