World Journal of Chemical Education

A teaching approach is proposed inspired by the hierarchical structure of the neon electron configuration. The course material is organized into analogous hierarchical 1s (molecular structure and physical properties), 2s (oxidation level based reaction schemes and acid-base) and 2p (three pairs of reaction mechanisms) course modules. The connection between acid-base and oxidation-reduction in organic chemistry is made clearer. General options, instructor’s knowledge structure, building on prior knowledge, educational success, the value of the approach and the support from the educational research are discussed.

World Journal of Chemical Education. 2015, 3(2), 51-58. DOI: 10.12691/wjce-3-2-5
Pub. Date: May 06, 2015

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Application of ¹H-NMR for the Quantitative Analysis of Short Chain Fatty Acid Methyl Ester Mixtures: An Undergraduate Instrumental Analysis Experiment

by Ronald. P. D’Amelia, Ling Huang, William F. Nirode, Eve Rotman, Jayni Shumila and Nanette M. Wachter

Original Research

Nuclear magnetic resonance spectroscopy (NMR) is one of the most important instrumental techniques used to elucidate the molecular structure of organic compounds. However, there are not many good simple applications of using NMR for the quantitative assay of impure or mixtures of organic substances. The current experiment was developed as part of an ongoing effort to increase exposure to quantitative proton NMR methodology in the undergraduate chemistry laboratory curriculum. The objective of the experiment is to determine the percent composition of a two component mixture of short chain fatty acid methyl esters using chemical shift and integration values obtained from running solvent-less samples both with and without an internal reference standard. We report on the experimental methods and results obtained from examining the quantitative NMR properties of a series of mixtures of methyl acetate (M.A.) and methyl propionate (M.P.) solutions ranging from 100% MA to 100% MP. Also similar data was obtained for the MA - methyl butyrate (MB) pair. The results exhibit a linear relationship of the percent composition of the methyl acetate binary mixtures found by proton NMR with the theoretical (i.e. samples prepared based on measured weights) percent compositions. The experiment confirms the quantitative usage of ¹H NMR and serves as an educational tool for the undergraduate chemical laboratory.

World Journal of Chemical Education. 2015, 3(2), 46-50. DOI: 10.12691/wjce-3-2-4
Pub. Date: April 22, 2015

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Accurately Precise and Precisely Accurate: An Experimental Comprehension

by Shaikh. Mohiuddin and Zahida Karim

Original Research

Accuracy and precision are the primary targets in chemical analysis. This article is an experimental approach to appreciate the concepts of precision and accuracy in analytical chemistry. An easy, fast and well-established spectrophotometry experiment for quantitative analysis of Fe²⁺ is done using 1,10-phenanthroline as a complexing or coloring agent. Real time learning approach is carried out; it means discussing the data in front of class after collection of experimental results. A little data is used to discuss variety of concepts of basic statistics in analytical chemistry. A debate regarding priority of precision over accuracy is done. The objective of using standard deviation (STDEV) and changes in its value by unit conversion or other transformation is explained. The advantage of using relative standard deviation (RSD) is also demonstrated. Several spectrophotometers are compared regarding precision. By using same data, precision of analog and digital spectrophotometers is also compared. Repeatability and reproducibility are also explained and calculated using the same data. Presence of systematic error or accuracy of experiment is statistically assessed without doing further experimentation. The whole study is optionally supported with online MS-Excel worksheets that are automated for better understanding.

World Journal of Chemical Education. 2015, 3(2), 40-45. DOI: 10.12691/wjce-3-2-3
Pub. Date: April 22, 2015

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Using Simulation of Apparatus Set-up to Improve Safety

by Brahmadeo Dewprashad and Colin Persaud

Original Research

There is increased focus on improving both safety and learning outcomes of undergraduate chemistry laboratory experiences. Incorrect setting and/or misuse of equipment occurs commonly and can even lead to accidents. This article describes how this was addressed by the development of pre-lab activities that require students to read a detailed step by step word document with instructions and appropriate diagrams describing the set-up of the apparatus, watch a video demonstrating the same and then demonstrating that they could set-up the apparatus by successfully completing an online simulated assembly of the apparatus. Following the pre-lab activities, students undertook the lab and were required to set up the apparatus on their own but to seek instructor’s help as needed. It was observed that the class was able to set-up the apparatus within fifteen minutes. This is in contract to the usual time of around one hour taken traditionally. The time saved was used was used to link the theory underlying the lab to a novel application of nanoparticles to accomplish distillation at room temperature. Students were also surveyed on their perception of the pre-laboratory activities. An overwhelming majority of the students felt that the pre-lab activities were valuable and better prepared them to set-up the simple distillation apparatus correctly and that similar pre-lab activities be developed for other laboratory exercises.

World Journal of Chemical Education. 2015, 3(2), 36-39. DOI: 10.12691/wjce-3-2-2
Pub. Date: April 16, 2015

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Metallic Structure and Bonding

by Peter F. Lang and Barry C. Smith

Review Article

This article briefly describes the current physical model of metallic structure and bonding. An alternative soft-sphere model of metal structure is introduced. Limitations of the current model are given and properties of metals which can be accounted for by the soft-sphere model are discussed. A simple soft-sphere formula, which calculated internuclear distances of Group 1 and Group 2 crystalline binary salts to a remarkable degree of accuracy, is applied to calculate metallic radii (equal to half the internuclear distances) of Group 1 and Group 2 metals precisely. A simple expression previously used to calculate lattice energies using the soft-sphere radii concept is used to calculate enthalpies of formation of Group 1 and Group 2 metal ions and results compare well with observed values. The work functions of Group 1 and Group 2 metals are shown to be inverse functions of the soft sphere ionic radii.

World Journal of Chemical Education. 2015, 3(2), 30-35. DOI: 10.12691/wjce-3-2-1
Pub. Date: April 02, 2015

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