Question

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.

Explain the changes in colour of this indicator which take place during washing and rinsing the shirt.

Answer 1

 When the shirt with a yellow stain of curry is washed with soap, the stain turns reddish brown because soap is basic and turmeric gives a reddish-brown colour when reacts with a base. When rinsed with plenty of water, the reddish-brown stain turns yellow again due to removal soap.