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?
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
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.
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.
To calculate the weight percent of ascorbic acid in the tablet of Vitamin C, you'll need to follow a series of steps:
Step 1: Determine the moles of thiosulfate used in the titration.
- Calculate the moles of thiosulfate used by multiplying the volume of the thiosulfate solution (in L) by its molarity (in mol/L).
Step 2: Find the moles of iodine liberated in the reaction.
- The thiosulfate solution reacts with the iodine (I2) produced from the reaction between KI and KIO3. The balanced equation is: 2S2O3^2- + I2 -> S4O6^2- + 2I^-
- From the balanced equation, you can see that 2 moles of thiosulfate react with 1 mole of iodine.
- Therefore, the moles of iodine liberated can be obtained by dividing the moles of thiosulfate used by 2.
Step 3: Calculate the moles of KIO3 used.
- The balanced equation for the reaction between KI and KIO3 is: 5KI + KIO3 + 3H2SO4 -> 3I2 + 3K2SO4 + 3H2O
- From the balanced equation, you can see that 1 mole of KIO3 is used for every 5 moles of KI.
- Find the moles of KIO3 used by dividing the moles of iodine liberated by 3.
Step 4: Determine the moles of ascorbic acid.
- The balanced reaction between ascorbic acid and iodine is: C6H8O6 + I2 -> C6H6O6 + 2HI
- From the balanced equation, you can see that 1 mole of ascorbic acid reacts with 1 mole of iodine.
- Therefore, the moles of ascorbic acid can be calculated by equating it to the moles of iodine liberated.
Step 5: Calculate the weight of ascorbic acid in the tablet.
- Multiply the moles of ascorbic acid by its molar mass, which is 176.12 g/mol.
Step 6: Calculate the weight percent.
- Divide the weight of ascorbic acid in the tablet by the weight of the tablet and multiply by 100 to obtain the weight percent.
By performing these steps with the given data, you will be able to calculate the weight percent of ascorbic acid in the tablet of Vitamin C.