Distillation, recrystallization, chromatography, and extraction techniques used in a college organic chemistry lab.
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- What is the purpose of distillation?
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To separate and purify volatile liquids based on differences in boiling points.- What is the boiling point of a pure substance?
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The temperature at which the vapor pressure of a liquid equals atmospheric pressure.- When would you use fractional distillation instead of simple distillation?
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When separating liquids with boiling points less than 25 degrees Celsius apart.- Why is vacuum distillation used?
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To lower the boiling point of heat-sensitive compounds that would decompose at atmospheric pressure.- What is the primary purpose of a water-cooled condenser in distillation?
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To condense vaporized organic compounds back into liquid form.- What is the purpose of a thermometer adapter in a distillation apparatus?
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To position the thermometer bulb at the side arm level to accurately measure the temperature of distillate vapors.- Why must the condenser jacket be filled completely with coolant?
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To maximize heat transfer and prevent air pockets that reduce cooling efficiency.- What is the purpose of a boiling stone in distillation?
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To provide nucleation sites for smooth, even boiling and prevent violent bumping.- What does the head temperature measure during a distillation?
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The temperature of vapors at the distillation head, which should equal the boiling point of the product.- What is recrystallization used for?
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To purify solid organic compounds by dissolving them in hot solvent and reforming pure crystals upon cooling.- What properties should an ideal recrystallization solvent have?
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High solubility of the compound when hot, low solubility when cold, and low toxicity.- What is the difference between a hot and cold solvent in recrystallization?
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A hot solvent dissolves the crude compound; a cold solvent causes pure crystals to precipitate.- Why is slow cooling preferred over rapid cooling in recrystallization?
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Slow cooling produces large, pure crystals; rapid cooling creates many tiny crystals and includes impurities.- What is the role of a hot plate in recrystallization?
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To heat the solvent and compound to boiling to ensure complete dissolution.- What is the scratching technique in recrystallization?
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Scraping the inner wall of a cooling solution with a glass rod to initiate crystal nucleation.
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