Volume 10, Issue 4

Biological Fuel Cells with Drugstore Products
Original Research
The term fuel cell is used to describe an enormous variety of different systems. In addition to hydrogen, other fuels and various catalysts can be used, thus opening up a wide range of applications. If microorganisms or enzymes are used as catalysts, the systems are referred to as biological fuel cells [1]. So far, they are underrepresented at school [2]. To give an impulse to teachers, here we present simple hands-on experiments on biological fuel cells with baker´s yeast [3], lactic acid bacteria and lactase as biocatalysts for students in grades nine to twelve. As these three biocatalysts are drugstore products, the experimental set-ups are low-cost and harmless. Furthermore, the students may already be familiar with the metabolism of yeast or the field of application of lactic acid bacteria and lactase from their everyday lives, so that the working principle of the fuel cells can be easily understood during the experiment.
World Journal of Chemical Education. 2022, 10(4), 149-154. DOI: 10.12691/wjce-10-4-4
Pub. Date: December 27, 2022
1288 Views11 Downloads
Methylene Blue - New Chemistry Experiments for University Education
Original Research
The redox reactions of methylene blue on screen printed electrodes (SPEs) can be measured electrochemically by cyclic voltammetry (CV) and spectroscopically by optical and Raman spectroscopy. The combination of cyclic voltammetry and optical or Raman spectroscopy, known as absorpto- or Raman voltammetry, provides not only electrochemical information about redox reactions at electrodes, but also about changes in the visible and Raman properties of the substances used. Raman scattering can be enhanced by a simple electrochemical in-situ modification; this leads to an electrochemically activated surface enhanced Raman effect (EC-SERS). Therefore, chemical reactions, based on the change in vibrational states of the substances under investigation, can be characterized in a very simple way. In this article, we compare different electrodes and show that the electrochemical reactions of methylene blue strongly depend on the electrodes used. In addition, the electropolymerization of methylene blue is discussed. At the end of the article, a script for students for measuring the spectroelectrochemistry of methylene blue is presented in detail. The didactic background is that the combination of electrochemical information, such as potentials and current fluxes, with spectroscopic information, such as absorption and/or vibrational changes, leads to a better understanding of electrochemistry.
World Journal of Chemical Education. 2022, 10(4), 137-148. DOI: 10.12691/wjce-10-4-3
Pub. Date: November 29, 2022
3112 Views6 Downloads
Improvement of Accuracy and Precision during Simple Distillation of Ethanol-Water Mixtures
Original Research
The simple distillation of ethanol-water mixture is a well-known experimental subject in either general chemistry laboratory or organic chemistry laboratory. The objective is to provide a reliable guidance for college students who are major in chemistry or chemical engineering to obtain repeatable results during the simple distillation of ethanol-water mixture. The liquid-vapor phase diagram of ethanol-water mixtures was introduced before experiment. As similar to a tradition distillation assembly, Liebig condenser, specific gravity hydrometer set, and heating mantle were mainly employed to perform the experiment of a simple distillation with minor but critical changes. The examination of diverse results in distillate amounts and distillate ethanol concentrations were analyzed by Rayleigh equation. The simple distillation was evaluated at the assigned temperature that was selected from liquid-vapor phase diagram. Even though the first evaporation started at a temperature below the theoretical bubble point shown in liquid-vapor phase diagram in most cases, the set temperature was gradually adjusted and maintained until no more vapor generated. In fact, this work motivates students to design their simple distillation plans through changing initial ethanol concentration and set temperature. The experimental data from 23 groups suggest that the accuracy and the precision were dependent upon how to control heating rates and to sustain set temperature in this work.
World Journal of Chemical Education. 2022, 10(4), 131-136. DOI: 10.12691/wjce-10-4-2
Pub. Date: October 30, 2022
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Exploring Potential Energy Surface with Mathematica: An Algorithmic Demonstration of Minimum Energy Path, Stationary Points and Transition State
Original Research
The reaction profile (energy profile) is a widely used conceptual tool in chemical kinetics to represent the progress of a chemical reaction. Quantitatively, a reaction profile can be viewed as a minimum energy path (MEP) on the potential energy surface (PES), which connects the reactants and products through one or more transition states or intermediates. In this article, we used Mathematica program to demonstrate a generic method for finding reaction profile on a Müller-Brown PES by applying steepest descent algorithm. The properties of the MEP and stationary points were discussed in detail. The general characteristics of the transition state (TS), and imaginary mode were illustrated with a vibrational analysis of hydrogen exchange reaction, H2+H → H+H2.
World Journal of Chemical Education. 2022, 10(4), 124-130. DOI: 10.12691/wjce-10-4-1
Pub. Date: September 12, 2022