An undergraduate experience for studying the diffusion of a solute in an aqueous solution

Molecular diffusion driven by concentration gradients is the most common type of diffusion in chemical separation processes, such as liquid-liquid extraction, stripping, and adsorption. To better understand molecular diffusion, a fundamental knowledge of Fick’s law of diffusion is crucial. In the Spring 2021 semester, I participated in the Special Problem Course offered by Dr. Souto, in which we developed a new undergraduate laboratory experience. This experience consisted of a hands-on experimental work and data analysis to study the diffusion of salt in an aqueous media. This new experiment will be incorporated in the Chemical Engineering Senior Laboratory in the Fall 2021 semester, where currently, there are no experiments for students to study molecular diffusion. This project was funded by the 2020 AIChE Separations Division Education and Outreach award. The work consisted of preparing a concentrated sodium chloride solution, arming the equipment set-up, collecting and analyzing the data. Additionally, we prepared the experimental handout and a video demonstration. This video demonstration could also be useful in other chemical engineering courses. Also, during summer 2021, we expanded this project to study the repeatability of the experiment. We performed multiple experimental runs at different concentrations of sodium chloride (1 M and 2 M). The diffusion