Data
Calculations:
For the following table this equation is used to calculate the values in the second column, shown here with the example of the first row of data:
Sample calculation
= 0.0162 M vitamin C
Temp (oC): Time (m) Molarity of Vitamin C Solution
19.5 2 .0162
19.5 2 .0162
50 2 .0178
50 2 .0165
75 2 .0181
75 2 .0207
100 2 .0153
100 2 .0178
100 5 .0279
100 5 .0295
100 10 .0358
100 10 .0402
Percent Variance:
Experiment: % Variance
2 min @ 19.50C 0 = (.0162-.0162)/.0162
2 min @ 50oC 7.9 = (.0178-.0165)/.0165
2 min @ 75oC 14.4 = (.0207-.0181)/.0181
2 min @ 100oC 16.3 = (.0178-.0153)/.0153
5 min @ 100oC 5.7 = (.0295-.0279)/.0279
10 min @ 100oC 12.3 = (.0402-.0358)/.0358
Conclusion:
The length of exposure to a high temperature has a significant effect on the concentration of vitamin C. It is clear from the data that the longer the exposure to high temperatures, the greater the concentration. It appears that there is little effect on Vitamin C at temperatures below about 100 degrees Celsius. For the three lowest temperatures, all are very similar. There does appear to be a slight upward trend as the temperature increases, but this is small and is not conclusive, especially considering the relatively high % variance of the two trials when compared with the difference between concentrations. However when compared to the rest of the data, this contradicts the prevalent pattern. At 100 degrees, the data becomes more varied. There looks to be a slight to mild drop in concentration between the 75o test and the 100o test. However the percent of variances of these two samples are the two largest of all the experiment, and considering that his doesn’t seem to match the overall pattern of the results, it is possible this is merely an anomaly, though maybe not. The conclusion that the longer the exposure to heat, the higher the concentration of vitamin C is the complete opposite of my hypothesis. This does not make any sense, however. How could vitamin C be created by high temperatures, especially when ascorbic acid is supposed to be destroyed at this point? There has to be something wrong with the procedure.
The procedural method was very solid. It was fairly simple and straightforward, with pretty good precision. There were, however a couple possible sources of error. While we tried to add the extra ingredients consistently and according to the directions, using droppers is not very accurate and there being different quantities of these could affect the outcome. Also, it is difficult to find the exact point where the black becomes apparent, and is easy to add a little bit too much, undermining the accuracy of the results. However all these are fairly minor, and were carefully controlled whenever possible. So the method cannot be to blame for the unbelievable results, there must be a fundamental flaw in the titration procedure. The issue must be with the heated ascorbic acid because only the ascorbic acid and water and heated, and it’s inconceivable that hot water would significantly affect such a reaction. The differences cannot be caused merely by the hotter environment of titration, because all the trials at 100 degrees should cool at the same rate, yet have very different results. So there must be something about the heated vitamin C that causes it to react more with the free iodine. A possible explanation is that the altered state of the heated vitamin C causes it to oxidize with multiple iodine molecules. Another possible cause is that denatured vitamin C hinder the formation of free iodine in some way.
This experiment had major problems. The results were completely counterintuitive. Before this experiment could be done again, the source of this problem would have to be identified and remedied, or another method of measuring vitamin C would need to be found. Unfortunately, I’m not aware of a method for either and thus cannot suggest concrete changes to the experiment.
