In Procedure B, Step 2, why wasn’t it necessary to record the exact volume of wa

Question

In Procedure B, Step 2, why wasn’t it necessary to record the exact volume of water added to the flask?

Part B. Preparation of Vitamin C Tablet Solutions

1. Obtain three vitamin C tablets. Place a plastic weighing boat on the balance, and press zero to tare the balance. Place the pieces in the tared weighing boat, and record the exact mass of the tablet in your LAB NOTEBOOK. MAKE SURE TO RECORD ALL OF THE DIGITS! Repeat this procedure for the second and third tablet in a separate plastic weighing boat.

2. Crush each tablet by placing it between two plastic weighing boats and applying firm pressure with a pestle, as demonstrated by your instructor. Transfer the tablets to separate, labeled 250 mL Erlenmeyer flasks. Add 40-50 mL of deionized water to each sample. Use a hotplate at your lab bench to heat the flasks (heat setting between 3-4, or 80ºC).   Heat gently for about ten minutes to dissolve the vitamin C tablets. The binder in the tablet will not completely dissolve, leaving some residue. Set these solutions to the side to cool to room temperature while you condition your buret for the titration in part C

Explanation / Answer

In step 2, Water is required to separate vitamin C from vitamin C tablets. For this purpose first tablets are changed in to powder and then dissolved in Water by heating so that all vitamin C goes in Water and binder remain undissolved and are separated by filteration. There may be water loss by heating also.Therefore an approximate quantity is required.

However before doing the titration in next step, Water solution containing dissolved vitamin C should be fixed to particular volume by addition of more deionized Water to calculate exact concentration of vitamin C by titration.

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