Chem 14CL Summer 05The Titrimetric Analysis of Vitamin CNote: The Experimental Procedures for this Experiment are provided as a Handout, Which Will Handed out in Lab.Chem 14CL Summer 05This is an individual reportChem 14CL Summer 05 The Titrimetric Analysis of Vitamin C Note: The Experimental Procedures for this Experiment are provided as a Handout, Which Will Handed out in Lab. Pre-lab Guidelines: (I) Introduction: In this section outline the goal(s) of the experiment as well as the experimental techniques that you will be throughout the experiment. (II) Flowchart of the Procedures for the entire experiment and cite the reference for the Procedure. (III) MSDS information for L-ascorbic acid and sodium thiosulfate. Include the product name; the chemical formula, the formula weight; physical properties such as melting point, boiling point and density. (ITEMS I, II & III OF PRELAB IS DUE on 7/14 (IV) Pre lab study questions is due on 7/15 1. A 0.4283 g sample of KIO3 is transferred to a 250-mL volumetric flask, dissolved and diluted to the mark with distilled water. What is the molar concentration of the KIO3 solution? 2. A 25-mL aliquot of a 0.0104 M KIO3 solution is titrated to the stoichiometric point with 17.27 mL of a sodium thiosulfate, Na2S2O3, solution. What is the molar concentration of the Na2S2O3 solution? 3. Describe “how” the starch solution is used to detect the stoichiometric point in titration. 4. What is the color change at the stoichiometric point in vitamin C analysis? and what is the cause of the color change? 5. Explain why cooked fruits and vegetables have a lower vitamin C content than fresh fruits and vegetables. 6. In the vitamin C analysis, which is the oxidizing agent and which is the reducing agent? 7. Six ounces (1 fl. Oz. = 29.57 mL) of a well–known vegetable juice contains 35% of the recommended daily allowance of vitamin C (equal to 60 mg). How many milliliters of the vegetable juice will provide 100% of the recommended daily allowance? Chem 14CL Summer 05Post lab Report Guideline for Vitamin C Analysis This is an individual report (I) DATA AND OBSERVATIONS In your notebook, record the weights of each of your reagents, and any other qualitative observations that occurred during the solution preparation or titrations. (II) Calculations: (a) Part I (i) Calculate the moles of primary standard KIO3 and its molar concentration? (ii) Calculate the moles of I3- that are generated from KIO3? (iii) Calculate the molar concentration of Na2S2O3 for each titration and the average molar concentration of Na2S2O3 solution? (b) Part II (iv) Determine the number of moles of Na2S2O3 that you required for each of the titrations of vitamin C tablet. (v) Calculate the moles of I3- that are reacted with Na2S2O3 in the titrations for each trial? (vi) Calculate the moles of I3- that are reacted with vitamin C tablet in each trial? (vii) Determine the moles of vitamin C in each aliquot that you titrated. (viii) Based on the average value for your titrations, calculate the total moles of ascorbic acid, C6H8O6 in the “tablet.” (ix) Calculate the mass of ascorbic acid, C6H8O6 in the “tablet”? (III) Discussion: (i) Determine the percentage of ascorbic acid in the vitamin C tablet that you analyzed. (ii) Calculate the percent relative average deviation in your sodium thiosulfate titrations [Na2S2O3 ]and in your Vitamin C titrations (moles). (iii) Calculate the inherent error in the percentage of ascorbic acid you determined in the tablet. (iv) Does your error account for any “impurities” in the vitamin C tablet? If not, why not? (IV) Conclusion: Summarize your results Comment on %
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