Iodimetric Titration of Vitamin C

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Iodimetric Titration of Vitamin C
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Directions

• Dissolve two tablets in 60 mL of 0.3 M H2SO4.
• Add 2 g of solid KI and 50.00 mL of standard
  KIO3.

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• 60 mL 0.3 M H2SO4.
• 2 g of KI.
• 50.00 mL of standard KIO3.
• I2 I(-1) ?I(-1)3

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• Then titrate with standard thiosulfate
• until the solution has a (pale blue) color.
• I(-1) 3 2S2O(-2) 3 ? 3I(-1)
  Tetrathionate

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While Titration

• Add 2 mL of starch indicator just before the end
  point.

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• Q why we using back titration in this
  experiment ?

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• A because the end point is clearer than the end
  point of the direct titration.