CHEM Lab 8 Organic Chemistry Provide the expected melting point of caffeine and the boiling points of dichloromethane, ethanol, acetic acid and ethyl acetate. (5 pts.)
MP Caffeine: 234.2°C-236.3°C
BP DCM: 103.6°C-107.5°C
BP Ethanol: 72.3°C-75.3°C
BP Acetic Acid: 117.8°C-118.9°C
BP Ethyl Acetate: 77.1°C
Provide an outline on how to perform a recrystallization. (10 pts.) Recrystallization is a procedure for purifying an impure compound in a solvent. The method of purification is based on the principle that the solubility of most solids increases with increased temperature. This means that as temperature increases, the amount of solute that can be dissolved in a solvent increases. As the solvent cools, the solution becomes saturated with the solute and the solute crystallizes out (a solid). As the crystal develops, impurities are excluded from the crystal lattice, thereby completing the purification process. The crystals can then be collected, washed, and dried. 1 / 2
Complete the following based on the video you watched: (11x 2 = 22 pts.)
Isolation of caffeine from tea leaves in the lab involved a Solid-liquid extraction followed by a Liquid-liquid extraction Mass of tea leaves used10.0 g Mass of calcium carbonate used4.00 g Moles of calcium carbonate used0.04 mol Crude weight of extracted caffeine161mg Melting point of extracted, crude caffeine 212.1°C-225.6°C Melting point of extracted, recrystallized caffeine 233.9°C-235.2°C Expected melting point of pure caffeine 234.2°C-236.3°C During the extraction you noticed two distinct (top and bottom) layers: which one of them is the dichloromethane layer? Which property of dichloromethane was responsible for this observation? (4 pts.)
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