Assignment - Part 1 - Underlying Chemistry

Question 1

Title and Aim ?

Answer 1

Title: Mass of vitamin C in tablets

Aim: To determine the mass of Vitamin C in three different Vitamin tablets.

Question 2

para 1 ?

Answer 2

Vitamin C/ ascorbic acid

Reacts with iodine in redox, water soluble

Calculate mass of Vit C in tablet by redox titration with stock vit C solution + iodine solution + starch indicator.

Chemical equation of vit C and iodine: C6H806 (aq) and I2

Vit C and iodine react in redox to form dehydroascorbic acid, iodide ions and hydrogen ions:

C6H806 (aq) + I2 (aq) —> C6H606 (aq) + 2I-(aq) + 2H+(aq)

Question 3

para 2 ?

Answer 3

What is redox ?

Question 4

para 3 ?

Answer 4

Reduction and Oxidation steps of redox reaction between Vit C and Iodine are

Oxidation:

C6H806 (aq) —> C6H606 (aq) + 2e- + 2H+(aq)

Reduction:

I2 (aq) + 2e- —> 2I-(aq)

Question 5

para 4 ?

Answer 5

Explain from ion-electron what is being reduced/oxidised, how do we know this from the equations.

Question 6

para 5 ?

Answer 6

Explain what is acting as the reducing/oxidizing agent.

Question 7

para 6?

Answer 7

-A titration is a technique that allows for the calculation of an unknown concentration, through volumetric analysis. A volumetric analysis involves using a solution of accurately known concentration (in this case, the iodine solution) to determine the concentration of another substance (in this case, the vitamin C solution).

-From knowing the concentration of the vitamin C solution, and using the volume of vitamin c solution, we can calculate the mass of vitamin C present in a tablet.

-This titration is an example of a redox titration. A redox titration is the titration of an oxidising agent against a reducing agent.

-At the redox titration’s equivalence point, precisely enough electrons have been removed to oxidise all of the reducing agent.

-By using a starch indicator, we can see when iodine is in excess, as all the vitamin C will have reacted with iodine. The excess iodine will react with the starch indicator to produce a visible colour change, allowing the determination of the end point of the reaction.

-Knowing when the end point occurs allows us to know what volume of iodine is needed to react with all of the vitamin C – knowing this volume is also needed to calculate the mass of vitamin C present in our sample of solution.

-This is the method by which I will calculate the mass of vitamin C present in these tablets.