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The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 19 (2014) pp 034-038

An Adiabatic Expansion Experiment Done On A Budget

Jason Hofstein*, Michael Perry, and Daniel McCabe

Department of Chemistry and Biochemistry, Siena College, Loudonville, NY 12211, jhofstein@siena.edu
Received December 14, 2013. Accepted January 23, 2014.

Published: 20 February 2014

Abstract. Using two different experimental setups to achieve a simple adiabatic expansion of a gas, the ratio of constant pressure to constant volume heat capacities for several gases was measured. In the first setup, an 18-L carboy was insulated, fitted with a ported rubber stopper to control gas flow, and filled with a particular gas. The expansion was achieved manually by quickly raising and lowering a rubber stopper at the mouth of the carboy. The pressure of the system was monitored during this process using a Vernier gas pressure sensor, and data was collected using Vernier’s Logger Pro 2.2.1. In the second setup, a PVC gate valve was used to quickly release the gas pressure and begin the expansion, and data was collected using Vernier’s Logger Pro 3.4.5. Acquired data from both set ups were very similar and values of the ratio of heat capacities for argon, air, nitrogen, and carbon dioxide agreed well with reference values. By using Vernier probes and software, as well as using low-cost alternatives for equipment, the operating costs and complexity of experimental procedures were significantly reduced. As a junior-level, undergraduate physical chemistry experiment, students were exposed to fundamental thermodynamic properties of gases, instrumentation, and simple data acquisition.

Key Words: Laboratories and Demonstrations; physical chemistry; upper-division undergraduate; graduate education/research; laboratory instruction; problem solving/decision making; atmospheric chemistry; calibration; gases; molecular properties/structure; physical properties; thermodynamics; undergraduate research.

(*) Corresponding author. (E-mail: jhofstein@siena.edu)

Article in PDF format (67 KB) HTML format

Supporting Materials:

Several pages of material are available, including a historical account of the evolution of the experiment, instructor references on the background thermodynamics and the derivation of girreversible , the procedure from last year’s lab handout (420 KB)



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