Question

A yellow stain of curry on a white clothe turns reddish-brown when it comes in contact with soap. Why does this happen?

• A. Soap is basic in nature
• B. Due to the presence of water
• C. Neutral solution
• D. Soap is acidic in nature

Answer 1

The correct option is A

Soap is basic in nature

Part 1: Explanation of correct option

Option A

1. Turmeric is said as an indicator since it turns scarlet in basic conditions and yellow in neutral or acidic ones.
2. Because soap is basic in nature, it turns reddish brown after scrubbing the stain, and when water is added, it turns yellow because water is neutral in nature.

Part 2: Explanation for incorrect options

Option B.

Water helps remove the soap lather and dirt, but it does not change the colour of the stain

Option C.

A neutral solution is neither basic nor acidic. A neutral solution does not change the colour.

Option D.

The soap contains sodium salts. Sodium salts are basic in nature

Therefore, soap is a base that changes the turmeric colour to reddish-brown on washing