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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Tahseen on August 08, 2017, 07:42:14 AM

Title: Redox titration of vitamin c and iodine
Post by: Tahseen on August 08, 2017, 07:42:14 AM
So my goal is to find how many mg/100ml of vitamin c (ascorbic acid) is in a bottle of orange juice depending on how much iodine was used to reach the end point.
The chemical equation is:

C6H8O6 + I2 :arrow: 2I- + C6H6O6 + 2H+

What is known is that the concentration of I2 is 0.01mol/L and that the Iodine needed to react with all the ascorbic acid is 0.003593L. By using c=n/v the moles given would be 0.00003593 or 3.593x10-5.
Due to the ratio of vitamin c and the iodine being the same, therefore it can be said that the moles of vitamin c is also the same, 3.593x10-5.

Now what I need help with is that I am having trouble trying to find the concentration of the vitamin c.
I originally got 20ml of pure orange juice out of a 2L orange juice bottle and mixed it with 80ml of distilled water. I then used 20ml of that solution to titrate to find that iodine amount. I dont know how to find the dilution factor and dilution using the formula c1v1=c2v2

edit: the M.M of ascorbic acid is 176.12g/mol.

Thanks!
Title: Re: Redox titration of vitamin c and iodine
Post by: Borek on August 08, 2017, 10:18:27 AM
Trace the number of moles, calculating dilutions is just a mass conservation at work.

You know number of moles in 20 mL of the final solution. What part of the initial solution is it?
Title: Re: Redox titration of vitamin c and iodine
Post by: Tahseen on August 09, 2017, 04:37:33 AM
How am I supposed to know. I asked the question of this. But I found out how to do it so its all goods.
Title: Re: Redox titration of vitamin c and iodine
Post by: sjb on August 09, 2017, 09:58:49 AM
Quote from: Tahseen on August 09, 2017, 04:37:33 AM
How am I supposed to know. I asked the question of this. But I found out how to do it so its all goods.

Great - why not share to help others who may pass this way in the future?
Title: Re: Redox titration of vitamin c and iodine
Post by: Vidya on August 11, 2017, 01:14:25 AM
Ok  ...You know moles of Ascorbic acid in 20 mL of the sample titrated finally ...
Calculate the molarity of the solution.This will be the molarity of solution which you have made by adding 80 mL of water.
Now use dilution eq
C1V1=C2V2
V1= 20 mL (Juice from the bottle )
C1 is concentration of Vit C in the juice bottle.
C2 is the concentration of diluted solution which you determined from titration.
V2 is the volume of diluted solution(100mL)