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A titration is performed using iodine as the titrant to determine the amount of vitamin C in a sample of lemon juice. A dark blue color appears and 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.

Which of the following explains this phenomenon?


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


The reaction between the starch and the vitamin C formed a complex compound with the iodine.


The vitamin C breaks down into a new compound, incorporating starch, and enough iodine solution has finally been added to cause the color change.


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.

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