Question

Suggest how the experiment (determination of vitamin C) could be modified to reduce the size of the standard deviation. (4 marks)

Answer 1

The determination of Vitamin C (ascorbic acid) is performed through Iodometric titration using a whole fruit ( lemon or orange). By the means of titration, the iodine concentration can be found out. In the iodine concentration case, a difference in standard deviations is observed when the buret size is varied. There will be no difference in precision nor accuracy in the F and T tests if the samer sized burets are used. When the large and small burets are compared there is a difference in the precision and accuracy for both the iodine concentration and the ascorbic acid obtained per amount of the whole fruit taken for the experiment. In the case of large burets lower value of iodine concentration and the ascorbic acid content is obtained when compared to that of small burets and thus slightly smaller value of deviation is obtained. Normally it is assumed that small burets have high accuracy and precision because of their small diameter but using larger burets gives the expected precision and thus an error is produced in the deviations from the truth when subjected to F and T tests.