Exploring Chemical Kinetics at Home in Times of Pandemic: Following the Bleaching of Food Dye Allura Red Using a Smartphone

Abstract

In this communication, a remote experimental activity in chemical kinetics is described, taking into account the quantification based on the optical sensor of a smartphone. The objective pursued herein is to equip students with the appropriate tools and strategies required to empirically determine the parameters of the rate law including reaction orders, rate constant (k), frequency factor (A), and activation energy (Eₐ). Typical results of the proposed protocol are shown and discussed in the framework of the bleaching reaction of food dye allura red (RD40) and hypochlorite, as a representative example. A graphical approach of the concentration vs time data measured under the experimental condition where [RD40] ≪ [ClO⁻] (isolation method) suggests a first-order kinetics with respect to the dye. In addition, the analysis of the pseudo-first-order constant (k_obs) shows a first-order relationship with respect to ClO⁻. In addition, using the two-point form of the Arrhenius equation, values of 3.22 × 10⁷ s/M and 44.55 kJ/mol were obtained for A and Eₐ, respectively. Interestingly, all the kinetic parameters (reaction orders, k, A, and Eₐ) are on the same order of magnitude as those previously reported in the literature and acquired with more sophisticated and accurate equipment. This experience provides evidence that it is possible to proceed with remote experimental activities to deepen the collection and analysis of kinetic data during a pandemic.