C₆H₈O₆(aq) + I₃⁻(aq) + H₂O(l) → C₆H₆O₆(aq) + 3I⁻(aq) + 2H⁺(aq) The titration is carried out in the presence of starch, which forms a dark blue complex with the excess iodine when the endpoint is reached. You are testing a new multivitamin pill for its vitamin C content. One pill weighing 0.763 g is dissolved in dilute acid and titrated with 0.0236 M I₃⁻ solution, requiring 28.3 mL to reach the endpoint. Calculate the percent by mass of vitamin C in the pill.
Vitamin C (ascorbic acid, C₆H₈O₆, 176.12 g/mol) can be measured by redox titration with iodine solution. Iodine is reduced to iodide ion, while ascorbic acid is oxidized to dehydroascorbic acid (C₆H₆O₆). The iodine solution is usually made in the presence of iodide ion, forming the more stable triiodide ion, I₃⁻, giving the following overall reaction
C₆H₈O₆(aq) + I₃⁻(aq) + H₂O(l) → C₆H₆O₆(aq) + 3I⁻(aq) + 2H⁺(aq)
The titration is carried out in the presence of starch, which forms a dark blue complex with the excess iodine when the endpoint is reached. You are testing a new multivitamin pill for its vitamin C content. One pill weighing 0.763 g is dissolved in dilute acid and titrated with 0.0236 M I₃⁻ solution, requiring 28.3 mL to reach the endpoint.
Calculate the percent by mass of vitamin C in the pill.
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