lab3report - 29.80 29.90 31.30 Total Volume of S 2 O 3 2(mL...

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Carla Paulo Exercise 3 Analysis of Vitamin C Purpose: To determine the percentage of ascorbic acid in an unknown by oxidizing it with iodine. Unknown #: Unknown 3I Important Equations: C 6 H 8 0 6 (Ascorbic Acid)+ I 2 C 6 H 6 O 6 + 2H + + 2I - IO 3 - + 5I - + 6H + 3H 2 O + 3I 2 I 2 + 2S 2 O 3 2- 2I - + S 4 O 6 2- Safety Factors: Wear goggles and gloves throughout the experiment. Read labels carefully because chemicals used have similar names. Raw Data: A. Preparation of Standard KIO 3 Mass Vial Initial (g) 30.0238 Mass Vial Final (g) 28.3607 Mass of KIO 3 (g) 1.6631 B. Titration of Standard Trial 1 Trial 2 Trial 3 Trial 4 Volume of Na 2 S 2 O 3 Initial (mL) 0.40 0.35 0.20 1.10 Volume of Na 2 S 2 O 3 Final (mL) 43.20 43.15 42.95 43.90 Total Volume of Na 2 S 2 O 3 (mL) 42.80 42.80 42.75 42.80 C. Preparation of Unknown Trial 1 Trial 2 Trial 3 Trial 4 Mass of Vial Initial (g) 25.7838 25.4736 25.1691 24.1622 Mass of Vial Final (g) 25.4736 25.1691 24.8292 23.8685 Mass of Unknown (g) 0.3102 0.3045 0.3399 0.2937 D. Titration of Unknown
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Trial 1 Trial 2 Trial 3 Trial 4 Volume of S 2 O 3 2- Initial (mL) 0.30 0.35 0.80 0.60 Volume of S 2 O 3 2- Final (mL) 33.10
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Unformatted text preview: 29.80 29.90 31.30 Total Volume of S 2 O 3 2-(mL) 32.80 29.45 29.10 30.70 E. Treatment of Results 1. Molarity of KIO 3 1.6631g KIO 3 x (1 mol KIO 3 / 214g KIO 3 ) x (1/0.500L)= 0.0155M 2. Molarity of Na 2 S 2 O 3 Trial 1 0.0155M KIO 3 x 0.050L = 7.75x10-4 mol KIO 3 7.75x10-4 mol KIO 3 x (3mol I 2 /1mol KIO 3 )x (2mol S 2 O 3 2-/1mol I 2 )x (1/0.04280L)= 0.109M S 2 O 3 2 Trial Molarity 1 0.109M 2 0.109M 3 0.109M 4 0.109M Average Molarity: 0.109M 3. Mass of Ascorbic Acid in Unknown Trial 1 0.03280L S 2 O 3 2-x(0.109mol S 2 O 3 2-/1L)x(1mol I 2 /2mol S 2 O 3 2-)x(1mol C 6 H 8 O 6 /1mol I 2 )x(176.12g/ 1mol C 6 H 8 O 6 )= 0.3148g C 6 H 8 O 6 % Ascorbic Acid in the Unknown: (0.3148g C 6 H 8 O 6 /0.3102g) x 100= 101.5% Trial Mass C 6 H 8 O 6 % in unknown 1 0.3148g 101.5% 2 0.2827g 92.84% 3 0.2793g 82.17% 4 0.2947g 100.3% Average percentage in unknown: 94.20% Standard deviation: 8.89...
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This note was uploaded on 12/07/2011 for the course CHEM 328 taught by Professor Soriaga during the Spring '10 term at Texas A&M.

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lab3report - 29.80 29.90 31.30 Total Volume of S 2 O 3 2(mL...

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