Level: introductory+
Reference: Max Bodenstein, "Gas reactions in chemical kinetics II. Effect of the temperature on the formation and decomposition of hydrogen iodide," Zeitschrift für physikalische Chemie 29, 295-314 (1899).
Notes: Max Bodenstein (1871-1942) was a pioneer in gas-phase kinetics. (Click here for a set of exercises based on his kinetic data.) His experimentation on the hydrogen iodide system was a landmark investigation of careful kinetic and equilibrium measurements over an extended temperature range (more than 200°C). As part of his analysis of these data, Bodenstein computed equilibrium constants for the decomposition of HI as a function of temperature. (In this respect, the exercises are similar to what Bodenstein did.) He fit his data to a multi-parameter equation, though:
ln K = -a/T + b ln T + cT + constant ,where a, b, and c are constants.
Agreement of the standard enthalpy and entropy of reaction from these data with values derived from NIST tables is impressive. The van't Hoff plot of Bodenstein's data exhibits a slight but evident curvature, an opportunity to remind students that standard enthalpies and entropies do change with temperature.
Solutions: To download solutions, go to:
http://web.lemoyne.edu/giunta/classicalcs/bodeneq.doc
To download worked spreadsheet, go to:
http://web.lemoyne.edu/giunta/classicalcs/bodenstein.xls
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