These pictures are drawn to help you think of the same flask at three different

Question

These pictures are drawn to help you think of the same flask at three different points in time: immediately after the K3O_2 is added, after the vitamin c pill has been added and dissolved, after the titration has been completed. This hopefully mimics the work that you carried out in the second part of the lab. Mix KIO_3 with excess KI and H_2SO_4 to generate brown colored I^-_3 according to the reaction shown above. Dissolve a vitamin C tablet This releases C_6H_3O_6 molecules that remove some of the yellow colored I^-_3 via the reaction shown above. The lab is set up so that I^-_3 is present in excess. Thus, after all of molecules have reacted some yellow I^-_3 will be left behind. If 7 KIO_3 molecules were added to the flask at the start of the experiment. How many molecules of brown I_3- would have been generated? How many S_2O_3^2- ions were delivered to reach the titration endpoint? How many I_3- ions (left over after the vitamin C finished reacting) were removed by titration with S_2O_3^2- solution? How many I_3- ions must have been removed by non with vitamin c? How many molecules of vitamin C must have been present in the tablet? I^-_3 + 2S_2O_3^2- rightarrow 3I^- + S_4O_6^2- Add as many of S_2O_3^2- as needed to fully remove the remaining I^-_3 (add until clear endpoint) according to the titration reaction shown above.

Explanation / Answer

(1)

From the reaction stoichiometry,

1 molecule IO3- produces 3 molecules of I3-

So, molecules of I3- produced from 7 molescules KIO3 ( = 7 molecules IO3-) = 3*7 = 21 molecules

(2)

For this part you need to give the molarity as well as volume of the aqueous S2O32- solution ( mostly Na2S2O3 slution) added.

Number of S2O32- ions needed to reach the end point = Molarity*Volume in liters*2

Let's call this calculated number as 'x'

(3)

Ions of I3- removed through the titration reaction = x/2

(4)

Ions of I3- removed thorugh reaction with vit. C = Initial numbers of ions - (x/2)

Let's call this number 'y'

(5)

Molecules of Vit. C that must have been present = y

Put the required data values in above variable to calculate the final answers.

Revert back if you have any queries.

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