Question

A boy has a thick paste of turmeric. On adding this paste to hydrochloric acid and aqueous solution of sodium hydroxide separately, what colour(s) would he observe?
1. yellow in both cases
2. Yellow in hydrochloric acid and red in sodium hydroxide
3. Pink in hydrochloric acid and blue in sodium hydroxide
4. Blue in hydrochloric acid and red in sodium hydroxide

Answer 1

Correct Answer - Option 2 : Yellow in hydrochloric acid and red in sodium hydroxide

Concept:

Acid and Base

Acid	Base
Acids are sour in taste.	Bases are bitter in taste and have a soapy feel.
Acids are present in sour fruits, vinegar, toilet cleaner, etc.	Bases are present in neem, clove, soaps, etc.
Acids turn blue litmus paper to red.	Bases turn litmus paper from red to blue.

Indicators

• The indicators are chemicals or natural substances which change their colour in presence of acid or base. 
• Litmus paper is an indicator that is obtained from lichens. 
• Some indicators and their colour change are given in the table below:

Indicator	Colour Change in Acidic Solution	Colour Change in Basic Solution
Phenolphthalein	Colourless	Pink
Methyl Orange	Red or Orange	Yellow
Litmus Paper	Red	Blue
Turmeric	Yellow	Red
China Rose	Dark pink	Green

Explanation:

• Turmeric is a natural indicator. 
• It remains yellow in acidic solution and turns red in basic solution. 
• This property of turmeric is also used in painting. 
• Hydrochloric acid is an acid hence turmeric will remain yellow in that solution. 
• Sodium hydroxide is the base, so turmeric will turn red in the sodium hydroxide solution. 

So, the correct option is 'Yellow in hydrochloric acid and red in sodium hydroxide.'