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Class 10
Solutions to CBSE Sample Paper - Science Class 10

Vinay observed that the stain of curry on a white shirt becomes reddish-brown when soap is scrubbed on it, but it turns yellow again when the shirt is washed with plenty of water. What might be the reason for his observation?

(i) Soap is acidic in nature

(ii) Soap is basic in nature 

(iii) Turmeric is a natural indicator which gives reddish tinge in bases

(iv) Turmeric is a natural indicator which gives reddish tinge in acids 

 

(A) i and ii 

(B) ii and iii 

(C) i and iv 

(D) ii and iv 

 

Answer - 

Stain of curry on white cloth-01.jpg

  • Curry makes stain on white shirt (we don’t know the color yet).
    Based on the options, it might be turmeric

  • On adding soap, which is basic, the stain becomes reddish-brown.
    This is because Turmeric is an acid-base indicator , and when it reacts with base, it becomes red

On washing with water, the base dilutes , and washes off. Thus, the turmeric becomes its original yellow color.

Turmeric-Teachoo.jpg

From our options

  • (ii) Soap is basic in nature - is correct
  • (iii) Turmeric is a natural indicator which gives reddish tinge in bases  - is correct

 

So, the correct answer is (b) - (ii) and (iii)

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