Caffeine occurs naturally in tea leaves and coffee beans. Pure caffeine (mp 236d

Question

Caffeine occurs naturally in tea leaves and coffee beans. Pure caffeine (mp 236degreeC) is a white crystalline solid material at room temperature. It is classified as an alkaloid - a nitrogen-containing basic compound that is obtained from plants and has physiological effects. A student pulverizes 4.01 grams (g) of coffee beans into a finely ground powder by using a mortar and pestle. The caffeine is then extracted into 275 mL of boiling dichloromethane (CH_2Cl_2) After 30 minutes, the solution is filtered hot to remove a large amount of brown insoluble material. Dichloromethane is removed from the filtrate via distillation, leaving 68.6 milligrams (mg) of caffeine behind, as a white solid. What is the percentage of isolated caffeine with respect to the starting amount of crude coffee beans?

Explanation / Answer

Amount of crude coffee beans taken = 4.01 g

caffeine isolated = 68.5 mg = 0.0686 g

Percentage of caffaine isolated with respect to crude coffee beans = (0.0686/4.01)*100 = 1.71%

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