Level: introductory
Reference: Joseph Louis Gay-Lussac, "Memoir on the Combination of Gaseous Substances with Each Other," Mémoires de la Société d'Arcueil 2, 207ff (1809)
Notes: Joseph-Louis Gay-Lussac (1778-1850) carried out important research on the physical and chemical properties of gases. He helped establish that the volume of a gas at constant pressure varies simply with its temperature (Gay-Lussac 1802), a result known today as Charles' law. His study of gases was not confined to the laboratory: he ascended several thousand meters in a baloon to make meteorological and magnetic measurements, and to collect samples of gas for chemical analysis. His work on the acids hydrogen fluoride, hydrogen chloride, hydrogen iodide, and hydrogen cyanide led to the realization that acids need not contain oxygen. He was also the first to isolate the element boron. These exercises deal with the combining volumes of gases, that is, the ratios by volume in which gases react.
Gay-Lussac's main conclusion in this paper was that gases combine in simple ratios by volume. Some of the data from which he drew this conclusion were observations (by himself and others) of gases' combining volumes. Some of the data were combining masses (such as those used in this problem), which he converted to volumes. Gay-Lussac used gas densities to combine masses to volumes, however, not (as in this exercise) molar masses and the ideal gas law, neither of which were available at that time. Gay-Lussac's conclusion was consistent with the idea, recently advanced by John Dalton, that reactions occured in simple ratios by atom (or molecule). Of course, the data in this problem support the concept that reactions take place in simple molar ratios. Since moles are proportional to molecules, they also support the concept of combination by simple ratios of molecules.
Further information: A detailed summary of key primary literature on multiple proportions, the atomic hypothesis, and atomic weights, including some quantitative treatment of data may be found in Leonard Nash, "The Atomic-Molecular Theory," in James Bryant Conant, ed., Harvard Case Histories in Experimental Science, vol. 1 (Cambridge, MA: Harvard, 1957), pp. 215-321.
Solutions: To download solutions, go to:
http://web.lemoyne.edu/giunta/classicalcs/GAYvolumes.doc
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