Katy Salter
Real World Project: Iodimetric Titration of Vitamin C
Objective
The objective of this lab is to use iodometric titration method to determine the amount of
Vitamin C in orange juice that has been stored in different containers and stored at different
temperatures. Then test them a day after purchase and 2 weeks after purchase.
Procedure
1% Starch Indicator Solution
1.) Add 0.50 g soluble starch to 50mL near-boiling distilled water
2.) Mix well and allow cooling before use
Iodine Solution
1.) Dissolve 10.00 g potassium iodide (KI) and 0.536 g potassium iodate (KIO3) in 400 mL of
distilled water
2.) Add 60 mL of 3 M sulfuric acid
3.) Pour this solution into a 1 liter graduated cylinder and dilute it to a final volume of 1 liter
with distilled water
4.) Mix the solution
5.) Transfer the solution to a 1 liter reagent bottle
Vitamin C Standard Solution
1.) Dissolve 0.250 g vitamin C (ascorbic acid) in 100 mL distilled water
2.) Dilute to 250 mL with distilled water in a volumetric flask
Standardizing Solutions
1.) Add 25.00 mL of vitamin C standard solution to a 125 mL Erlenmeyer flask
2.) Add 10 drops of 1% starch solution
3.) Rinse your buret with a small volume of the iodine solution and then fill it
4.) Titrate the solution until the endpoint is reached (three trials)
5.) Record the final volume of iodine solution
Titrating Juice Samples
1.) Add 25.00 mL of orange juice sample to a 125 mL Erlenmeyer flask
2.) Add 10 drops of 1% starch indicator solution
3.) Titrate until the endpoint is reached
4.) Repeat the titration until you have at least three measurements that agree to within 0.1 mL
Data
Iodine added(mL)
Average volume added
Vitamin C(g)
Average grams of
Vitamin C
Vitamin C Standardization
Trial One
Trial Two
25.8mL
27.6mL
26.7mL
0.243g
0.260g
Trial Three
26.7mL
0.2515g
0.2515g
Vitamin C Concentration Titration
Tropicana No Pulp Non-Concentrate (25 mL in each sample)
Day After Purchase, Room Temperature, Opened
Trial One
Trial Two
6.32mL
6.2mL
Iodine added(mL)
6.27mL
Average volume added
0.00149
0.00146
Vitamin C(g)
Average grams of
0.00148
Vitamin C
Iodine added(mL)
Average volume added
Vitamin C(g)
Average grams of
Vitamin C
Iodine added(mL)
Average volume added
Vitamin C(g)
Average grams of
Vitamin C
Iodine added(mL)
Average volume added
Vitamin C(g)
Average grams of
Vitamin C
Day After Purchase, Fridge, Opened
Trial One
Trial Two
6.2mL
6.3mL
6.3mL
0.00146
0.00148
Trial Three
6.3mL
0.00148
Trial Three
6.4mL
0.00151
0.00148
Day After Purchase, Room Temperature, Sealed
Trial One
Trial Two
6.45mL
6.32mL
6.42mL
0.00152
0.00149
Trial Three
6.5mL
0.00153
0.00151
Day After Purchase, Fridge, Sealed
Trial One
Trial Two
6.35 mL
6.3mL
6.31mL
0.00150
0.00148
0.00149
Trial Three
6.28mL
0.00148
Two Weeks After Purchase, Room Temperature, Opened
Trial One
Trial Two
2.3mL
2.6mL
Iodine added(mL)
2.33mL
Average volume added
0.000542
0.000612
Vitamin C(g)
Average grams of
0.000549
Vitamin C
Iodine added(mL)
Average volume added
Vitamin C(g)
Average grams of
Vitamin C
Two Weeks After Purchase, Fridge, Opened
Trial One
Trial Two
5.4mL
5.0mL
5.17mL
0.00127
0.00118
0.000495
Trial Three
5.1mL
0.00120
0.00122
Two Weeks After Purchase, Room Temperature, Sealed
Trial One
Trial Two
5.2mL
5.6mL
Iodine added(mL)
5.43mL
Average volume added
0.00122
0.00132
Vitamin C(g)
Average grams of
0.00128
Vitamin C
Iodine added(mL)
Average volume added
Vitamin C(g)
Average grams of
Vitamin C
Trial Three
2.1mL
Two Weeks After Purchase, Fridge, Sealed
Trial One
Trial Two
5.7mL
6.2mL
5.93mL
0.00134
0.00146
0.00140
Calculated Theoretical Amount of Vitamin C in 25mL’s of Sample = 0.006338g
Trial Three
5.5mL
0.00130
Trial Three
5.9mL
0.00139
Calculations
Theoretical Amount of Vitamin C in Each 25mL’s of Sample
Actual Amount of Vitamin C per Sample:
Concentration of the standard = Concentration of the sample
g
Conclusion
In conclusion, the actual amount of vitamin C proved to be much less than what the
manufacturer claims. However this experiment was to test the amount of vitamin C under
different conditions. In this experiment the orange juice samples tested day one were more of the
controls in this case because we wouldn’t expect the vitamin C levels to degrade after being left
open or at room temperature for only a day. But after two weeks of either being left in the fridge
or left at room temperature and either being left opened or sealed, the most noticeable drop was
the sample of orange juice that was left for two weeks, at room temperature, and with the
container left open. With these results, this means that vitamin C will degrade over time if not
kept in an air tight container OR in the fridge. However not both of these conditions need to be
met because there wasn’t a very significant drop when the orange juice was sealed at room
temperature or left opened in the fridge. So it can be determined that both of those factors (airtight container and refrigerated) are helping to preserve the vitamin C.