Authors: Radhakrishnamurty Padyala
The fundamental law of chemistry – the law of stoichiometry - is not properly understood even after two centuries of existence. The significance of the pivotal concept of ‘equivalent of a reaction’ is not recognized. This led to several misconceptions that include ‘what a chemical reaction is’. The origin of the problems lies with lack of understanding of the distinction between a mixture of chemical reactions represented by the equation: ∑αi Xi = 0, and a chemical reaction represented by the equation: ∑νi Xi = 0. νi ≠ αi; (νi is the stoichiometric coefficient of species Xi and αi is a rational number),. These problems are easily identified in the decomposition and combination of chemical reactions (that includes half cell reactions), specifically in case of disproportionation reactions. In these cases we find multiple values of zcell (equivalents per mol of reaction) and properties such as E0 (standard potential) for a given reaction. This is a paradox. It is impossible a for reaction under given conditions to have multiple values of a property (a thermodynamic state function). We critically analyze these issues and highlight in this paper the crucial aspects of a chemical reaction: That it must have a unique number of equivalents per mol, must be decomposable uniquely into two partial or half cell reactions, must be obtainable from combination of two partial or half cell reactions in a unique way; and, the distinction between a chemical reaction and a mixture of chemical reactions. Our analysis leads to: a new definition of chemical reaction; a new definition of linearly independent reactions, a new relation between the number of equivalents per mol of the partial or half cell reactions and the resultant chemical reaction; specify the two necessary and sufficient conditions to be satisfied in combining reactions to get resultant reactions. We apply the criteria to a few examples to show their applicability. We also comment on Avogadro number and the terminology - ‘kJ per mol of reaction as written’. Chemistry must play an active role to bring back the preeminent role of chemistry in furtherance of natural sciences.
Comments: 12 Pages.
[v1] 2016-12-27 02:01:39
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