Oxygen Bleach under the Microscope: Microchemical Investigation and Gas-Volumetric Analysis of a Powdered Household Product

Abstract

A closer look at particles of a solid oxygen-based bleach household product is proposed, both figuratively and literally, to help develop observation and critical thinking skills and to link everyday life to chemistry concepts like acid–base equilibrium, redox reactivity, gas laws, gas volumetry, stoichiometry, and morphology of a heterogeneous solid mixture. In a microchemical approach, students learn to discriminate particles by their morphology under an optical (or low-cost USB) microscope and to investigate how they react with (a) hypochlorite solution (or household chlorine bleach); and (b) acetic acid (or vinegar). Aware of the ingredients listed on the product’s label, and searching for the structure and formula of percarbonate (2Na2CO3·3H2O2), a hydrogen peroxide–sodium carbonate adduct, they end up concluding that the particles showing effervescence with both reagents consist of sodium percarbonate, and those bubbling only in contact with acetic acid are sodium carbonate, while other minor ingred...