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

Answer:

(a) An indicator is a ‘dye’ that changes colour when it is put in an acid or a base. The three most common indicators are: Litmus, Methyl orange and Phenolphthalein. (b) Litmus. (c Red

Answer 2

Explanation:

(a) Indicators:

• The substance which determines whether the solution is a base or acid is called indicator. It changes colour or smell or taste to indicate whether the solution is a base or acid.  
• The three common indicator includes methyl orange, phenolphthalein, and litmus paper.

(b) Acid-base indicator:

• Litmus paper is the indicator from the lichens. Lichens are organisms which are found in cyanobacteria and algae which comes in various colours.
• The litmus paper is manufactured in various colours and water dissolvable paper which is widely used as acid-base indicator.

(c) Turmeric paper:

• When turmeric paper is added to alkaline solution (base), then reddish brown colour.
• This paper is yellow in colour. This is a natural indicator. When it is added to acid there is no change in the colour which means it is acidic in nature.