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A problem-based online learning (PBe-L) teaching sequence was designed for calculating the shelf life (expiration date) of an on-site solution of refrigerated drug as part of activities of a Pharmaceutical Physical Chemistry course of Pharmacy major at FES Cuautitlán UNAM in Mexico. The teacher presents students the problem, a group collaborative activity is carried out to search for information in PBL cycles. Students are then shown a virtual experiment that includes experimental results. Another group collaborative activity is carried out for the search of information, for the procedural analysis of the results. Applying knowledge and understanding of the topics of chemical kinetics, temperature effect on the rate of chemical reactions and drug degradation reactions, etc., students solve the problem. Hake's factor was determined for the conceptual gain. A Likerttype satisfaction survey was conducted and compared to the results of a group that was applied to the PBL strategy in person. At the end of the sequence students achieved recognition, comprehension and application learnings and conceptual gain was high. Allowing an integration of its cognitive framework of kinetics topics.

El objetivo del presente trabajo es ayudar a lograr aprendizajes significativos y mejor comprensión por parte de los estudiantes que cursan Cinética Química y Principios de Diseño de Reactores en carreras del área de química. Se presenta una estrategia didáctica empleando el solver de Excel para la solución analítica de un sistema de ecuaciones generadas para la determinar el tamaño óptimo de reactores CSTR que operan en serie de manera isotérmica e isobárica. El procedimiento involucra conocer la conversión intermedia lograda por cada reactor para determinar del volumen óptimo de cada unidad, el cual es descrito por el método de la maximización del área de rectángulos sobre la curva de Levenspiel la cual es extrapolable a “n” unidades de reactores, a diferencia del método gráfico, que es iterativo y solamente práctico hasta tres unidades

In order to teach students, the importance of conductometric titrations in this work, we present a laboratory experiment to quantify the amount of metformin hydrochloride in a tablet. The quantification was carried out through the evaluation of the chloride by silver nitrate. The titration and the end point were followed by conductometric titration, as well as by potentiometric and visually by the Volhard method. In addition, the theoretical conductivities of the metformin hydrochloride solution were calculated when known volumes of titrant are added, using the limit conductivity data for each of the ions present in the literature. To simulate the conductometric titration, the calculated conductivity values were plotted based on the volume of silver nitrate added. A comparison between techniques is made in order to determine the best monitoring method, being this one conductimetry to detect the equivalence point for metformin hydrochloride with 0.99±0.03, according to relative standard deviation (% RSD). Simulated titration curves adequately describe obtained results in an experimental way. The conductometric titration is the best method for quantification since it shows less dispersion between obtained results and has the highest concordance among results. Their application is shown through the analysis and conductometric titration simulations.