Revival of the oxidation number method for balancing redox equations

Abstract

A study published in 2009 involving first-year students at Tshwane University of Technology in Pretoria, Republic of South Africa, showed that most of the students at that institution were not able to balance chemical equations satisfactorily. For balancing relatively complex redox equations, the oxidation number method is found to be the simplest method. However, it appears to the author that the number of professors who teach this method is strictly decreasing, which will ultimately cause the method to be extinct. One reason for its apparent gradual disappearance might be that many students have not learned the oxidation number method well. In this article, with the aim of reviving the method, redox equations are classified into three classes referred to and discussed as Class I, Class II and Class III, based on how exactly the method is applicable to balance the equations. In light of the solid theoretical foundation and the systematic educational classification presented, this article will hopefully serve as an encouragement to chemical educators to teach the method, so that its use can continue.

Keywords:

• balancing
• chemical education
• oxidation number method
• redox

ACKNOWLEDGEMENTS

Aliyar Mousavi would like to thank Mr Spencer Trafton, student at Nashua Community College, for his assistance in the preparation of Figure 1; Ms Kirsten Boucher, Laboratory Assistant at Nashua Community College, for her assistance in taking the picture of the mercury(II) sulphide shown in Figure 1; and last, not least, the author would like to give special thanks to Mr Es’haagh Asadi-Nasrabadi, chemistry teacher at Imam Mousa Sadr High School, Tehran, Iran, in 1991–1992, for teaching the oxidation number method efficiently.