Determination of Reaction Stoichiometry by Applying Job’s Method and Digital Image Processing for Precipitation Reactions

Abstract

Herein we present a simple test tube experiment to demonstrate the application of Job’s method for the determination of reaction stoichiometry in high school or university students’ laboratory practices. Various precipitation reactions, all yielding white precipitates and thus serving as perfect unknown systems for students, are applied to observe different stoichimetric ratios. The evaluation relies on digital image processing (ImageJ) based determination of the height of precipitate columns in test tubes. The mole fraction belonging to the highest amount of product is obtained using a commercial spreadsheet editor (MS Excel). The experiments are safe, robust, and inexpensive, and the measurements can be carried out by using a simple ruler if digital image processing is not available.