Using the experimental data below, calculate the weight percent of Vitamin C in
ID: 908637 • Letter: U
Question
Using the experimental data below, calculate the weight percent of Vitamin C in the unknown. Report a relative standard deviation.
Standardization of Thiosulphate Solution Mass KIO3 mass of KIO3 + weighing vial / g 24.5882 1.0926 mass of weighing vial / g 23.4956 V KIO3 / mL 500.0 V KIO3 per titration / mL 50.00 trial 1 2 3 Initial burette reading / mL 0.12 0.08 0.10 Final burette reading / mL 39.16 39.10 39.16 Amount Used 39.04 39.02 39.06 Determination of Vitamin C Content mass of sample / g 2.6158 Volume of Vitamin C solution / mL 250.00 Aliquot Volume of Vitamin C solution / mL 25.00 trial 1 2 3 Initial burette reading / mL 0.06 0.14 0.10 Final burette reading / mL 26.22 26.34 26.28 amount used 26.16 26.20 26.18 Molar Mass Vitamin C 176.13 Correct Result Average mass Vitamin C per g of sample / g 0.340 %RSD 0.2Explanation / Answer
Molarity of KIO3 solution = moles/L = g/molar mass x L = 1.0926/214 x 0.5 = 0.0102 M
mass of ascorbic acid sample = 2.6158 g
1 mole of KIO3 reacts with 3 mols of ascorbic acid
moles of KIO3 used = 0.0102 M x 26.16 = 0.267 mmols [trial 1]
moles of KIO3 used = 0.0102 x 26.20 = 0.267 mmols [trial 2]
moles of KIO3 used = 0.0102 x 26.18 = 0.267 mmols [trial 3]
average = 0.267 mmols
moles of ascorbic acid = 0.267 x 3 = 0.801 mmols
mass of ascorbic acid = 0.801 x 176.13 = 0.1411 g in 2.6158 g sample
per gram of sample = 0.054 g = 5.4% wt%
%RSD = 0.0002
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