Gas Nonideality at One Atmosphere Revealed Through Speed of Sound Measurements and Heat Capacity Determinations.

• Autores: Arthur M. Halpern, Allen Liu
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 85, Nº 11, 2008, págs. 1568-1570
• Idioma: inglés
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• Resumen

  • Using an easy-to-make cylindrical resonator, students can measure the speed of sound in a gas, u, with sufficiently high precision (by locating standing-wave Lissajous patterns on an oscilloscope) to observe real gas properties at one atmosphere and 300 K. For CO2 and SF6, u is found to be 268.83 and 135.25 m s�1, respectively, versus their ideal-gas (zero-pressure) values of 270.15 and 136.67 m s�1. These differences arise from intermolecular interactions. It is shown that if the molar isobaric heat capacities, Cp, m, are calculated from the one atmosphere u values assuming perfect gas behavior, significant errors are produced. For CO2 and SF6 these errors are 2.7% and 25%, respectively. Experimental Cp, m values are compared with those obtained based on the equipartition theorem.