Question

Caffeine, C8H10O2N4·H2O (FW = 212.1), has been shown to have an average absorbance A = 0.510 for a concentration of 1.000 mg per 100 mL at 272 nm. A sample of 2.500 g of a soluble coffee product was mixed with water to a volume of 500 mL, and a 25-mL aliquot was transferred to a flask containing 25 mL of 0.1 M H2SO4. This was subjected to the prescribed clarification treatment and made up to 500 mL. A portion of this treated solution showed an absorbance of 0.415 at 272 nm. The cuvette used is 1.0 cm in diameter. Calculate the absorptivity (L/g·cm) for caffeine in the problem above. A. 1.08 x 10^4 B. 5.1 x 10^3 C. 51.0 D. 10.8

          Caffeine, C8H10O2N4·H2O (FW = 212.1), has been shown to have an average absorbance A = 0.510 for a concentration of 1.000 mg per 100 mL at 272 nm. A sample of 2.500 g of a soluble coffee product was mixed with water to a volume of 500 mL, and a 25-mL aliquot was transferred to a flask containing 25 mL of 0.1 M H2SO4. This was subjected to the prescribed clarification treatment and made up to 500 mL. A portion of this treated solution showed an absorbance of 0.415 at 272 nm. The cuvette used is 1.0 cm in diameter.

Calculate the absorptivity (L/g·cm) for caffeine in the problem above.

A. 1.08 x 10^4
B. 5.1 x 10^3
C. 51.0
D. 10.8

Added by Pedro M.

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