Caffeine, C8H10O2N4 H2O (MW = 212.2 g/mol) has been shown to have an average absorbance of 0.644 for a concentration of 1.783 mg per 100 mL at 272 nm. A sample of 3.658 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 0.666 at 272 nm. Assumbe b = 1.0 cm. Calculate the % caffeine (w/w) in the sample.
Caffeine, C8H10O2N4 H2O (MW = 212.2 g/mol) has been shown to have an average absorbance of 0.644 for a concentration of 1.783 mg per 100 mL at 272 nm. A sample of 3.658 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 0.666 at 272 nm. Assumbe b = 1.0 cm. Calculate the % caffeine (w/w) in the sample.
Principles of Modern Chemistry
8th Edition
ISBN:9781305079113
Author:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler
Publisher:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler
Chapter20: Molecular Spectroscopy And Photochemistry
Section: Chapter Questions
Problem 6P
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Caffeine, C8H10O2N4 H2O (MW = 212.2 g/mol) has been shown to have an average absorbance of 0.644 for a concentration of 1.783 mg per 100 mL at 272 nm. A sample of 3.658 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 0.666 at 272 nm. Assumbe b = 1.0 cm.
Calculate the % caffeine (w/w) in the sample.
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Step 1: Write the Lambert-Beer's law
VIEWStep 2: Calculate the molar absorptivity of caffeine
VIEWStep 3: Draw the flow chart of preparation of solution
VIEWStep 4: Determine the concentration of solution-C
VIEWStep 5: Determine the concentration of solution- B
VIEWStep 6: Determine the % caffeine in the sample
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