Question

A titration is performed using iodine as the titrant for determining the amount of vitamin C in a sample of lemon juice. A dark blue color appears, then fades rapidly, with the addition of the titrant. Starch is used as the indicator for the reaction.
As the vitamin C concentration is depleted, the dark blue color stabilizes, indicating the endpoint has been reached.
This can be explained by which of the following?

• A. The complex formed during the reaction between the vitamin C and iodine solution has finally turned a dark blue.
• B. The reaction between the starch and the vitamin C formed a complex compound with the iodine.
• C. The vitamin C breaks down into a new compound incorporating starch and enough iodine solution has finally been added to cause the color change.
• D. Once all of the vitamin C has been reacted, the excess iodine is able to react with the starch resulting in the color change seen.

Answer 1

The correct option is A The complex formed during the reaction between the vitamin C and iodine solution has finally turned a dark blue.

An indicator is just to make out difference between the starting and end point.

$⟶$ After the addition of titrant a dark blue colour stabilizes indicating end point it denotes the complex formed during the reaction between Vitamin C and Iodine solution.