Question

Assertion: In the iodometric titration, starch is used as an indicator.

Reason: Starch is a polysaccharide.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

The correct option is: (b)

Explanation:

Starch (C₆H₁₀O₅)_n is a polysaccharide. It consists of two fractions - one is known as α-amylose and the other is β-amylose or amylopectin. 

In iodimetric and iodometric titrations, starch solution is used as an indicator. It gives blue or violet colour with free iodine. At the end point, the blue or violet colour disappears when iodine is completely changed to iodide.