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Thread: Chemistry problem.

  1. #1 Chemistry problem. 
    New Member
    Join Date
    Sep 2006
    I need to find how much ascorbic acid is in a Vitamin C Tablet. I got mass of tablet is .149g (given) and the volume of the amount of KIO3 (dilluted with water to have a molarity of .010, provides the Iodate reaction) titrant used was 23.4mL (given). Mass of Ascorbic acid is 176.13g/mol. How in the world do I go about a problem like this?

    Thanks for any help!

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  3. #2  
    Forum Freshman César's Avatar
    Join Date
    Sep 2006
    Spain, Europe
    When you say that the solution provides the iodate reaction I will interpret that the dissolved tablet is in a strong acid media and there is presence of KI, which are the standard conditions for the titration of ascorbic acid. Thus we have the following reactions taking place:

    1. Formation of I2

    KIO3 + 5KI + 6H+ <-> 3I2 + 6K+ + 3H2O

    2. Oxydation of ascorbic acid

    C6H8O6 + I2 <-> C6H6O6 + 2I- + 2H+

    Hence for every mol of KIO3 consumed you have detected three moles of ascorbic acid. From the data given in the problem you can easily calculate the number of moles of ascorbic acid present in the tablet, the weight and the percentage of vitamine C in the tablet.

    Should you have any problem, just whistle.

    Best regards,


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