Vitamin C tablet preparation. Record the mass of the entire tablet. Crush vitami
ID: 1045571 • Letter: V
Question
Vitamin C tablet preparation.
Record the mass of the entire tablet.
Crush vitamin C tablet in a mortar and pestle.
Weigh out ~100 mg of the tablet.
Dissolve the tablet sample in ~40 mL of 0.5 M sulfuric acid. Add 0.5 g sodium carbonate.
Add 25.00 mL of the primary standard iodate solution.
Add 1 g KI, 15 mL 0.5M sulfuric acid and 0.1g sodium carbonate
Immediately titrate with thiosulfate solution as above.
Repeat with a second 100-mg sample of the previously massed/crushed tablet.
Calculate the mass of vitamin C that was present in the portion of the tablet of your first titration. Show ALL calculations.
Trial 1
Initial Mass Thiosulfate
50mL
Mass of Vitamin C Tablet
0.65713g
Mass of Vitamin C
0.101g
Volume of Titrant 1st Endpoint
24.5mL
Volume of Titrant 2nd Endpoint
26mL
Trial 1
Initial Mass Thiosulfate
50mL
Mass of Vitamin C Tablet
0.65713g
Mass of Vitamin C
0.101g
Volume of Titrant 1st Endpoint
24.5mL
Volume of Titrant 2nd Endpoint
26mL
Explanation / Answer
Let's see what happens chemically during the titrimetric estimation of Vit-C.
First, iodate reacts with I- to generate triiodate (I3-).
Second, I3- reacts with ascorbic acid (Vit-C) to generate dehydroascorbic acid.
Third, Remaining I3- reacts with thiosulfate during final titration with thiosulfate in burette.
Therefore, If we can calculate how much I3- was originally present before reacting with ascorbic acid and How much I3- got titrated with thiosulfate, then the difference between these two values correspond to the amount of ascorbic acid.
The data provided here, does not allow me to calculate the initial concentration of I3- as the iodate concentration is not known.
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