A suitable method for the determination of vitamin C (ascorbic acid, C6H3O6) is a titration with potassium iodate (KIO3). In this reaction, potassium iodate is used as a titrant and when added to an ascorbic acid solution that contains strong acid and potassium iodide (KI), the potassium iodate reacts with potassium iodide, liberating molecular iodine (I2) as shown in the reaction below: [1] KIO3 + 5KI + 6H* → 312 + 6K* + 3H20 During the titration, as long as the solution contains ascorbic acid, the l2 produced in equation I is used up in a rapid reaction with ascorbic acid (equation 2), during which dehydroascorbic acid (C6H6O6) and iodide ion (1) are formed: [2] C6H8O6 + 2 → C6H6O6 + 21 + 2H* Once all the ascorbic acid has been consumed, any excess iodine (1) will remain in solution. This excess iodine reacts with starch, to form an intensely blue colored complex, indicating that the endpoint is reached.

A suitable method for the determination of vitamin C (ascorbic acid, C6H3O6) is a titration with potassium iodate (KIO3). In this reaction, potassium iodate is used as a titrant and when added to an ascorbic acid solution that contains strong acid and potassium iodide (KI), the potassium iodate reacts with potassium iodide, liberating molecular iodine (I2) as shown in the reaction below: [1] KIO3 + 5KI + 6H* → 312 + 6K* + 3H20 During the titration, as long as the solution contains ascorbic acid, the l2 produced in equation I is used up in a rapid reaction with ascorbic acid (equation 2), during which dehydroascorbic acid (C6H6O6) and iodide ion (1) are formed: [2] C6H8O6 + 2 → C6H6O6 + 21 + 2H* Once all the ascorbic acid has been consumed, any excess iodine (1) will remain in solution. This excess iodine reacts with starch, to form an intensely blue colored complex, indicating that the endpoint is reached.

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter13: Titrations In Analytical Chemistry

Section: Chapter Questions

Problem 13.5QAP

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