A white shirt has a yellow stain of curry. When soap is rubbed on this shirt during washing, the yellow stain turns reddish-brown. On rinsing the shirt with plenty of water, the reddish-brown stain turns yellow again.
(a) Name the natural indicator present in curry stain.
(b) Explain the changes in colour of this indicator which take place during washing and rinsing the shirt.
(c) What is the nature of soap (acidic/basic) as shown by the indicator present in curry stain?
(a) Turmeric.
(b) The yellow stain of curry turns reddish-brown when soap is scrubbed on it because of the fact that soap solution is basic in nature which changes the colour of turmeric in the curry stain to red-brown. This stain turns yellow again when the cloth is rinsed with water because then the basic soap gets removed with water.
(c) Basic.