The correct option is (c).
Explanation
Turmeric is a natural acid-base indicator derived from the Curcuma longa plant. Its active component, curcumin, exhibits distinct color changes depending on the pH of the solution it interacts with, specifically distinguishing between acidic/neutral and basic environments.
Statement-wise Analysis:
- Statement 1 is Correct: Turmeric paste does not change its color in acidic or neutral solutions. It retains its natural yellow color when exposed to acids (pH < 7).
- Statement 2 is Incorrect: In basic (alkaline) solutions (pH > 7), turmeric changes its color from yellow to deep red or reddish-brown. It does not turn blue; litmus paper turns blue in basic solutions.
- Statement 3 is Correct: Soap solutions are alkaline (basic) in nature. When soap is applied to a turmeric stain on a cloth, the basic nature of the soap reacts with the turmeric, causing the yellow stain to turn reddish-brown.
Key Takeaway:
Turmeric acts as a natural indicator that remains yellow in acidic and neutral media but turns reddish-brown in basic (alkaline) media.