Organic Chemistry I: Extraction of Caffeine from Tea Original Tea Sample: Mass o

Question

Organic Chemistry I: Extraction of Caffeine from Tea

Original Tea Sample:

Mass of tea sample = .99 grams

Extracted Caffeine:

Mass of caffeine= .04 grams

So, .04 grams of caffeine was extracted from .99 grams of a sample of tea.

Questions:

Based on the result given above, which shows that the mass percent of caffeine was 4% in the instant tea sample for this experiment.- please see question 1 (b).

1) On the average, people use 2.5 grams of instant tea to make an 8.0-oz glass of iced tea. The average glass of iced tea contains 10. mg of caffeine per oz.

(a) Based on this information, calculate the mass percent of caffeine in a glass of iced tea.

(b) Are your experimental results consistent with these facts? Briefly explain.

(c) If not, explain why your experimental results may differ from these data.

2) Our experiment used a solution of NaOH (instead of pure water) as the aqueous layer. Explain why using NaOH provides a more complete extraction of caffeine (and other xanthines).

3) Which compound is less soluble in water: Xanthine, Caffeine, Theophylline, or Theobromine?

Thank You in Advance!

Explanation / Answer

1) On the average, people use 2.5 grams of instant tea to make an 8.0-oz glass of iced tea. The average glass of iced tea contains 10. mg of caffeine per oz.

(a) Based on this information, calculate the mass percent of caffeine in a glass of iced tea.

Solution :- lets first calculate the mass of the caffeine in 8 oz iced tea

8 oz * 10 mg / 1 oz = 80 mg

Lets convert mg to gram

80 mg* 1 g / 1000 mg = 0.08 g

Now lets calculate the percent of the caffeine

% caffeine = (mass caffeine / mass of istant tea )*100%

            = (0.08 g/2.5g)*100%

           = 3.2 % caffeine

(b) Are your experimental results consistent with these facts? Briefly explain.

Solution :- The percent of the caffeine obtained in the experiment is little higher than the percent of the caffeine in the instant tea. So the percent of caffeine is not consistant.

(c) If not, explain why your experimental results may differ from these data

Solution :- The percent of the caffeine obtained in the experiment is little higher than the expected this may happened because of the caffeine sample is not dried well which causes moisture to remain in it which gives higher mass of caffeine than actual and increases the percent of the caffeine or it may also contain some impurities which added up to the mass of the caffeine which gives the higher percent of the caffeine.

2) Our experiment used a solution of NaOH (instead of pure water) as the aqueous layer. Explain why using NaOH provides a more complete extraction of caffeine (and other xanthines).

Solution :- If any acid is used to form the salt of the caffeine which makes it soluble in water then that excess acid is neutralized by the NaOH and it also helps to form the precipitate of the caffeine and separated it from the water. Therefore NaOH is used in the experiment.

3) Which compound is less soluble in water: Xanthine, Caffeine, Theophylline, or Theobromine?

Solution :- Caffeine is more soluble than the other compounds.

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