Relating ΔHvap of Organic Liquids to Intermolecular Forces: Simple Modifications of a Classic General Chemistry Experiment
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[1] Naval Academy
Naval Academy
Turquía
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- Localización: Journal of chemical education, ISSN 0021-9584, Vol. 97, Nº 5, 2020, págs. 1406-1410
- Idioma: inglés
- Texto completo no disponible (Saber más ...)
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Resumen
The concept of equilibrium vapor pressure plays a key role in the general chemistry curriculum; it is among the first and most easily demonstrated examples of equilibrium and frequently caps off the first semester of general chemistry where it illustrates the properties of liquids and intermolecular forces. We report here simple modifications of Levinson’s classic experiment that allow measurement of vapor pressures for organic samples at a variety of temperatures. Data analysis gives heats of vaporization which may be interpreted in terms of intermolecular attractive forces. Equipment needs are simple and readily available: a 10 mL graduated cylinder, a tall 1 L beaker, disposable graduated syringes, and a 10 in. needle or cannula bent into a “J” shape. The method uses 1 mL or less of organic sample per trial and works well for organic liquids that are immiscible with and are less dense than water. Student results are presented for the experiment conducted over three semesters as well as the impact on student learning as assessed by common exam results and end-of-semester student surveys.
