lab report
Name: _____________________________
10
Exp 6. Report Form: Analysis of Vitamin C
Raw Data
Vitamin C Stock Solution Preparation:
Mass of Vitamin C (ascorbic acid) used to prepare stock solution _______________
(Total) Volume of Vitamin C stock solution (as prepared; not how much was transferred after!) _______________
Standardization Titrations:
Volume of Vitamin C (ascorbic acid) stock solution used for Titration 1 _______________
Initial iodine(aq) buret Reading, Titration 1 _______________
Final iodine(aq) buret Reading, Titration 1 _______________
Was this titration clearly (or likely) overshot? Y or N
Volume of Vitamin C (ascorbic acid) stock solution used for Titration 2 _______________
Initial iodine(aq) buret Reading, Titration 2 _______________
Final iodine(aq) buret Reading, Titration 2 _______________
Was this titration clearly (or likely) overshot? Y or N
Volume of Vitamin C (ascorbic acid) stock solution used for Titration 3 _______________
Initial iodine(aq) buret Reading, Titration 3 _______________
Final iodine(aq) buret Reading, Titration 3 _______________
Was this titration clearly (or likely) overshot? Y or N
Titrations of Beverage of Choice
Detailed description of beverage of choice: _________________________________________________________
Volume of sample of beverage (For Titration 1) _______________
Initial iodine(aq) buret Reading, Titration 1 _______________
Final iodine(aq) buret Reading, Titration 1 _______________
Was this titration clearly (or likely) overshot? Y or N
Volume of sample of beverage (For Titration 2) _______________
Initial iodine(aq) buret Reading, Titration 2 _______________
Final iodine(aq) buret Reading, Titration 2 _______________
Was this titration clearly (or likely) overshot? Y or N
Volume of sample of beverage (For Titration 3) _______________
Initial iodine(aq) buret Reading, Titration 3 _______________
Final iodine(aq) buret Reading, Titration 3 _______________
Was this titration clearly (or likely) overshot? Y or N
Report Form, Analysis of Vitamin C
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Calculated Quantities and Results, Standardization
# mg per mL of Vitamin C (ascorbic acid) in prepared stock solution: _______________
Titration 1 Titration 2 Titration 3
Mass of ascorbic acid used (mg) _______________ _______________ _______________
Moles of ascorbic acid used _______________ _______________ _______________
Moles I2 used _______________ _______________ _______________
Volume of I2(aq) (titrant) used (mL) _______________ _______________ _______________
Molarity of I2 in titrant solution _______________ _______________ _______________
Average molarity of I2 in titrant solution _______________
Calculated Quantities/Results, Beverage Samples
Titration 1 Titration 2 Titration 3
Volume of I2(aq) (titrant) used (mL) _______________ _______________ _______________
Moles I2 used _______________ _______________ _______________
Moles of ascorbic acid in sample _______________ _______________ _______________
Mass of ascorbic acid in sample (mg) _______________ _______________ _______________
Mass of ascorbic acid per mL of sample (mg/mL)_______________ _______________ _______________
Average Mass of ascorbic acid per mL of sample (mg/mL) _______________
Report Form, Analysis of Vitamin C
12
Analysis
1. What beverage(s) did you analyze? Write down here the serving size (in mL) and the amount of Vitamin C per
serving (in mg) from the label. [NOTE: If the amount of Vitamin C per serving is stated only as a percentage daily allowance (DA), contact your instructor for guidance (you may
need to look up on the web the current value of DA for Vitamin C in the USA)]
2. Using the average value that you determined for the number of mg of Vitamin C per mL of beverage (calculated
from your raw data), along with the volume of one serving size of your beverage (as noted in #1, from the label), calculate
the (experimental) mg of Vitamin C in one serving size of your beverage. How well does your experimental value
agree with the value found on the label? Comment on potential sources of error in the experiment.
3. Comment on the precision of your determinations of both (a) the molarity of the iodine solution (titrant) and (b) the
mg of Vitamin C per mL of beverage. State clearly what you are looking at to assess this.
4. (a) To better quantify the precision comparison noted in #3 above, assume that a rough approximation of the %
uncertainty in each of the determinations can be calculated as follows: First, calculate the range of values (for
both the molarity and the mg/mL quantities) and divide it by 2 (i.e., take the largest value you got in one of your
trials minus the smallest value and divide the result by 2). Then, take that result (for each quantity—molarity and
mg/mL), divide it by the average value of that quantity (calculated on the previous page), and multiply by 100.
Setups/Calcs for % Uncertainty of Molarity of I2 Setups/Calcs for % Uncertainty of mg/mL of Vitamin C in beverage
(b) Based on this measure, which determination was more precise, the molarity of the iodine solution or the mg of
Vitamin C per mL of beverage?