Oxygen from Hydrogen Peroxide A Safe Molar Volume-Molar Mass Experiment
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John H. Bedenbaugh, Angela 0. Bedenbaugh, and Thomas S. Heard University of Southern Mississippi, Hattiesburg, MS 39406
The manganese dioxide-catalyzed thermal decomposition of potassium chlorate to produce oxygen is the classic molar volume-molar mass experiment that has been found in countless general chemistry laboratory textbooks for decades. However, it is a procedure that is falling into disrepute. The potential hazards inherent in this preparation of oxygen have been listed {1) and reports of explosions occurring during this experiment continue to mount (2). By direct suggestion (3) or implication (4) teachers are being advised not to incorporate this procedure into their program of experiments. Unfortunately, teachers will find only a very limited number of experiments from which to choose a substitute procedure that will accomplish the same instructional objectives (5). Convinced of the hazard of using potassium chlorate, we wanted to develop a specific replacement procedure (one in which a reactant on decomposition would yield oxygen gas quantitatively) for use by students in determining molar volume or molar mass. We sought a method that would be simple, rapid, inexpensive, and in which we could use locally available chemicals. In 1926 Wikoff and Brown (6) published a procedure for the qualitative preparation of oxygen that is rarely cited today. A cake of compressed bakers’ yeast was mixed with water to give a uniform suspension. When a 3% solution of hydrogen peroxide was added to the suspension, a vigorous evolution of oxygen occurred. Bakers’ yeast is exceptionally rich in the enzyme, catalase, which catalyzes the decomposition of hydrogen peroxide to produce oxygen and water. 2H202
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