Determination of Al Content in Commercial Samples through Stoichiometry: A Simple Experiment for an Advanced High-School Chemistry Olympiad Preparatory Course

Abstract

Stoichiometry has always been a puzzling subject. This may be partially due to the way it is introduced to students, with stoichiometric coefficients usually provided in the reaction. If the stoichiometric coefficients are not given, students find it very difficult to solve problems. This article describes a simple 4-h laboratory experiment for the determination of aluminum content in commercial samples through the stoichometric relationship between aluminum and released hydrogen gas. The experiment was performed by highschool students at an advanced preparation course for the Chemistry Olympiad. The aluminum content in foil samples was determined by measuring the amount of formed hydrogen gas through mass balance of the reaction system. The experiment is appropriate for high-school chemistry or a first-semester general chemistry course."We may lay it down as an incontestable axiom, that, in all operations of art and nature, nothing is created; an equal quantity of matter exists both before and after the experiment; the quality and quantity of elements remain precisely the same; and nothing takes place beyond changes and modifications in the combination of these elements." 1

All Roads Lead to Rome: Triple Stoichiometry with a Lithium Battery

“…To reinforce its concepts, experiments are continuously designed so that students can better understand molar ratios from a practical standpoint. For example, in the past decade, the Journal of Chemical Education published papers on the subject whereby the favorite techniques to ascertain stoichiometric relationships included mainly colorimetry/spectrophotometry, − conductivity, , electrochemistry, − gravimetry, − titrimetry, , gas generation, − thermochemistry/thermal analysis, , − and catalysis …”

Obtaining and Investigating Amphoteric Properties of Aluminum Oxide in a Hands-On Laboratory Experiment for High School Students

“…Demonstrating those properties plays a key role when discussing periodic changes of acid–base properties of elements and their compounds. In the case of aluminum and aluminum hydroxide, the properties may be demonstrated by carrying out simple experiments. , Unfortunately, presenting the amphoteric properties of aluminum oxide is more complicated. It should react according to the following reactions: Unfortunately, not all polymorphic forms of aluminum oxide have these amphoteric properties .…”

“…In the case of aluminum and aluminum hydroxide, the properties may be demonstrated by carrying out simple experiments. 1,2 Unfortunately, presenting the amphoteric properties of aluminum oxide is more complicated. It should react according to the following reactions: 2…”

Model Experiment of Thermal Runaway Reactions Using the Aluminum–Hydrochloric Acid Reaction

“…Although learning about the mechanism of thermal runaway reactions and their prevention through laboratory exercises would be effective for safety education, it is not possible to employ such hazardous reactions as experiments in student laboratories. In this study, a laboratory exercise designed to teach students about thermal runaway reactions is proposed using a reaction between an aluminum (Al) and hydrochloric acid (HCl­(aq)) that is widely used in chemistry education. , The serious accident due to thermal runaway in an Al–AlCl 3 –HCl­(aq) system has also been reported . In an open system, however, this reaction can act as a pseudothermal runaway reaction for which explosion and ignition are not a concern.…”

“…In this study, a laboratory exercise designed to teach students about thermal runaway reactions is proposed using a reaction between an aluminum (Al) and hydrochloric acid (HCl(aq)) that is widely used in chemistry education. 7,8 The serious accident due to thermal runaway in an Al−AlCl 3 − HCl(aq) system has also been reported. 9 In an open system, however, this reaction can act as a pseudothermal runaway reaction for which explosion and ignition are not a concern.…”