Question

An alternative titration method for determining the concentration of vitamin C in a sample is to...

An alternative titration method for determining the concentration of vitamin C in a sample is to use an iodine solution. In this reaction iodine oxidizes the ascorbic acid to C6H6O6.

A 20.00 mL sample of a 1.00 mg/mL vitamin C solution is placed in a flask along with 1 mL of a 1% starch solution to serve as an indicator. A dilute solution of iodine is placed in a buret. A titration is performed using the intense blue color produced by the reaction of excess I2 with the starch as an indicator that the endpoint has been achieved. The titration was repeated using a 20.00-mL sample of juice. The following data were obtained in this experiment.

Initial Buret Reading

Final Buret Reading

Standard Vitamin C sample

3.23 mL

8.54 mL

Juice Sample

8.54 mL

11.39 mL

a. Write the two balanced half reactions for this titration and the balanced net ionic equation.

b. What was the concentration (molarity) of iodine in the titrant?

c.   What was the concentration (mg/mL) of Vitamin C in the juice sample?

Homework Answers

Answer #1

ascorbic acid + I2 → 2 I− + dehydroascorbic acid

since meq of ascorbic acid = meq of I2

hence concentraion of vitaminc C in the standard sample = 20 mg in in 20 ml

hence conc inmolarity = (20 X 10-3 / 176.12 ) 1000 / 20

= 5.68 X10-3 M

hence

20 X 5.68 X10-3 = (8.54-3.23) X C I2

C I2 = 0.0214 M

hence now we can calculate teh concentraionof the vitaminc C in juice sample =

as 20 X C vitamin C = 0.0214 X (11.39-8.54)

C vitamin C =3.05 X 10-3 M

or conc in g per ml = 3.05 X 10-3 X 176.12 = 0.537 mg in 20 ml

Know the answer?
Your Answer:

Post as a guest

Your Name:

What's your source?

Earn Coins

Coins can be redeemed for fabulous gifts.

Not the answer you're looking for?
Ask your own homework help question
Similar Questions
If a 108.3 ml sample of grapefruit juice takes 10.14 ml of a 0.01720 M standarized...
If a 108.3 ml sample of grapefruit juice takes 10.14 ml of a 0.01720 M standarized iodine solution to reach the starch end point, what is the concentration of Vitamin C in units of mg/ml?
Calculate the weight percent of ascorbic acid in a tablet of Vitamin C from the following...
Calculate the weight percent of ascorbic acid in a tablet of Vitamin C from the following data: A 100 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 20. mL of 0.0138 M KIO3 solution was added, and the mixture titrated to a starch endpoint. The titration required 9.0 mL of 0.0750 M thiosulfate solution. Weight =
Vitamin C tablets contain ascorbic acid (C6H8O6= 176.1232 g/mol) and a starch "filler" which holds them...
Vitamin C tablets contain ascorbic acid (C6H8O6= 176.1232 g/mol) and a starch "filler" which holds them together. Your goal today is to determine how much vitamin C or ascorbic acid, HC6H7O6 is present in the tablet. This can be determined by titrating ascorbic acid, HC6H7O6 with calcium hydroxide solution, Ca(OH)2(aq) (74.0918 g/mol) according to the following equation: 2HC6H7O6(aq) + Ca(OH)2(aq) ---> Ca(C6H7O6)2(aq) + 2H2O(l) First you must make 500 mL of a 0.1012 M standard solution of Ca(OH)2 from a...
Consider the following hypothetical reaction: A + 3B ⇄ 2C + D A titration was performed...
Consider the following hypothetical reaction: A + 3B ⇄ 2C + D A titration was performed in which a standardized solution of A was used as the titrant, and an unknown amount of B was the analyte. The concentration of A in the standardized solution was 0.2005 M (± 0.4%). The initial buret reading was 2.45 mL, and the final buret reading (at the endpoint) was 42.06 mL a) How many moles of B were present in the unknown sample?...
Determining vitamin c lab For two samples which were apple juice and lime juice. Did not...
Determining vitamin c lab For two samples which were apple juice and lime juice. Did not extract because foods were liquids. Titrated with DCIP. Titration for apple juice was total amount of DCIP 10.33ml. How do I set up this problem to get vitamin c per ml solution??? Also standard titration of DCIP was 2.5 mg vitamin c / 13.38 ml DCIP= 0.187 mg vit c/ ml DCIP
Analogy to the Vinegar Analysis We analyze a vitamin C tablet for ascorbic acid, a weak...
Analogy to the Vinegar Analysis We analyze a vitamin C tablet for ascorbic acid, a weak acid with a molar mass of 176.13 g/mole. Once crushed and dissolved in water, it titrates to a nice phenolphthalein/peach-colored endpoint in a 1:1 reaction with sodium hydroxide. A single tablet of 0.607 g is titrated to endpoint against 0.1120 M sodium hydroxide solution. The initial volume of sodium hydroxide titrant is 0.34 mL, and at endpoint the volume is 26.38 mL. Use this...
Procedure Preparation of Reagents 1. Starch indicator will be provided 2. Solid potassium iodide will be...
Procedure Preparation of Reagents 1. Starch indicator will be provided 2. Solid potassium iodide will be available 3. 0.3 M H2SO4 will be available 4. ~0.04 M Sodium thiosulfate solution will be provided. You should be able to complete the experiment with 250 mL of this solution. 5. Preparation of 0.01M KIO3 Solution: a. Accurately weigh approximately 0.535 g of solid reagent and record the mass to 4 decimal places. b. Deliver the KIO3 to a 250 mL volumetric flask...
A student crushed a vitamin C tablet that weighed 1.532g, and transferred 1.489 g of the...
A student crushed a vitamin C tablet that weighed 1.532g, and transferred 1.489 g of the powder into a 100mL volumetric flask. After diluting to the 100.00 mL mark, they tot rated a 20.00 mL aliquot of this solution against .0105 M KIO3 (the KIO3) with an excess of HCl and KI. The initial burst reading was .03 mL; the final buret reading was 18.91 mL. Perform the following calculations: 1. Volume of KIO3 used 2. Mmol of KIO3 used...
A 125 mL sample of orange juice was titrated using a redox reaction to the equivalence...
A 125 mL sample of orange juice was titrated using a redox reaction to the equivalence point with the addition of 7.6 mL of a 0.0025M iodine (I2) solution. What is the concentration of vitamin C (C6H8O6) in this sample? C6H8O6(aq) + I2(aq) ® C6H6O6(aq) + 2I–(aq) + 2H+(aq)
1) What does it mean to be a reducing agent? What ion does vitamin C reduce...
1) What does it mean to be a reducing agent? What ion does vitamin C reduce in this experiment? Explain your answer using the oxidation numbers. b) If you look at the chemical reaction for this experiment, sodium bicarbonate is not a part of the reaction. If so, why do we need to add sodium bicarbonate during the analysis of vitamin C? Explain your answer using balanced chemical equation c) Identify the oxidizing agent in chemical equation (i) from the...
ADVERTISEMENT
Need Online Homework Help?

Get Answers For Free
Most questions answered within 1 hours.

Ask a Question
ADVERTISEMENT