1. Nisarg J. Vyas Experiment 6 Student ID: 100567707
Experiment: 6 Ascorbic
Acid in Vitamin C Tablets
Name: Nisarg J. Vyas
Student ID: 100567707
Lab Partner: Nick Campbell
Lab Performed: 19 February 2015
Lab report due: 05 February 2015
Lab Instructor: Jennifer A. Smith
Course Code: CHEM-2131

2. Nisarg J. Vyas Experiment 6 Student ID: 100567707
Table of Contents
Objective:...................................................................................................................................... 1
Method: ......................................................................................................................................... 1
Equipment:................................................................................................................................. 2
Chemical Reaction: ................................................................................................................. 2
Observations: ................................................................................................................................ 3
Calculations:.............................................................................................................................. 3
Discussion:...................................................................................................................................... 5
Conclusion:.................................................................................................................................... 6
Post Lab Questions: ...................................................................................................................... 7
Figure 1 Reaction between ascorbic acid and iodine solution ............................................ 2
Figure 2 Chart of obtained results.............................................................................................. 5
Table 1 Table of Reagents and Safety information................................................................. 1
Table 2 Table of Equipment ........................................................................................................ 2
Table 3 Table of Observations .................................................................................................... 3
Table 4 Table of Final Calculations. ........................................................................................... 4

3. Nisarg J. Vyas Experiment 6 Student ID: 100567707
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Experiment 6: Ascorbic acid in Vitamin C Tablets.
Objective:
Amount of ascorbic acid will be determined in vitamin C tablets by performing
redox titration with Iodine solution to 3 samples of vitamin C tablets dissolved in
carbon dioxide free with sulfuric acid and starch as indicator. Amount of titrated
iodine will be recorded and used to calculate the amount of ascorbic acid
present in each tablet.
Method:
Table 1 Table of Reagents and Safety information
NO. CHEMICAL NAME FORMULA SAFETY INFORMATION LOT NO.
1 Sulfuric Acid H2SO4 Corrosive N/A
2 Iodine Solution I2 Corrosive 60314
3 Starch C6H10O5 Combustible N/A
4 Vitamin C/Ascorbic Acid C6H8O6 Irritant 3533904

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Equipment:
Table 2 Table of Equipment
NUMBER EQUIPMENT
1. 25 ml pipette
2. Burette
3. 3 250 ml Erlenmeyer flask
4. 10 ml graduated cylinder
Please follow the lab manual, pg. no 43 for detailed step by step method.
Chemical Reaction:
Figure 1 Reaction between ascorbic acid and iodine solution

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Observations:
Weight of 10 tablets: 14.0403 g
Table 3 Table of Observations
SAMPLE NUMBER MASS OF EACH SAMPLE AMOUNT OF IODINE
TITRATED
COLOUR
CHANGE
1 0.4030 g 17.10 ml Colourless to
Dark purple
2 0.4007 g 16.02 ml Colourless to
Light purple
3 0.4058 g 16.40 ml Colourless to
Light purple
Calculations:
Weight of the 10 tablets: 14.0403 g
Average weight of the 01 tablet:
=
𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑎𝑙𝑙 𝑡𝑎𝑏𝑙𝑒𝑡𝑠
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑎𝑏𝑙𝑒𝑡𝑠
=
14.0403 𝑔
10
= 1.404 𝑔
Since each ml of iodine is equivalent to 8.806 mg of ascorbic acid:
1 ml iodine = 8.806 mg Ascorbic acid
To calculate mg of ascorbic acid in each sample:
For sample 1:
17.10 𝑚𝑙 × 8.806
𝑚𝑔
𝑚𝑙
= 150.58 𝑚𝑔
∴ 150.58 𝑚𝑔 𝑜𝑓 𝐴𝑠𝑐𝑜𝑟𝑏𝑖𝑐 𝐴𝑐𝑖𝑑 𝑖𝑠 𝑝𝑟𝑒𝑠𝑎𝑛𝑡 𝑖𝑛 𝑠𝑎𝑚𝑝𝑙𝑒 1.

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Using the Same calculations Ascorbic Acid present in each sample can be
found.
To calculate ascorbic acid in each tablet,
150.58 𝑚𝑔
0.4030 𝑔
=
𝑥
1.404 𝑔
𝑥 = 524.60 𝑚𝑔 ≈ 525 𝑚𝑔
To calculate percentage of ascorbic acid in each tablet,
525
500
× 100% = 105%
Table 4 Table of Final Calculations.
SAMPLE
NUMBER
SAMPLE WEIGHT A.ACID IN SAMPLE A.ACID IN
TABLET
% FOUND
SAMPLE 1 0.4030 g 150.58 mg 525 mg 105%
SAMPLE 2 0.4007 g 141.07 mg 494 mg 98.8%
SAMPLE 3 0.4058 g 144.41 mg 500 mg 100%
Average weight of all 3 sample:
=
525 𝑚𝑔 + 494 𝑚𝑔 + 500 𝑚𝑔
3
= 506 𝑚𝑔
Percentage Calculated:
=
506
500
× 100%
= 101.2%
506 mg, 101. 2 % present in each tablet.

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Discussion:
When performing a titration, end point of the reaction was reached when the
colour of the solution changed from colourless to light purple. This occurred
because as the iodine is added during the titration, the ascorbic acid is oxidised
to dehydroascorbic acid, while the iodine is reduced to iodide ions. Due to this
reaction, the iodine formed is immediately reduced to iodide as long as there is
any ascorbic acid present. Once all the ascorbic acid has been oxidised, the
excess iodine is free to react with the starch indicator, forming the light purple
starch-iodine complex. When the chart below is analyzed,
Figure 2 Chart of obtained results.
It is clearly seen that weight of sample affects the amount of ascorbic acid
present in each tablet. As the weight of the sample increase, so does the weight
494
525
500
490
495
500
505
510
515
520
525
530
0.4 0.401 0.402 0.403 0.404 0.405 0.406 0.407
Weightoffoundproductineachtablet
(mg)
Weight of Each Sample (g)
Weight of sample Vs. Weight of Vitamin C in each
tablet

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of the present ascorbic acid in each sample. However there was an error while
titrating sample 1, when the amount of Vitamin C present in the tablet is
calculated it comes up to 525 mg, which is higher than sample 2 and 3. It is clearly
visible in the chart. The reason behind this error is that too much of titrant was
added, resulting in the dark purple than light purple. To avoid this kind of error,
one must perform the titration with much care and precision. In the end when the
average calculated it was similar to expected value, which was 506.2 mg, 101.2%
According to USP guidelines amount of ascorbic acid in each tablet should be
between 90-110%, which was achieved in this lab.
Conclusion:
In conclusion, amount of ascorbic acid present in Vitamin C tablet by performing
a redox titration with accuracy and precision, which was achieved during this lab.

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Post Lab Questions:
1. Describe the procedure that must be used to make 100 ml of 0.0001M H2SO4
from a 12M H2SO4 stock solution. This is a serial dilution problem. Include all
calculations.
A. Molar mass of H2SO4 = 98.079 g/ mole
Using the following Equation:
𝐶1 𝑉1 = 𝐶2 𝑉2
𝑉1 =
𝐶2 𝑉2
𝐶1
C1 = 12 M
C2 = 0.0001 M
V1 =?
V2 = 100 ml
𝑉1 =
(0.0001 𝑀)(100 𝑚𝑙)
12 𝑀
=
0.01
12
= 8.3333 × 10−04
𝑚𝑙
V = V2- V1 = 99.99 ml
Place 8.3333 × 10−04
𝑚𝑙 of 12M H2SO4 in to 99.99 ml of diluent.