Question

What is an acid base Indicator?

Answer 1

1. A qualitative method applied to determine the unknown concentration of acid and base with the help of a known concentration of acid compound or base compound is called an acid-base titration.
2. The completion of the reaction between the two substances, i.e., the endpoint is indicated by a substance that changes colour at this point, is called an indicator.
3. Indicators are used to detect whether the product is acidic or basic.
4. An acid-base indicator possesses one colour in an acidic medium and a different colour in an alkaline medium.
5. In fact, the colour of the indicator depends upon the pH of the solution.
6. The colour change does not take place at a definite pH but occurs in a range of pH called pH range or colour change interval of the indicator.
7. Some common acid-base indicators are listed below :

Indicator	pH Range	Colour
		Acidic indicator	Basic indicator
Methyl violet	0-1.8	Yellow	Violet
Methyl orange	3.1-4.5	Red	Yellow
Litmus	5-8	Red	Blue
Phenol red	6.8-8.4	Yellow	Pink
Phenolphthalein	8-10	Colour less	Pink