Question

(a) What is an indicator? Name three common indicators.
(b) Name the acid-base indicator extracted from lichen.
(c) What colour does the turmeric paper turn when put in an alkaline solution?

Answer 1

(a) Indicators are substances that show a distinct change (colour or odour) simultaneous to a change in concentration of ions such as H⁺ and OH^- ions.
Examples: Methyl orange, phenolphthalein and litmus solution.

(b) A purple dye is extracted from a plant called lichen. This dye is called a litmus solution and is commonly used as an indicator.

(c) When turmeric paper is put into an alkaline solution, it turns red.