World Journal of Chemical Education

We propose a more general wording for Madelung rule using a new descriptor based on the four quantum numbers n, ℓ, mℓ, ms of the most recently added electron notes K(ZX). By this formulation, K(ZX) will increment as the atomic number Z increases. No exceptions will remain. It can be connected to the first ionization energy.

World Journal of Chemical Education. 2015, 3(6), 160-167. DOI: 10.12691/wjce-3-6-5
Pub. Date: January 03, 2016

Full-Text PDF

17633 Views6502 Downloads5 Likes

An Educational Activity: Building a MRPC

by Lucia Garritano, Angela Milazzo and Marco Schioppa

Original Research

This paper describes a teaching laboratory activity conducted at the high school "E. Fermi" of Catanzaro (Italy), within the Extreme Energy Events (EEE) Project, together with an analysis of the obtained results. In Italy the experiment studying cosmic rays is called the EEE Project and is, currently, carried out by a collaboration of several research institutes like Centro Fermi, INFN, CERN and MIUR (the Italian Ministry of Education, University and Research). The project uses telescopes in different secondary schools of the Italian territory for the study of extensive air showers of high-energy cosmic rays through the revelation of the muon component. The telescope consists of three MRPC (Multigap Resistive Plate Chambers). The aim of this educational is to build a model of the above simplified chamber for an improved understanding of its operation and the associated physical-chemical principles.

World Journal of Chemical Education. 2015, 3(6), 150-159. DOI: 10.12691/wjce-3-6-4
Pub. Date: January 03, 2016

Full-Text PDF

24990 Views7497 Downloads2 Likes2 Citations

Teaching Thermodynamic, Geometric and Electronic Aspects of Diels-Alder Cycloadditions by Using Computational Chemistry – An Undergraduate Experiment

by Norberto K. V. Monteiro and Caio L. Firme

Original Research

We have appliedan undergraduate minicourse of Diels-Alder reaction in Federal University of Rio Grande do Norte. By using computational chemistry tools (Gaussian, Gaussview and Chemcraft) students could build the knowledge by themselves and they could associate important aspects of physical-chemistry with Organic Chemistry. They have performed a very precise G4 method for the quantum calculations in this 15-hour minicourse. Students were taught the basics of Diels-Alder reaction and the influence of frontier orbital theory on kinetics. They learned how to use the quantum chemistry tools and after all calculations they organized and analyzed the results. Afterwards, by means of the PhD student and teacher guidance, students discussed the results and eventually answered the objective and subjective questionnaires to evaluate the minicourse and their learning. We realized that students could understand the influence of substituent effect on the electronic (and kinetic indirectly), geometric and thermodynamic aspects of Diels-Alder reactions. Their results indicated that Diels-Alder reactions are exergonic and exothermic and that although there is an important entropic contribution, there is a linear relation between Gibbs free energy and enthalpy. They learned that electron withdrawing groups in dienophile and electron donating groups in diene favor these reactions kinetically, and on the other hand, the opposite disfavor these reactions. Considering thermodynamically controlled Diels-Alder reactions, the EDG decrease the equilibrium constant, in relation to reference reaction, unlike the EWG. We believe that this minicourse gave an important contribution for Chemistry education at undergraduate level.

World Journal of Chemical Education. 2015, 3(6), 141-149. DOI: 10.12691/wjce-3-6-3
Pub. Date: December 05, 2015

Full-Text PDF

24322 Views7234 Downloads1 Likes

Spectroscopic and Electrochemical Investigations of N-(Phosphonomethyl)glycine (glyphosate) and (Aminomethyl)phosphonic Acid (AMPA)

by A. Habekost

Original Research

N-(Phosphonomethyl)glycin (glyphosate), known by the trade name of Roundup®, is a broad-spectrum systemic herbicide used to kill several types of grass weed. It was first synthesized in 1970 by J. E. Franz, a chemist at the agrochemical corporation Monsanto. Glyphosate's mode of action is to inhibit a plant enzyme involved in the synthesis of some aromatic amino acids. There is some controversy at present about the use of Roundup® because its hazard potential is not clear. In this article, we present some reliable and easily performed spectroscopic and electrochemical measurements to identify glyphosate isolated as well as in some commercial products. The analogous experiments apply to (Aminomethyl)phosphonic acid (AMPA), the hydrolysis product of glyphosate.

World Journal of Chemical Education. 2015, 3(6), 134-140. DOI: 10.12691/wjce-3-6-2
Pub. Date: December 03, 2015

Full-Text PDF

29158 Views7255 Downloads2 Likes1 Citations

Teaching Chemical Equilibria Using Open Source Software OCTAVE

by Juan José Baeza-Baeza, Francisco Fernando Pérez-Pla and María Celia García-Álvarez-Coque

Original Research

The use of computational software can greatly facilitate the teaching of chemical equilibria. It allows the treatment of complex problems without the need of simplifications, and the outcome of a very large number of calculations in a short time. Two practical examples of different complexity are proposed in this work to show the application of a general systematic approach for the numerical calculation of multi-equilibria problems, regardless of the number or types of equilibria involved. The method consists in writing down a system of non-linear equations formed by equilibrium constant expressions and the needed number of conservation balances so to match the number of chemical species involved. The exact solution of the system of non-linear equations describing the multiple equilibria is obtained by means of the fsolve tool of the open source software OCTAVE. The approach also allows multiple calculations by automatic changing of the initial conditions. The graphical representation of the concentration of chemical species is also possible as a function of selected variables, such as the initial concentration or the volume of a given reagent.

World Journal of Chemical Education. 2015, 3(6), 127-133. DOI: 10.12691/wjce-3-6-1
Pub. Date: December 01, 2015

Full-Text PDF

21102 Views6382 Downloads5 Likes1 Citations