The Teaching of Consecutive First-Order Reaction Kinetics: A Chemical Education Research Study of the Impact of Hands-On Demonstrations

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 13 Issue 3 (2008) pp 131-135

The Teaching of Consecutive First-Order Reaction Kinetics: A Chemical Education Research Study of the Impact of Hands-On Demonstrations

Laura E. Ruebush and Simon W. North*

Department of Chemistry, Texas A&M University, P. O. Box 30012, College Station, Texas 77842, swnorth@tamu.edu
Received July 16, 2007. Accepted September 30, 2007.

Published online: 3 May 2008

Abstract. An instructional sequence has been developed to increase conceptual understanding of a special topic in chemical kinetics, first-order consecutive reactions: where k₁ and k₂ are the rate constants associated with each step, using a sequence of qualitative and quantitative exercises. The qualitative exercise involves aperture-limited water flow through tubes in series to represent interconversion of species involved in the consecutive reaction. Adjusting the ratios of the aperture diameters permits exploration of the limits, k₁>> k₂ and k₂>> k₁. The quantitative activity involves employing a “dice game” to generate random kinetics “data.” The data was subsequently fitted using a preprogrammed Excel workbook using integrated rate laws to determine the relevant rate constants. The focus of this instructional sequence was to link changes in the time-dependent concentrations of species A, B, and C to changes in k₁ and k₂, and to create an environment that allowed discussion of the steady-state approximation without the use of complex mathematics. The instructional sequence was piloted during Cohort III of the Information and Technology in Science (ITS) Center. A similar exercise is now implemented as part of the Texas A&M University First-Year Chemistry Program as part of the laboratory experience. We found that the average participant score from pre- to post-test showed marked improvement (25% to 75%); however, even after instruction some misconceptions remained.

Key Words: In the Classroom; consecutive reactions; demonstration; dice game; information technology; instructional sequence

(*) Corresponding author. (E-mail: swnorth@tamu.edu)

Article in PDF format (189 KB) HTML format

Supporting Materials:

The Excel spreadsheet used in the dice exercise is available (52 KB)