World Journal of Chemical Education

Most of the laboratory experiments of undergraduate chemistry curriculum are based on pH metry for qualitative and quantitative analysis. Establishment of any acid’s profile in terms of it being mono, di, or triprotic is a common trend in lab exercises. In these tasks, experiments are designed to classify multiprotic acids in terms of their stepwise proton releasing capability. Strong acid-base pH titration curves have such equivalence and inflection points that could be identified with ease. However, some multiprotic weak acids have such equivalence or inflection points which are difficult to identify from the titration curves, developed during these lab experiments. Hence students arrive at inaccurate conclusions. This difficulty appears when nothing is apparent from the experimental curve that the acid in question is mono, di, or triprotic. The purpose of this study is to describe the method for prediction of the strength of such weak multiprotic acids, which are difficult to be classified in terms of their multiprotic nature. An acid base titration may be employed to evaluate acid’s equivalent weight provided one is able to fix its multiprotic behavior. The experimental approach that is presented here, highlights the suitability of equivalent weight based calculation to establish the multiprotic nature of any weak acid whose inflection point is difficult to detect in titration curves due to very close values of their successive dissociation constants.

World Journal of Chemical Education. 2016, 4(1), 21-24. DOI: 10.12691/wjce-4-1-4
Pub. Date: April 18, 2016

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Investigations of Some Reliable Electrochemiluminescence Systems on the Basis of tris(bipyridyl)Ruthenium(II) for HPLC Analysis

by A. Habekost

Original Research

Electrogenerated chemiluminescence (ECL) is not only an aesthetic phenomenon, but also of fundamental interest in analytical chemistry Several experiments are presented to introduce students to the capacity of ECL on the basis of tris(2, 2’-bipyridyl)ruthenium (II) (Ru(bpy)32+) with different coreactants.. First, we summarize some spectroscopic and electrochemical features of Ru(bpy)32+ that are important concerning ECL. Easily implemented experimental set-ups are presented, which show the correlation between ECL-intensity and cyclic voltammetry (CV) for different Ru(bpy)32+ / coreactant systems. The time-dependence of the ECL-decay is measured on a millisecond time-scale with a conventional data acquisition system. Finally, we present an ECL detector that can be used in HPLC as an alternative to adsorption and fluorescence detection.

World Journal of Chemical Education. 2016, 4(1), 13-20. DOI: 10.12691/wjce-4-1-3
Pub. Date: April 08, 2016

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Experimental Investigations of Alkaline Silver-zinc and Copper-zinc Batteries

by A. Habekost

Original Research

Batteries are important issues in electrochemistry and in electrochemistry lessons. But nevertheless, the electrode processes in batteries are not quite easy to understand.One of the didactic benefits of the investigations of alkaline silver-zinc and copper-zinc batteries might be the chance to directly observethe changes on the electrode surface and the simple way to measure the electrode processes. These electrode processes are intensively examined so that they can be explained well and described clearly.In this paper we will present several experiments to investigate these two battery systems: Cyclic voltammetry is used to identify the electrode processes, and on the basis ofcharging and discharging curves one can estimate the efficiency of the batteries. Furthermore, the reflection of a laser beam onto a surfaceis an easy means to correlate the results with the electrochemical changes of the electrode.

World Journal of Chemical Education. 2016, 4(1), 4-12. DOI: 10.12691/wjce-4-1-2
Pub. Date: January 05, 2016

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Dynamic Representation of Organic Chemical Reaction Mechanisms with Animated Lewis Structures

by J.-H. Wilhelm

Original Research

Animations and Simulations are suitable to explain chemical facts. In 2011 the new 2D structure editor MyChemise was introduced by the author. After upgrading to a new version the software is now offering the possibility to export animations as gif files. Through the use of 2D animations, it is possible to visualize depictions of reaction mechanisms for digital media. With the free available software MyChemise they can be developed in a simple manner within a relatively short amount of time. The exported gif files offer many ways to make use of the animations. In Wikipedia articles, these animations illustrate the chemical processes described in the text and complement conventional sketches. The new kusGifViewer allows to control the representation for educational purposes.

World Journal of Chemical Education. 2016, 4(1), 1-3. DOI: 10.12691/wjce-4-1-1
Pub. Date: January 04, 2016

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