Which one of the following is the correct sequence of change in colour

Which one of the following is the correct sequence of change in colours when a turmeric stain on white clothes is scrubbed by soap and then washed with water ?

Yellow – pink – blue

Yellow – reddish brown – yellow

Yellow – reddish brown – blue

Yellow – blue – pink

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC NDA-2 – 2020

Download PDF Attempt Online

The correct answer is (B) Yellow – reddish brown – yellow.

Turmeric is a natural acid-base indicator. Its original colour is yellow. In acidic or neutral solutions, it remains yellow. In basic (alkaline) solutions, it turns reddish-brown. Soap solution is basic. Therefore, when a turmeric stain (yellow) on white clothes is scrubbed with soap, it turns reddish-brown. When the cloth is then washed with plain water, which is usually neutral or slightly acidic due to dissolved CO2, the basic soap is rinsed away, and the turmeric indicator returns to its yellow colour.

Other indicators change colours differently in acidic and basic media. For example, litmus paper is red in acid and blue in base; phenolphthalein is colourless in acid and pink in base. Turmeric’s characteristic change from yellow to reddish-brown is a common demonstration of its indicator property.

Join Our Telegram Channel

More similar MCQ questions for Exam preparation:-