Rethinking the Squeaky Pop Test–A Novel Hydrogen Test for Chemistry Classes (Journal Article)

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Abstract: In school chemistry, the oxyhydrogen or “Knallgas” reaction is used to provide evidence of hydrogen gas in the squeaky pop test. However, the test actually indicates the presence of an explosive gas mixture of hydrogen and oxygen (oxyhydrogen gas) rather than pure hydrogen. The sheer observations of an explosive reaction and the formation of a condensing reaction product, which can be detected as water, are not sufficient to call the squeaky pop test a clear and specific test for hydrogen. These observations can also be made by burning gaseous hydrocarbons with stoichiometric amounts of oxygen, contradicting the assumption that the gas present in the reaction vessel is a mixture of hydrogen and oxygen. For a reliable detection of hydrogen, this article presents the preparation of a heterogeneous catalytic system which facilitates a specific and unambiguous hydrogen test in chemistry classes by using a redox dye for the clearly visible indication of hydrogen: the Heterogeneous Catalyzed Hydrogen Test (HeCHT). The catalyst can be synthesized easily and safely due to the low hazard potentials of the reactants and products. Furthermore, the preparation of the test reagent is inexpensive, and the reagent can be reused.