Why does a turmeric stain become reddish-brown when soap is applied?
Answer and explanation
Correct answer: Soap is basic
Turmeric contains a natural indicator substance called curcumin. This indicator remains yellow in an acidic or neutral environment but changes to reddish-brown in a basic environment. Soap solution is generally basic because its ingredients produce an alkaline solution in water. Therefore, applying soap to a turmeric stain causes the observed reddish-brown color. Option A gives the reason; the other choices do not describe the indicator reaction.
Frequently asked questions
What is the correct answer to this question?
Soap is basic
Why is this the correct answer?
Turmeric contains a natural indicator substance called curcumin. This indicator remains yellow in an acidic or neutral environment but changes to reddish-brown in a basic environment. Soap solution is generally basic because its ingredients produce an alkaline solution in water. Therefore, applying soap to a turmeric stain causes the observed reddish-brown color. Option A gives the reason; the other choices do not describe the indicator reaction.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
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