Boojho took some grains of boiled rice in test tube ‘A’ and Paheli took boiled and chewed rice in test tube ‘B’. Both of them poured 1 – 2 drops of iodine solution into the test tube and observed the colour change.

What colour change would they have observed? Give reasons for your answer. [3 marks]

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Solution

Due to the presence of starch in rice, the colour of the rice upon addition of iodine solution changes to blue-black. (1 mark)

However, as soon as the starch gets digested by the saliva, the solution starts turning pink. Since test tube B had chewed rice which contains saliva, the starch gets digested, imparting the pink colour. (1 mark)

So the colour of test tube 'B' changes to pink whereas test tube 'A' remains blue-black. (1 mark)

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Similar questions

Q. Boojho took some grains of boiled rice in test tube 'A', and Paheli took boiled and chewed rice in test tube 'B'. Both of them poured 1 – 2 drops of iodine solution into the test tube and observed the colour change. What colour change would they have observed? Give reasons for your answer.

Question 20
Boojho took some grains of boiled rice in test tube ‘A’ and Paheli took boiled and chewed rice in test tube ‘B’. Both of them poured 1 - 2 drops of iodine solution into the test tube and observed the colour change. What colour change would they have observed? Give reasons for your answer.

Q. Case: Observe the image given below. There are two test tubes (i) and (ii). Test tube (i) contains a starch solution, while test tube (ii) contains starch solution and saliva. Both the test tubes are kept undisturbed for about 20 min. Later, dilute iodine solution (brown in colour) was added to both the test tubes.

We have two test tubes here, X and Y. X contains boiled rice and Y contains boiled rice that has been completely chewed on. Which one is more likely to turn blue-black on adding an iodine solution?

[0.8 Mark]

Option	Test tube (i)	Test tube (ii)
A.	Blue-black	Brown
B.	Brown	Blue-black
C.	Blue-black	Blue-black
D.	Brown	Brown

[0.8 Mark]

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