Circle the questions that have been assigned. 1. Part A.1. The K1O, sample was n
ID: 1046777 • Letter: C
Question
Circle the questions that have been assigned. 1. Part A.1. The K1O, sample was not sufficiently dried. Will the reported molar concentration of the KIO, solution (Part B.3) be too high, too low, or unaffected? Explain. Part A.?. The mass of KIO, used to prepare the solution was measured to be 0.585 g instead of the calculated 0.535 g. a. Will the molar concentration of the KIO, solution be greater or less than 0.01 M KIO,? Explain. b. As a result of this (now) prepared KIO, solution, will more or less volume of KIO, solution be used for the vitamin C analysis? Explain. Part B.1. The NaHCO, solution is omitted in an analysis of the sample. Will the reported amount of ascorbic acid in the sample be too high, too low, or unaffected? Explain. 4, Part C.I. Explain why the mass of KI (-1 g), and the volume of starch (-2 mL) are only approximate even though the analysis is quantitative. 5. Part C.2. After adding the standard solution of KIO, to the prepared analyte, the sample solution never forms the deep- blue color. What modification of the Experimental Procedure or error corrected can be made in order to complete the analysis? Part C.2·The deep blue color of the 1, starch complex does not appear but a yellow-brown does appear! What next? Should you continue titrating with the standard KIO, solution or discard the sample? Explain. 6 7 Part C.2. The final buret reading is read and recorded as 27.43 mL, instead of the correct 28.43 mL. Will the reported amount of ascorbic acid in the sample be too high or too low? Explain. 348 Vitamin C AnalysisExplanation / Answer
2.
Mass of KIO3 taken = 0.585g
molecular mass of KIO3 = 214.01g/mol
mole of KIO3 = 0.585/214.01= 0.0027mol
this solution concentration is 0.002M if the solution dissolved in 1litre solvent.
according to question
the Molar concentration of the solution is less than the 0.01M KIO3. because prepared solution concentration is 0.002M KIO3.
(b).
since the concentration of the prepared KIO3 solution is less than so more volume of KIO3 is required to neutralise the titration.
3. The sodium bicarbonate (a base) is reacting with the ascorbic acid to form sodium ascorbate and carbon dioxide, as well as water. When you mix the two solids, the reaction is relatively slow, since the reaction must take place at the interface of the two solids; however, it appears that allowing it to sit overnight is sample time. The hardening is probably due to the release of water, which causes to solid to aggregate; the solid will no longer bubble in water as it has already reacted and released its carbon dioxide. due to above region sodium bicarbonate is omitted in an analysis of the sample.
you didn't mention about the amount of ascorbic acid taken so it is difficult to tell sample is small or high.
4.
In the iodometric titration of ascorbic acid - you are titrating the acid against a standard I2 solution. The starch and KI are used as the indicator for the endpoint - when the iodine titrant has reacted with all the ascorbic acid. Because the starch and KI do not enter into the quantitative reaction - but act only as an indicator system - the exact quantity is not important.
5.
The pipette out the sample solution into a conical flask and add about potassium iodide, starch indicator solution.
then titrate the sample with the 0.002 mol L?1 potassium iodate solution. The endpoint of the titration is the first permanent trace of a dark blue-black colour due to the starch-iodine complex. if the sample solution does not convert to the deep blue colour then we can add some more KI and starch indicator solution.
6.
instead of deep blue colour if the yellow-brown colour appears then we should continue the titration with shacking continuously.