Iodimetric titration is the direct titration with I2 solution. I2 is a weak oxidizing agent and is used to titrate strong reductants.
1. Before the equivalence point, the addition of small amounts of the titrant, I2, transforms it to the colorless iodide ion, I-. After the equivalence point, there is a slight excess of the I2 solution. In the presence of the starch indicator, what color change happens to the mixture? _________________________________
2. Write the net redox reaction representing the reaction between ascorbic acid, C6H8O6, and I2.
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Standardization of a Solution
A 25.00 mL aliquot portion of 0.02420 M C6H8O6 standard solution was transferred into a conical flask. After adding 50 mL H2O, the mixture needed 26.12 mL I2 solution to reach the endpoint.
3. Calculate the number of mmoles of C6H8O6-. ______________ mmoles C6H8O6
4. How many mmoles of I2 reacted with the C6H8O6? __________________ mmoles I2
5. What is the molarity of the I2 solution? _________________ M I2
Analysis of Vitamin C Supplement
The composition of an OTC Vitamin C Supplement is advertised as 350 mg ascorbic acid per tablet.
6. Calculate the number of mmoles of C6H8O6 present in 1 tablet. ________________ mmol
7. How many mL of 0.025 M I2 solution will be needed to titrate a solution that contains 1 dissolved tablet of the OTC drug? _________________ mL
8. Would you recommend diluting the sample before titration? _________________