Question

1. Draw the structure of caffeine indicating its molecular formula (CwHxNyOz) and molar mass.

2. On the average, people use one teaspoon (2.50 g) of instant tea to make an 8-oz glass of iced tea. The average glass of iced tea contains 10 mg of caffeine per oz. (a) Calculate the mass percent of caffeine in a glass of iced tea.

3. A student extracted 1.15 g of crude caffeine from 110.0 g of tea powder. After purification, he obtained 0.70 g of pure caffeine. Calculate the percent recovery of caffeine based on crude caffeine.

Answer 1

Structure of Caffeine Ctz Formula 2- a/mol 19 4 19 9 Molax mass- to ma of affeine 2. Glass of iced +ea per o2 There fore 8-02 Caffeine Contains la ss of iced tea Contains 86 mg pex cent of Gffiene in a iced tea - Amount «f affieue(wt g- Am ouu of ihstant tea| 8, Now lass 3-20% Frow 15 of rude affeine 0.70 pure affeine is etracted L percent of veover here tor wt of pure aflene ) Xio0 wf. f Crude affiene (g % £8 09