ERIC Number: EJ1114004
Record Type: Journal
Publication Date: 2016-Sep
Abstractor: As Provided
Determining the Enthalpy of Vaporization of Salt Solutions Using the Cooling Effect of a Bubble Column Evaporator
Fan, Chao; Pashley, Richard M.
Journal of Chemical Education, v93 n9 p1642-1646 Sep 2016
The enthalpy of vaporization (?H[subscript vap]) of salt solutions is not easily measured, as a certain quantity of pure water has to be evaporated from a solution, at constant composition, and at a fixed temperature and pressure; then the corresponding heat input has to be measured. However, a simple bubble column evaporator (BCE) was used as a novel method that allowed undergraduate students to determine the ?H[subscript vap] value of a salt solution within an hour or so, because it only required temperature measurement (at a steady state) of the column solution and the inlet gas flowing into the column. In this article, by way of illustration, the ?H[subscript vap] value of a 0.5 M NaCl solution was determined using the BCE process. In this experiment the evaporative cooling effects of the column were also easily demonstrated, as the inlet air at room temperature cooled the column solution to less than 10°C. The change that students measured directly demonstrated the endothermic process of water vaporization. The role of several basic physical chemistry concepts, such as vapor pressure, phase transition, and enthalpy, involved in this experiment can be reinforced. An unexpected property of some common salt solutions, of bubble coalescence inhibition, was also observed in this experiment.
Descriptors: Undergraduate Students, Laboratory Experiments, Thermodynamics, Kinetics, Science Materials, Teaching Methods, Scientific Concepts, Scientific Principles, Chemistry
Division of Chemical Education, Inc and ACS Publications Division of the American Chemical Society. 1155 Sixteenth Street NW, Washington, DC 20036. Tel: 800-227-5558; Tel: 202-872-4600; e-mail: email@example.com; Web site: http://pubs.acs.org/jchemeduc
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education; Postsecondary Education
Authoring Institution: N/A
Grant or Contract Numbers: N/A