Question

Could someone show me step by step how to solve this type of problem? I have to do several of them, and would love to understand what is actually happening! Thank you so much in advance, I appreciate your help and time!

Calculate the weight percent of ascorbic acid in a tablet of Vitamin C from the following data:
A 70 mg sample of a crushed Vitamin C tablet was dissolved in 40 mL of H2SO4 and 20 mL of water. Two grams of KI and 25 mL of 0.00932 M KIO3 solution was added, and the mixture titrated to a starch endpoint. The titration required 12 mL of 0.0610 M thiosulfate solution.
What is the weight percent?

Answer 1

Just use their combined volumes as the dilution volume of the sample. 90 mg sample dissolved in a total of 60 mL.

Answer 2

Here is a very detailed document. Read through that and see if it helps. I've not seen one this detailed in some time. All of the reactions are there although it is a little light on the stoichiometry part.
http://www.lasalle.edu/~prushan/Experiment8-redox%20titration.pdf

Answer 3

I'm really sorry, but I still don't understand how all the amounts relate to each other, and I am about at my wits end. I'm not very good at math, but I am normally pretty good at chemistry and problem solving, and I don't know why I still don't get this. If you don't have time for step by step, can you tell me what the amounts mean and how they relate to each other? I would have taken this to my TA or professor, but both have been unavailable for days.

Answer 4

A vitamin C (C6H8O6) tablet was crushed and dissolved in water. Potassium iodide, hydrochloric acid and starch were added. The solution was titrated with 0.0100 mol dm-3 potassium iodate solution, 17.60 cm3 being required. Calculate:
(a) the amount of iodate used.
(b) the amount of vitamin C in the tablet
(c) the mass of vitamin C in the tablet.