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Homework Help: Determination of Vitamin C

  1. Sep 1, 2017 #1
    1. The problem statement, all variables and given/known data
    Titration:
    Volume of orange juice: 20.00 mL
    Final diluted volume: orange juice + 150mL of deionised water: 170 mL
    Standard Iodine solution concentration: 0.005 mol L-1
    Amount of Iodine used: 26.2mL

    2. Relevant equations
    Is this equation right?

    (Concentration of Iodine Solution * Volume of Iodine used) * (Diluted Volume/Volume of orange juice) * Mass of ascorbic acid * 1000 to get from g/100mL to mg/100mL

    3. The attempt at a solution

    (0.005*0.0262)*(170/20)*176.12*1000

    196.10962

    I feel like there might be something wrong with the equation I am using. Any help would be greatly appreciated
     
  2. jcsd
  3. Sep 1, 2017 #2

    Borek

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    Staff: Mentor

    Instead of using an "equation" why don't you try to just follow stoichiometry and dilution? That's the only sure method of doing every titration problem, no matter if you were given some equation to use, or not.

    Start by writing the reaction equation.
     
  4. Sep 1, 2017 #3

    tech99

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    Gold Member

    You need to use concentration of Ascorbic Acid rather than mass, as you cannot mix up grammes and mols.
    You also need an equals sign.
    And you may need a factor like 2 or 3 somewhere which you will find from the chemical reaction formula. For instance,
    H2SO4 + 2 NaOH = 2NaSO4 + 2H2O.
     
  5. Sep 1, 2017 #4

    Borek

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    Staff: Mentor

    You are missing the point of the formula. Description is lousy, but the formula as given makes logical sense, especially taking into account fact the number used by OP (176.12) is a molar mass.

    Not exactly, there is also another factor that has to be taken into account, as the answer must be given per 100 mL.
     
  6. Sep 1, 2017 #5
    I am quite new to this all, do you have any links/keywords I could google to try follow stochiometery and dilution.

    I've got the reaction equation

    C6H8O6 +I2 -> 2I- + C6H6O6
     
  7. Sep 1, 2017 #6

    Borek

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    Staff: Mentor

  8. Sep 1, 2017 #7
    Thank you so much
     
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