The hydrogenation of alkenes by heterogeneous catalysts has been studied for 80 years. The foundational mechanism was proposed by Horiuti and Polanyi in 1934 and consists of three steps: (i) alkene adsorption on the surface of the hydrogenated metal catalyst, (ii) hydrogen migration to the beta-carbon of the alkene with formation of a delta-bond between the metal and alpha-C, and finally (iii) reductive elimination of the free alkane. Hundreds of papers have appeared on the topic, along with a number of variations on the Horiuti-Polanyi mechanism. The second step is highly reversible, leading to extensive deuterium-hydrogen exchange when D[subscript 2](g) is used. This paper describes the investigation of gas-phase reactions between deuterium and 1-butene using a supported palladium catalyst under ambient laboratory conditions and how the results are consistent with the Horiuti-Polanyi mechanism. An Excel spreadsheet for modeling the extent and distribution of deuteration within butane-d[subscript x] is described. Interested readers could develop a laboratory or research experience based on results presented here. The results are also suitable for inclusion in an upper-division chemistry course in which organometallic chemistry or reaction mechanisms involving heterogeneous catalysts are discussed. The catalyst tubes are inexpensive and easy to construct. Analysis of the butane produced by [superscript1]H NMR and GC-MS leads to numerous conclusions in support of the Horiuti-Polanyi mechanism. (Contains 9 figures.)