**Please see pages 114-119 in the lab manual provided for any extra information**

 

Goal: To measure the mass percent of vitamin C (ascorbic acid) in a mixture of solids. 

 

QUESTION: Using the experimental data below, calculate the weight percent vitamin C in the unknown. Report a relative standard deviation.

 

Standardization of Thiosulphate solution:

**Erlynmeyer flask filled with KIO3 solution during titration

Mass of KIO3 = 1.0854 g

Volume of KIO3 solution = 500 mL

Volume of KIO3 soultion per titration = 50 mL

Molar Mass of KIO3 = 214 g/mol

**Burette filled with sodium thiosulphate

Initial burette reading / mL: trial 1 - 0.17mL trial 2 - 0.12mL trial 3 - 0.14mL

Final burette reading / mL: trial 1 - 39.48mL trial 2 - 39.48mL trial 3 - 39.46mL

 

(1) IO₃^- (aq) + 8 I^- (aq) + 6 H⁺ (aq) à 3 I₃^- (aq) + 3 H₂O (l)

(2) I₃^- (aq) + 2 S₂O₃^2- A(aq) --> 3 I^- (aq) + S₄O₆^2- (aq)

 

Determination of Vit. C Content:

Mass of Vit. C sample = 1.1186 g

Volume of Vit. C solution = 250 mL

Aliquot volume of Vit. C solution = 25 mL

**Burette filled with Sodium Thiosulphate

Initial burette readings: trial 1 - 0.08 mL trial 2 - 0.14 mL trial 3 - 0.06 mL

Final burette readings: trial 1 - 33.22 mL trial 2 - 33.26mL trial 3 - 33.22mL

Molar Mass of Vit. C = 176.13

 

(3) C₆H₈O₆ + I₃^- + H₂O --> C₆H₈O₆ + 3 I^- + 2 H⁺

 

 

The correct result for the question is:

Average mass Vitamin C per g of mixture = 0.3771 g

% RSD = 0.3

 

Please explain each step that you are doing so that i can understand where your numbers and calculations are coming from! THANKS!

Also, if you need any more information I will be happy to provide it!

• 1503036535-Chem 2030 lab manual S17.pdf

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