Distillation, recrystallization, chromatography, and extraction techniques used in a college organic chemistry lab.
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- What is the purpose of distillation?
- To separate and purify volatile liquids based on differences in boiling points.
- What is the boiling point of a pure substance?
- The temperature at which the vapor pressure of a liquid equals atmospheric pressure.
- When would you use fractional distillation instead of simple distillation?
- When separating liquids with boiling points less than 25 degrees Celsius apart.
- Why is vacuum distillation used?
- 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?
- To condense vaporized organic compounds back into liquid form.
- What is the purpose of a thermometer adapter in a distillation apparatus?
- 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?
- To maximize heat transfer and prevent air pockets that reduce cooling efficiency.
- What is the purpose of a boiling stone in distillation?
- To provide nucleation sites for smooth, even boiling and prevent violent bumping.
- What does the head temperature measure during a distillation?
- The temperature of vapors at the distillation head, which should equal the boiling point of the product.
- What is recrystallization used for?
- 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?
- 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?
- 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?
- 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?
- To heat the solvent and compound to boiling to ensure complete dissolution.
- What is the scratching technique in recrystallization?
- Scraping the inner wall of a cooling solution with a glass rod to initiate crystal nucleation.